Numbers of this bird are falling and, unusually, more individuals die during spring and summer than they do in the autumn? But why is that?
Words: Dominic Couzens
It is almost an article of faith among us to think that birds struggle to survive in the winter, with all its challenges, such as frost, snow, cold and starvation. In which case, I have got a surprise for you. The Lesser Spotted Woodpecker, our smallest bark-tapper and a bird whose population is plunging throughout Britain, does not struggle. In fact, it positively thrives; its cold-season mortality is almost negligible. If birds expressed a preference for season, the Lesser Spotted would plump for winter every time.
There are several reasons for this. One is that, from October through to March, the Lesser Spotted feeds almost entirely on insects and their larvae obtained from boring wood (along with the occasional visit to a garden bird feeder.)
So long as there is enough dead or decaying wood around, the woodpecker manages just fine. Apparently, the surface of bark is one of the most reliable habitats there is. In contrast to many small bird species, Lesser Spotted Woodpeckers also have no problems with finding a roost site – they simply dig their own hole. Food and shelter are sorted.
The birds don’t have problems with overcrowding, either. Have you ever worried that a site has too many Lessers for the space? Of course not.
These midgets are found at naturally low densities, as anybody who has tried to find one knows only too well. A study in Norway found that, on average, an individual occupies a home range of 742 hectares in the winter. Winter, then, is blissful. The Lesser Spotted’s needs are all covered. In many instances, any pairs that have successfully bred the year before remain in close proximity right through the season, living more or less as a couple, albeit with separate beds (roosting holes.)
There is evidence that, chivalrously enough, the sexes divide the foraging habitat between them, the females foraging on smaller-diameter trunks and branches, and the males specialising in bark-stripping and pecking, while the females specialise in probing. The picture is happy and harmonious.
But there could be trouble ahead. There have been many recent studies conducted on Lesser Spotted Woodpeckers, many of them probing into the reasons for its decline, down more than 60% in the 30 years to 1999, and perhaps even faster since, and they all reach the same broad conclusion. Breeding is tough for these birds, most especially the females.
As already mentioned, more individuals die in spring and summer than they do in the autumn. And even when they do survive, adults quite often abandon their breeding attempts in the middle, seemingly unable to cope.
The picture could almost be painted of a pair of woodpeckers having a look at the fading daffodils, exchanging glances, sighing and thinking: “Let’s just not bother.” And while this is obviously fanciful, a study in Sweden found that a significant number of pairs held territory, alright, but didn’t even get as far as laying eggs – the proportion was as high as 22% in one year. That figure, approaching a quarter of all pairs present, is unusually high.
And it is often the weather that determines this. For a bird that breezes through the coldest months, it seems odd that the Lesser Spotted Woodpecker might suddenly become susceptible to inclement conditions in spring and summer. This, though, is exactly what does happen. The birds just cannot function as breeders when it is cold and wet, despite the fact that the species itself occurs well into the sub-Arctic taiga belt throughout Europe and
Asia. It seems that they suddenly go soft.
In truth, it is hardly unusual for birds as a whole to suffer during poor weather in the breeding season; exactly the same thing occurs in many common species, such as Blue and Great Tits. In these birds, the cold weather restricts the ability of the female to get properly into condition to face the rigours of breeding, and then makes it hard for both parents to forage for their nestlings.
In the case of Lesser Spotted Woodpeckers, it is frequently the first stage that proves insurmountable.
Imagine, then, that you were a social worker for pairs of Dendrocopos minor and it was your job to examine conditions at home. Time and again you would find that, throughout the early season, whatever the weather, the females were suffering, and the males were trying to bail them out.
The heaviest burden of work often falls upon paired males. It is they that do most, if not all, of the nest-building, on average 65%. They incubate more than the female does, taking the whole night shift and half the day shift.
Unusually, they also do more brooding of the hatched young; again, this is throughout the darkness and for half of the day. And they often end up feeding the young more, too. The regular routine of Lesser Spotted Woodpeckers incorporates an extraordinarily unbalanced division of labour.
Despite the male’s best efforts, still the females struggle. In one study, at a remarkable 42% of nests, the female abdicates feeding young during the late nesting stage, when the young are almost ready to leave. For a week or so she forages for herself and, if all goes well, will often resume helping when the young have left the breeding hole.
Even when both sexes feed the young for the duration, the male still brings in food more often, 6.9 times an hour as opposed to 5.6 times an hour.
Over the course of the last 10 days of the nestling period, from which these measurements were taken, that is a significantly greater effort. The truly odd thing about this is that these small woodpeckers are feeding themselves and their young on an abundant food source at a premium time.
This species impeccably times its egg-laying with the bud-burst of oak leaves in a wood, which should allow the habitat to overflow with food when the young hatch.
Yet, despite bringing a wide variety of insect food to their chicks, including moth caterpillars, aphids and beetle larvae, this period of life is truly fraught.
Perhaps not surprisingly, females sometimes take an unconventional route to success by pairing simultaneously with two males at a time and using two nests – this occurs in 10-20% percent of cases. It certainly solves a female’s troubles: individuals so paired produced 39% more young. This, though, only occurs when the sex ratio is already skewed. On the whole, these woodpeckers are extremely faithful to their mates, with a ‘divorce’ rate of only 3%. Established pairs are invariably more successful in a season, compared to individuals trying for the first time. However, even in these instances, the males are much harder-working than the females.
As previously mentioned, this delightful bird is seriously declining in Britain, and is now down to about 1,500 pairs, countrywide.
Nobody is quite sure why it is happening, although one possibility is that the males are unable to compensate for the struggles of the females, maybe because of a general decline in habitat quality, with less dead wood available.
Whatever the reason, we might one day have to write a Requiem for D. minor. It won’t, though, be a winter’s tale.
Dominic Couzens on Mistle Thrush
Mistle Thrush fact-file
Scientific name: Tardus viscivorus
UK numbers: 170,000 breeding territories
Diet: Insects, berries, worms and slugs
This is the thrush that embarrasses birders. It’s the large, barrel-chested spotty-breasted one that ought to be simple to identify, but somehow isn’t.
It perches high on the branches of trees in early spring, seemingly always with its body angled away, or with a branch in front of it, so we cannot quite see its features properly. It is the thrush that sings, but never quite clearly or close enough for us to be sure. It isn’t the poet Robert Browning’s bird: “That’s the wise thrush; he sings each song twice over.” Instead it’s a wise thrush that makes fools of us all.
For a large, bold bird with seams of aggression stitched into its character, a bird of dominance which can scatter smaller beings when it lands nearby, the Mistle Thrush is a remarkably overlooked species. It is found almost all over Britain, yet is barely noticed. Who would have thought that the species was once involved in a large-scale, Collared Dove-like invasion of swathes of the country?
Admittedly, it was long ago; just before 1800, the Mistle Thrush was all but confined in this country to the south, but then something caused it very rapidly to spread all over northern England and Scotland over a few decades, until by 1850, it had conquered the whole realm.
The BTO’s Bird Atlas 2007-11 records breeding in 96% of the 10km squares covering the British Isles. While we conquered Napoleon, parts of our country were quietly being invaded.
Low density breeding
It would have been invasion-lite, however. It is not as if we readily see a Mistle Thrush at every street corner. It has long been recognised that British Mistle Thrushes breed at bewilderingly low density.
One well-studied suburban plot held 180 pairs of Blackbirds, 12 pairs of Song Thrushes and just one pair of Mistle Thrushes, while a broad estimate suggested that the density of Mistle Thrushes is only 10% that of Blackbirds. The impression is that there is plenty of room to expand, and the larger thrushes are not as numerous as they should be.
There are some explanations for the low density. In contrast to Blackbirds and Song Thrushes, Mistle Thrushes don’t tend to feed among leaf-litter, preferring open grassland, instead.
Furthermore, they generally eschew the patchwork of small gardens that make up suburbia, needing wider expenses of sward to feed comfortably. They also prefer tall trees for nesting. Despite these drawbacks, they still could be more abundant. And this is particularly odd when you bear in mind that, in some parts of the continent, Mistle Thrushes can be colonial.
Most pairs nest singly, but in countries such as Denmark, Germany and Russia, some do breed in close proximity. For some reason, this just doesn’t seem ever to happen here.
The low density of breeding pairs ensures that it is always a treat to hear the song of a Mistle Thrush percolating through the soundscape of a neighbourhood. Some consider it one of the finest of British bird songs, combining the Blackbird’s virtuoso content with the Song Thrush’s proclamatory style.
It does combine elements of the two, with a repetitive style redolent of Song Thrush but with tone closer to Blackbird. Listen long enough, however, and you can pick up its own unique flavour.
It has an unforgettable melancholy quite lacking in the other two species, and the singer also has a curious knack of sounding much further away than its actually is. Invariably, it stays longer on its perch than the other thrushes, almost always close to the very top of a lofty tree.
Famously, it seems unperturbed by inclement weather, and will sing lustily in the rain and wind, when most other birds take shelter. I am not sure there are any statistics indicating that Mistle Thrushes sing more often than other thrushes in challenging meteorological conditions, nor indeed that they sing more frequently in the afternoon, as is claimed. Perhaps these impressions stem simply from the reality that Mistle Thrush phrases are easily drowned out by other songs? But it would take a hard heart not to be stirred by the wild, haunting utterances from the ‘Storm Cock’, fighting against an irksome wind on a stuttering spring day.
Another strange fact about Mistle Thrush songs is that, at least in some places, they apparently are given in flight. This isn’t an aberration but instead, in Germany and elsewhere, it is a routine phenomenon.
Personally, I have never seen this, and I don’t know anybody who has; neither do the usual bird books over here refer to it. Yet sometimes the bird evidently launches into the air and sings as it goes, as a Cuckoo often does. This aerial aria seems to be a continental oddity.
And what about their courtship-flight? Have you ever seen that? Again, though, it has been recorded in the literature many times. The choreography is similar to that of the Robin’s early courtship, the ‘song-and-following’; the male sings, the female darts away, the male follows and sings, and so on.
Sometimes the (presumed) male flies around the potential mate and shows off his gleaming white underwings. Usually concealed within tree branches, this ceremony is undoubtedly an early spring secret, unknown to most of us.
One piece of behaviour that is much easier to observe, however, is the Mistle Thrush’s aggression, coupled with its very loud, discordant calling, an angry and irritable rattle. While this is sometimes triggered by the presence of a bird of prey or other danger, or by the unwanted presence of rivals, look closely and you might see that it is frequently all about berries.
You might have thought that squabbles over fruits might have finished by the end of autumn, but the fact that they can rage now, in late winter and early spring, unveils another interesting pastime of our largest thrush, the sequestration of fruity assets.
Mistle Thrush: A half-understood species
While many thrushes, such as Redwings and Fieldfares, spend the winter passing nomadically from district to district feeding upon berries that they come across in serendipitous fashion, some singles and pairs of Mistle Thrushes take a different approach to foraging.
They select a tree or trees that have a crop of long-lasting fruits, such as Holly berries, and remain close by them, driving away any visitors that arrive to take advantage of the crop.
Such is the dominance and intimidatory manner of Mistle Thrushes that, for months on end, they can keep rivals of other species at bay, unless there is a sudden arrival of a large flock.
So long as that eventuality doesn’t occur, the birds can ensure the preservation of a significant, personal food-supply for them to pluck whenever they wish – and when it is mild, they can feed on soil invertebrates while keeping watch on their inheritance.
Their actions mean that Mistle Thrushes will often have a useful crop of berries available to feed themselves and their subsequent young well into the spring. It works so long as they are vigilant and suitably petulant when challenged. And yet, as so often with the Mistle Thrush, this isn’t the whole story.
Some individual Mistle Thrushes undertake long-term fruit-defence, while others don’t at all, but are nomadic. What causes some to be sedentary and others to move isn’t known.
And we don’t fully understand the song-flights, or the nest-dispersion, nor do we understand the nature of late-summer flocks. We don’t understand why Mistle Thrushes typically nest very early, with eggs in March, either.
True, the Mistle Thrush is often a half-seen and half-identified bird, of annoyance to many a frustrated birder. But, surely, to scientists, it is also a half-understood species.
Where to see Mistle Thrush
A bird widespread across the UK, it can be found almost everywhere but is absent from the highest, barest ground and also from the northern and Western Isles of Scotland. Look in gardens, woodland and parks.
By Dominic Couzens
You can imagine the scene. A Hawfinch perches upright in a tall forest tree, looking out over the canopy, well out of sight of any human being. As with every bird, everywhere, it is hungry, and here among the twigs and branches of its favourite woodland giant, it knows there is plenty of food.
After a brief glance down, it manoeuvres its massive bill, opens the mandibles and plucks what it needs – a juicy caterpillar. Hang on, is that a mistake? A Hawfinch is eating a caterpillar? Is this the same Hawfinch that is famous for little more than having an outsize bill, capable of exerting enough force to crack a cherry kernel, or even an olive stone? Yes, this is the same species, alright. But this is the surprising Hawfinch, the real bird, which has a quiet lifestyle that very few people know about.
In the summer, oddly, it almost entirely forsakes its winter diet of nuts and fruits and feeds instead on soft-bodied invertebrates. The famous bill, its prized asset, is rendered less useful than usual and might even be a hindrance at such a time. But in the summer forest canopy, insects roll off the trees and times are easy, so the specialist becomes a temporary member of the ranks of ordinary insectivores, competing with Blue Tits and flycatchers.
Young Hawfinches, in their first few weeks of life, must wonder what their bill is actually for. Of course, the Hawfinch’s mandibles do come into their own in the depths
of autumn and winter, when seeds are everywhere.
With so many species competing for the nutrition they bring, it pays to have an dvantage, and the Hawfinch bill is simply more powerful than that of any other finch, allowing it access to larger and harder seeds and stones. And while the sheer size of the bill is what every birdwatcher can see, easily, it is the internal structure that is the marvel.
Finches are defined by their bills, and the family as a whole is highly adapted for de-husking of seeds. Just inside the rim of the outer (cutting) edge of a finch’s upper mandible is a sharp bony ridge which juts out below the palate, but not as low as the outer edge – the arrangement is like the two ridges of a molar tooth.
Hawfinch: packed with muscle
Using its tongue, a finch can lodge a seed in the gap between the cutting edge and the inner ridge. Meanwhile, the cutting edge of the lower mandible articulates into this gap, meaning that the sharp point of the lower mandible pierces the husk of any seed that is lodged there. A quick roll of the seed with the tongue peels off the pierced husk.
Hawfinches have this arrangement, but in addition their bills have a pair of bony, serrated protuberances at the back of both upper and lower jaw, either side of the mid-line of the bill. Once clenched on a seed, all the strength of the muscles closing the bill is concentrated on these four knobs jutting on to the husk.
It is this concentration of force that causes the seed casing, however hard it is, to rupture. And what force it is. Scientists have measured the crushing force of a Hawfinch bill and found it to exceed 50kg, which is a weight equivalent to more than twice the baggage allowance an airline might allow you. Think of those heavy bags at the airport and you will appreciate the extraordinary might of a bird that itself weighs only 0.05kg.
No wonder this finch has such a large, bulging head, packed with all that muscle. It is a bird that could, if circumstances allowed, probably crush your finger. Perhaps surprisingly, the bill isn’t the only part of a Hawfinch that is physically unusual. If anything, the flight feathers are even odder, indeed unique.
Too much bird bling?
The four inner primary feathers are a completely different shape to the conventional outer primaries that make up the wingtip. They are shorter than they ‘should’ be, truncated in length and curved at the ends. The secondaries are also slightly curved and, when the bird is perched, the wing looks somewhat damaged. It is hard not to think that this bling must impair the birds’ flight. Hawfinches are top-heavy and awkward in flight as it is! But what is the function of these ornaments? It is widely assumed that they play a role in sexual selection, since the modifications are more strongly pronounced in males than in females and, more tellingly still, are most fully developed in older, presumably socially dominant males. They are shown off in the subtle displays of Hawfinches
in winter flocks, the scene for pairing up. Males ruffle their plumage and droop and spread the wings, and these wing manoeuvres are not seen in other members of the finch family.
Hawfinches also have an unusual ‘bill-touching’ display, in which the prospective pair lean over to touch the tip of each other’s bill, almost falling over while doing so. Another of the many curiosities surrounding this magnificent bird is the fact that it is so unobtrusively quiet. In the spring the woodlands resound with Chaffinch song, gardens fizzle with Greenfinch song and hedgerows chatter with the efforts of Linnets. But the woodland canopy remains quiet.
Hawfinches do have a song, but it is soft, halting and unmusical, barely worth the effort – and besides, it seems that its function in pairing up and holding a territory is minimal.
You hardly ever hear it. The call note, a loud, slightly spitting ‘pix’, is also easily missed, so much so that this bird, shy and quiet for most of the time, is famously difficult to find.
A peculiar quirk of Hawfinch breeding behaviour is that there are two quite different types of ‘housing’. Some pairs nest entirely alone, hundreds of metres away from anybody else, seemingly alone in their ‘country estates’.
Others, however, the more successful birds, nest together in what be described as desirable cul-de-sacs, with a reasonable gap between nests (a few tens of metres), but in definite clusters. The reason for this distinction in breeding density isn’t known. As mentioned at the start, young Hawfinches in the nest are fed mainly on soft-bodied invertebrates, together with some seed paste crushed in the parents’ bills. This is fed bill-to-bill by both sexes.
When the young leave the nest, they may stay with their parents for much longer than most young finches do, because the unusual bill takes time to develop. It is some months before the first-year birds can handle tough seeds – indeed, they might not be proficient until deep into the winter. Thus, if you see a flock of Hawfinches this winter, you might actually be seeing one or more family parties, because in addition to the young sticking around for a while, members of a pair frequently overwinter together.
In common with most finches, they are highly sociable, although they form only modestly sized flocks. Last autumn was a bumper year for Hawfinches in Britain, with much large numbers than usual flocking to our shores.
It is a great time of year to see this charismatic and colourful bird, a species which can be very surprising in many aspects of its lifestyle.
Scientific name: Coccothraustes coccothraustes
UK numbers: 500-1,000 breeding pairs, 10-15,000 wintering birds
Habitat: Deciduous and mixed woods
Diet: Buds, seeds and shoots
By Ian Parsons
The House Sparrow, thanks to deliberate and not so deliberate introductions, is the most widely distributed bird in the world. In Britain, we have a population of more than five million pairs, making them one of our commonest species; they are familiar to us all, whether we live in the heart of the city or deep in the countryside. Yet, if you look at the data, these are birds that are in big trouble, especially in England. So what is going on with the House Sparrow?
The sad truth is that this common bird has experienced a drastic decline in numbers since the 1970s, it may still be a common bird, and a population of more than five million pairs sounds impressively large, but when you compare it to the 12 million pairs that we had in Britain in the 1970s you start to see there is a problem. A big problem.
If the humble, ubiquitous Sparrow continues to decline at that rate it will be extinct in Britain within my lifetime. Surely, as I sit here writing this, listening to the House Sparrows in my garden squabbling over the food, that can’t happen, can it? The House Sparrow’s native range is large, extending throughout Europe and into Russia and Asia, down into the Middle East and the Arabian Peninsula, as well as encompassing India and Bangladesh. Thanks to deliberate introductions, the bird has spread right across the globe.
In America, it was first introduced from England into New York City to control the caterpillars of the Linden Moth which were ravaging the many Lime trees planted within the city.
This wasn’t the best of plans, not least because, other than when they are feeding their chicks, the diet of the House Sparrow is very much seed-based (although they have now readily adapted to exploit our untidy ways when it comes to rubbish and food) and not caterpillar-based!
House Sparrows have proven themselves to be prodigiously invasive. It was first introduced into New York in 1863 and is now the most abundant bird in North America, being found everywhere from the Arctic-hugging Northwestern Territories of Canada, down to the tropics of Panama. Just seven years after that North American introduction, House Sparrows were introduced to South America, being released in Buenos Aires, Argentina in 1870.
Nowadays it can be found right at the southern tip of the continent, in Tierra del Fuego, and all the way up the Andean coast almost meeting up with the North American birds in Panama.
Other introductions in Tanzania in 1900 have led to the bird being found across a large part of southern Africa and, following an introduction in 1863, most of eastern Australia is now home to these small birds. Once they have been introduced, House Sparrows are able to increase their range at an astonishing rate, sometimes expanding it by 140 miles a year!
The House Sparrow, therefore, is a bird that can do extremely well in a variety of habitats. It is able to expand rapidly and is able to live alongside man in country and urban situations throughout the world. That makes the fact that the bird has had such a sharp decline in Britain extremely worrying; if the House Sparrow is struggling in Britain, what chance have other birds got? The House Sparrow is a brilliant little bird, but because it is so ubiquitous, so well known, it isn’t always appreciated, even by us birdwatchers, who can often be very dismissive of them when out birding.
The fact is they are a very interesting species and because they are still relatively common and often live in close proximity to us they are an excellent species to study. Being able to watch a bird closely allows us to identify many aspects of bird behaviour. What better bird to practise your birdwatching skills on than the House Sparrow?
Studies have shown that this small bird is actually long lived for its size, with one bird in Denmark living for at least 19 years; the typical lifespan is between three and four years.
This may seem low, but similar sized birds such as Dunnock and Robins have a typical lifespan of two years. House Sparrows form strong pair bonds, and are essentially monogamous. However, as is typical of many so called monogamous bird species, about 15% of the chicks that fledge are the offspring of a different male from the male bird of the pair.
Not all the birds in a breeding population form pairs, though, and these unpaired birds often act as helpers to the paired ones, helping them raise their broods. This help is probably very important, as a breeding pair will often have three broods (sometimes four) of four-five chicks per brood, and without it, it is questionable whether the House Sparrow could be such a prodigious breeder.
As already mentioned, House Sparrows have a diet of mainly seeds, but the young in the nest have a diet of insects. They cannot survive on dry seeds, and as they have no access to water while in the nest, they get their moisture from juicy insects, which are also packed with vital protein.
Many of our insect-feeding bird species have shown population declines as the sparrow over the same period and there is no doubt that our abundance of insects in Britain has been severely diminished in recent years.
As a child, I remember what we used to call ‘Insect Rain’ – the splatter of insects hitting the car windscreen as you drove along on summer evenings – making a real mess of the windscreen and front of the car. This still happens in many parts of Europe, but you may have noticed that it hardly ever happens in England now. The intensification of agriculture and the subsequent development of newer and more lethal insecticides are blamed.
Fewer insects in the environment means less birds that depend on them. Changing agricultural practices are more than likely the cause of the decline of Sparrows in the countryside, but House Sparrows are also declining in our cities and urban environments, too. In fact, the decline in these areas is more rapid than the decline in the countryside, at the moment no one is quite sure what is causing this decline, but it is extremely worrying.
They might not be yellow and they might not sing a pretty tune, but if such a successful bird is declining in our urban environments then perhaps they are fulfilling the role of the canary in the coal mine, warning us of impending danger.
House Sparrows may be very common, we may see them regularly, but we most definitely cannot take them for granted. They are in trouble, and that should concern us all.
House Sparrow fact-file:
Scientific name: Passer domesticus
UK numbers: 5,300,000 breeding pairs
Habitat: Varied, from cities to farmland
Diet: Seeds and scraps
By Ian Parsons
It won’t be long before the species that won last year’s Vote for Britain’s National Bird will be staring at you from the corner of your living-room. The Robin, quite possibly hopping around in the sort of snowfall we rarely see in December, and maybe even sporting a Santa hat, will be the star of a good many of the Christmas cards that you receive.
We’ll talk about the reasons for that seasonal association later, but, in fact, Robins will already have been stealing the show for several months. There are many indicators that summer’s over, autumn has been and gone and winter is here.
From the leaves of Ash trees turning yellow, to the sloes on the Blackthorn darkening to a deep purple and the Swallows and Martins gathering on the wires in ever-increasing numbers, nature heralds the turning of the seasons in several different ways. But for me, nothing beats the autumnal and winter song of the Robin.
Winter singing is unusual in British birds, but the Robin’s melancholic song is heard throughout the country as the temperatures drop. With other birds quiet, it is a great time to really get to know the song of this common bird. It is a melodic, fluty song, beautiful and sad at the same time. With everything else quiet, the beauty of the song seems extra special.
So why are they singing? Well, as in the spring, it’s to establish a territory, but, unlike in spring, they’re not singing to attract a mate to it. This territory is not for sharing. The Robin is well known for being a belligerent defender of its territory, and in early autumn they’re at their most aggressive as they compete with one another to establish the ownership of their autumn and winter quarters.
Robins defending their territory
It is estimated that 10% of all adult Robin deaths are caused by other Robins, and it is when the birds are establishing their autumn and spring territories that these fatalities are most likely to occur. A Robin singing on a cold morning may well be music to our ears, but it can be very dangerous for other Robins nearby.
If the birds are not looking to attract a mate to their territory, why are they expending energy in defending one? The obvious answer that comes to mind is food. The theory goes that the bird is defending a territory that will be able to provide it with sufficient food to see it through the non-breeding season. It sounds entirely plausible, but unfortunately it isn’t the case.
The territory in early autumn is full of food, so you’d expect the territory holder to be more relaxed when it comes to defending it, but the opposite is true; the birds are more aggressive, constantly driving off intruders.
Then, when the weather turns colder in December, and food is harder to come by, you’d expect the territory holder to be extremely vigilant and aggressive, yet they become more relaxed, allowing intruders to feed openly within the area.
In extreme weather, several Robins can be seen feeding in the one spot. This suggests that the setting up of territory in the autumn has nothing to do with food provision.
The males of the previous breeding season’s territories tend to remain resident within them, although the boundaries may be slightly modified. The female will sometimes also defend a territory near to the breeding one, but they are more likely to move away.
In fact, the word ‘move’ doesn’t really do this justice; a better word would be migrate. We don’t tend to think of our humble Robin as a migratory bird, but in the east of its range it is a true migrant, with Scandinavian, eastern European and Russian birds all leaving their breeding areas for milder winter ones.
But there are no hard and fast rules when it comes to what the female British Robin does in the late autumn; some stay where they are, some move short distances and others migrate to Europe, going as far as southern Spain.
I live both in Britain and Extremadura in central Spain, and from the end of September onwards, the Robin population in Extremadura goes through the roof. These birds have to come from somewhere and at least some of them will be birds that bred in Britain.
The puzzling behaviour of Robins
I often wonder whether the Robins I see on my Extremadura patch in the winter are the same Robins I see on my British patch in the spring and summer! They start this southerly journey at the same time the birds that are staying behind start their autumnal song.
Those that head for some winter sun in Europe, then return to their breeding areas by the beginning of March.
It’s not that unusual for the males and females of a migratory species to winter in different areas from one another. Waders, in particular, exhibit this behaviour, with the Black-tailed Godwit being a good example, but the Robin is unusual in that it is (mainly) just one sex, the female, which migrates, while the males stay resident.
How or why this behaviour has evolved is something of a mystery. Perhaps in the past, Britain’s population of Robins was more migratory than today, and the female behaviour now is a throwback to that time, but that still doesn’t explain why just the females do it, and even then not all of them.
One thing for certain is that there will be a reason – small birds are not going to expend vast amounts of energy flying hundreds of miles on a whim. It goes to show that we have lots to learn when it comes to bird behaviour, even for our most familiar species.
The other puzzle is why the males expend lots of time and energy in establishing and defending a territory in the autumn. If it’s not for breeding purposes, or food, what is going on? There are a number of theories, but none are conclusive.
In the period just before the onset of this autumnal territorial behaviour, Robins are hard to find. We tend to think of the Robin as just being there, but if you keep notes on the birds you see in your garden or on your patch, you may well have noticed that in the second half of the summer these common little birds are not so easily seen.
Robins undergo a comprehensive moult in July, and when they do so they become far more reclusive in their behaviour. As they are vulnerable to predation while they are moulting, they spend much of their time skulking in thick cover. They even stop singing in an attempt to avoid drawing attention to themselves.
With the moult finished and the Robins resplendent in their new plumage, they emerge from the shadows and once again become the bold bird that we all know. At this time, the day length begins to noticeably shorten and the temperature can start to drop, both factors corresponding to the conditions found in spring. Is it possible that the Robin’s physiology is tricked into thinking that spring is here again?
It is a theory put forward by many, and similar behaviour is seen in other species in different parts of the world at the end of the summer, but if this is so, why is it that the Robin is virtually unique among British birds in this?
Another theory relates to the fact that the Robin is not the cute, friendly bird of Christmas card fame, but a rather aggressive species that readily enters into disputes. Could it be that after spending several weeks skulking and hiding away while it went through the moult, the Robin feels the need to reassert itself over its neighbours and the now adult-feathered first-year birds?
By singing and defending a territory, it could be re-establishing the pecking order, so to speak. I don’t know the answer, but what I do know is that I am glad they do it, as listening to the song of the Robin when the rest of the bird world seems to have fallen silent is definitely one of life’s greatest pleasures.
Why is is the Robin a Christmas card star?
One theory is that, at the time the sending of Christmas cards first became popular, in the 1860s, postmen wore bright red uniforms, and were so sometimes called ‘Robins’ – early Christmas cards include designs in which the bird bears an envelope in its bill.
But, there seems to have been an earlier association between the bird and the Christmas period, and Christianity more generally.
One fable holds that when the baby Jesus was in his manger, the fire lit to keep him warm blazed up very strongly. A brown bird placed himself between the fire and Jesus, fluffed out his feathers, but got its breast scorched by the fire, and the Robin was the result.
Another story is that a Robin pulled a thorn from the crown of Christ while he was on the cross, and that it was Christ’s blood that created the bird’s red breast.
Robins also crop up in the stories of several early British saints, such as St Mungo (also known as Kentigern), who is said to have restored one to life, so the religious links extend back into the early medieval period and perhaps beyond.
But maybe the reason is much simpler. Their red breasts mean Robins are noticeably colourful at the darkest, dullest time of year, and their habit of singing throughout autumn and winter embeds them in our consciousness just as the festive season approaches – perhaps the cards are our nod to their role in lifting our spirits when we need it most.
Scientific name: Erithacus rubecula
UK numbers: 6.7 million territories
Habitat: Woodland, hedgerows, parks
Diet: Insects, worms, fruit and seeds
By Dominic Couzens
It was a bitter late autumn day with a gale blowing so hard that any words you tried to speak were whisked unceremoniously from your lips and deposited as junk in the outbox of the airwaves. I caught myself murmuring: “There shouldn’t be a Kingfisher here.”
At this moment, the Kingfisher concerned would probably have echoed the sentiments. It was perched on what looked like a tin can, beside the meandering creek of an estuary at low tide. It was hunkered at the bottom of a mini-downland of raised mud just above the water level, doing its best to find shelter.
Its neighbours were Redshanks, similarly huddled and hunkered under the brow of mud. They should have been feeding on the super-fertile shallows along the creek, but, in the howling westerly, they risked being blown off their feet.
Their bejewelled neighbour risked being blown to oblivion. The wind ruffled contemptuously at the gorgeous plumage, still colourful through a rain-lashed telescope lens. The dandy looked incongruous here, like a glamorously dressed woman disgorged from a nightclub in a freezing dawn.
The last time I had seen a Kingfisher looking so out of place was many years ago, when I was birding in the middle of an oak woodland. It was one of those days when all the trees seem bored of summer, the spring green long faded and the hum of activity hushed.
There came the loud, whistling call and the familiar cerulean flash of diminutive Kingfisher-dom, blue out of the blue. There was no stream through this wood, nor any water within a 20 minute walk. Yet, there was no doubt about the bird’s identity, only incredulity in its wake. These observations, taken in isolation, would prove nothing about Kingfishers except that, in common with any bird species, they can surprise us. However, the truth is that neither observation would even raise the eyebrows of a Kingfisher expert.
To us, an estuarine Kingfisher might seem out of place, but it is our expectations that are wrong. Kingfishers are routinely found on estuaries. And Kingfishers also wander during the late summer, when they can turn up in the middle of woods and other peculiar places.
Kingfishers suffer from Breeding Bird Syndrome, when our perceptions of a species are wrapped up almost entirely in their summer programme. The same applies to Swifts, which probably spend far more of their lives flying over Giraffes than they do over English cricket pitches, and Puffins, which spend the smallest fraction of their lives carrying sand-eels in their bills, while endless days they are floating in the open ocean. We expect to see Kingfishers by glinting rivers, on a lazy bend with luxuriant growth and dancing mayflies, not on a windswept estuary.
Kingfisher life in the 'off-season'
None of this takes into account a Kingfisher’s life in the off-season, when everything from the weather to the social climate is different and unsettled. For one thing, all the youngsters have been booted out of their parents’ territories and are on the look-out for a place that they can defend for their own.
At the same time, adults evacuate from territories that cannot sustain them in the winter months, such as small brooks in the uplands. A few individuals might even enter the country from abroad. All are seeking the nirvana of a smooth, slow-flowing stretch of river where the water is shallow and productive.
Demand outstrips supply, the best areas are quickly bagged and there is an almighty halcyon reshuffle. Displaced birds fly hither and thither, some just a short distance, some for much longer distances (250km has been recorded). Some individuals find themselves in what might almost be termed experimental territories. They try out fishing in garden ponds; birds plant themselves in brooks in the middle of woods; and a good many are forced into salt water, to estuaries, harbours, even to rocky shorelines, where they fish the rockpools like human toddlers.
These places seem to be a far cry from the ideal, but it is not as though these birds are landing on Mars. Kingfishers eat fish, and their skills are fully translatable from fresh to salt water. British Kingfishers are actually quite one-dimensional in their feeding behaviour – it is ‘dive into water to snap up fish’ or nothing (one exhaustive study on nearly 17,000 prey items found that only 0.07% were non-piscivorous.) The birds are perfectly capable of diving after a brief hover, or even plunging in straight from horizontal flight, but their method is really very simple. Would they need to adapt much to the supposedly sub-optimal habitat of salty or brackish water?
The real question is, perhaps, why don’t we see many Kingfishers on our estuaries and coasts? There are plenty of fish in the sea. If you look at the Kingfisher family as a whole, quite a number of species are coastal specialists, and a few are routinely seen by the beach – I watched a Pied Kingfisher accompanying gulls and terns on a beach off southern Israel just recently.
The same species has been recorded three kilometres out to sea. Even our own species of Kingfisher may show different behaviour abroad, where it occurs east to Japan; it often occurs in mangroves, for example.
Presumably something isn’t quite right, because otherwise we would all see these birds more frequently on our visits to coasts. Perhaps there isn’t enough shelter, or there is too much disturbance from other bird species?
Perhaps the fish themselves stay deeper in the water and are more difficult to catch. There are certainly many more foragers on estuaries than along rivers. But, for the moment, we can still be surprised to see these gaudy birds there.
Kingfisher quirky behaviour
A couple of recent studies have unveiled another interesting quirk of Kingfisher non-breeding behaviour, one that I haven’t ever witnessed myself. It throws a harsh light on the difficulties young birds face when they initially leave their birthplaces, and suggests a novel way of dealing with it. It seems that, on occasion at least, siblings settle in a new place together and look out for each other.
On a river in Poland (ie central Europe), the observers found that, while adult Kingfishers always dispersed singly to their winter territory, in four out of 24 cases, juveniles came in twos.
Under the pressure of competition from other birds using the river, youngsters were often displaced from the first few territories into which they had settled, only remaining for a short time.
However, when the birds arrived as pairs, they occupied the best territories and remained for a much longer period of the non-breeding season. Working co-operatively, birds making up these pairs were able to fight off the competition for longer. It is believed that such pairs are probably from the same family.
In the Kingfisher family, blood relatives often occur in permanent groups (kookaburras, for example), so perhaps European Kingfishers are exhibiting a family trait. The makeup of these pairs (and occasional small groups) is still not fully understood, though, so it could be a fascinating area of study.
For now, though, we can all contemplate an even stranger sight than a Kingfisher cowering in the bowels of a bitter winter estuary – two Kingfishers cowering together.
Scientific name: Alcedo atthis
UK numbers: 3,800-4,600 breeding pairs
Habitat: Alongside still or slow-flowing water
Diet: Fish and aquatic insects
By Ian Parsons
The Long-tailed Tit is not a typical tit, in fact it isn’t actually a tit at all! It turns out that the long-tailed visitor to your bird feeders is actually more closely related to the babblers of India and South-east Asia than it is to the Blue Tits and Great Tits that we associate it with. But the long tail is longer than the rest of the body, so other than not being closely related to the true tits, the Long-tailed Tit is a very well-named bird indeed!
They are also on the increase, which is an unusual thing in British birds and one that is definitely worth celebrating, especially as a main part of their preferred habitat is towns and cities – meaning that these delightful little birds are an increasingly common sight for many of us.
Feeding the birds in your garden is a great way to see lots of species close up, it is a rewarding experience for us and one that many people are rightly enthusiastic about. It is also very important for many bird species, with the Long-tailed Tit being a great example: the reason that this bird is doing so well in the urban and semi-urban habitats of our towns and cities is because of us feeding the birds in our gardens.
But, just because the Long-tailed Tit is doing well doesn’t mean that life is easy for it. The population in the UK is extremely vulnerable to the weather, with very cold winters resulting in large drops in numbers the following year.
But it isn’t just the winter weather that can cause problems for the bird, the weather in spring and autumn is also strongly linked to the bird’s survival, with studies showing that warm weather in both seasons has a positive effect on numbers, whereas wet springs and cold autumns have a negative effect on numbers.
However, Long-tailed Tits are able to bounce back relatively quickly from periods of bad weather thanks to their potential breeding output. The result is large fluctuations in their overall numbers year on year; thankfully though, the trend is an upward one at the moment.
The winter is the time that Long-tailed Tits are at their most obvious. They form loose flocks ranging from five to 30 birds (even up to 50!) that rove the local area looking for feeding opportunities. Sometimes these flocks intermingle with other small birds, while at other times they are purely Long-tails!
Being in the middle of one of these feeding parties is always a delight. Their soft, bubbly contact calls fill the air and you find yourself surrounded by these great little birds, hanging off the branches above your head or flitting past your face as they move from tree to tree, seemingly oblivious to your presence.
Birds form flocks for many reasons. For example, the more eyes there are, the better the chance a predator will be spotted early enough for the flock to take avoiding action. More birds can also mean more chance of finding food (although it then has to be shared!), but it seems as if Long-tailed Tits form their flocks for another reason. They form them to keep warm.
While, undoubtedly, the birds get other benefits from grouping together, it seems that a major reason behind this behaviour is to help the birds get through the long, cold winter nights.
The threat of winter for Long-tailed Tit
Long-tailed Tits are tiny birds. Their long tail makes them look bigger than they are, but the reality is they are very small. Small bodies lose warmth far more quickly than larger ones and, therefore, Long-tailed Tits are prone to hypothermia during the chilly nights of winter.
To combat this, the group of Long-tailed Tits get very busy as dusk approaches, feeding up before selecting a nice thick shrub or tree to roost in. Within the confines of the branches the birds huddle together. By getting up close and personal with the other members of the flock, who are often related, they minimise the amount of heat that they lose. It is a brilliant and sociable adaptation.
Come the spring, with its warmer nights, the flocks disperse and the birds pair up to breed. The breeding season starts early for these little birds, often in February, but the reason for the early start has nothing to do with maximising the broods it can produce in the one year – it is all about their fabulous nest, an avian architectural wonder.
The nests are basically a large pouch with a small entrance hole towards the top, constructed by both the male and female. They can take up to three weeks to make. They are made by using moss, lichen, feathers and spider silk, which the birds gather from the silk egg cocoons of various spider species. There are around 6,000 individual components used to make these wonderful structures. The spider silk is the glue holding together the moss, lichen and feathers, but it is even cleverer than that.
A study of the construction of the nests revealed that the spider silk is used to form small loops that snare the tiny, hook-like leaves of the moss, creating a strong bond that prevents the nest falling apart, even when it is full of youngsters. You have to wonder if the person who invented Velcro ever watched Long-tailed Tits make a nest...
Once the nest is constructed, the birds then need to line it, and this itself is a mighty task. The tits line it with soft downy feathers, but they don’t just use one or two, they use about 2,000! It is amazing to think that they are able to find that many downy feathers, but find them they do, and the nest must be really comfortable as a result.
I remember, many years ago, approaching a Goshawk nest site early in the season to check occupancy (under licence of course). On my way in to the site, I passed the raptors’ main plucking post (always a great thing to check out!) and, as I did, I flushed up a Long-tailed Tit.
At the time, it didn’t register with me what this bird was doing, but as I think about it now it makes sense. A plucking post is going to be a great source of downy feathers. Nothing is wasted in nature.
Despite the care and attention that goes into building the nest, many actually fail. When this happens, the adults involved sometimes help out with a nearby nest, helping to provide the young with food and to keep predators away.
The birds that do this are often related to the birds that they are helping, so they benefit by ensuring the future of related offspring. It is also thought that they gain experience, which may mean that the following year they are less likely to suffer a nest failure again.
One thing is for certain, this behaviour greatly benefits the young in the nest. Studies have shown that they have much greater survivability if their parents have been helped out in rearing and defending them. The Long-tailed Tit is a social bird. Whether they are helping a relation rear their young or snuggling up to them in the depths of winter to keep warm, these are birds that look out for each other.
Where to see Long-tailed Tits
You can see these little birds pretty much anywhere, except for the far north and west of Scotland. Look (and listen) for them in woodland, farmland hedgerows, scrubland, parkland and also in your garden – check your feeders!
They will form a flock with other tit species during the winter months.
Alternative names for Long-tailed Tit
Old English names for the Long-tailed Tit include: Long-tailed Pie, Mumruffin, Bottle Tit, Bum Barrel, Bum Towel, Oven Bird, Bag and Hedge Jug to name a few!
Long-tailed Tit fact-file
Scientific Name: Aegithalos caudatus
Length: 13-15cm (8cm of which is the tail!)
UK numbers: 340,000 UK breeding territories
Habitat: Towns and cities
Diet: Mostly insects, occasionally seeds in autumn.
By Dominic Couzens
Whatever you have learnt about ducks probably isn’t true about the Goosander. This is a very different animal from your quacking park staples, and almost everything they do, it doesn’t do.
If you take a list of unusual duck facts, many of them will be true of Goosanders. The Goosander is a duck apart, a thoroughbred and a maverick. Far from being a portly, bread-ivorous consumer of benefit handouts, the Goosander is
a big-game fishing duck.
Instead of occupying slummy waters in the urban sprawl, this bird is at home in fast-flowing, highly oxygenated, supercharged wild rivers and deep pools. It lives, in many parts of its range, among forests full of bears and wolves. It is the antithesis of the duck that is, if not domesticated, then domiciled. It is wild and untamed.
My first experiences with these characters always led me to assume that people, in the view of Goosanders, were to be avoided. From deep reservoirs in winter to streams in summer, you tended to see the back end before you saw the front, the big, torpedo-shaped bodies whistling off and away, not a thought for pleasantries. There is no breaking bread with a Goosander.
Their diet, too, is the opposite of a handout. Many species of ducks, throughout the world, take an extremely leisurely approach to feeding. Mallards, for all their adaptability, give the impression that they are never making any more effort than we would to dig up carrots. Shovelers bulldoze the water surface, Teals pick seeds from the mud; Pochards graze underwater and sleep for much of the rest of the time; even Eiders in the sea only dive down to yank immotile cockles from the sea bed.
Goosanders, though, are birds that chase, and their prey is both fast and reluctant to be caught. They are among the very few ducks that catch fish for a living, along with their ‘sawbill’ relatives, the Red-breasted Merganser and Smew. These ducks need pace underwater, and they need unobstructed space in which to spot and snatch their prey.
Almost any fish species less than 20cm in girth may be consumed, anything from a stickleback to a salmon. They catch what is most abundant; in extreme cases they can swallow a fish 36cm long. They will search among the sediment and among stones, in a submarine world it is hard for us to imagine. They have excellent vision and will hunt well into dusk, or even after dark.
The serrated edges of their mandibles allow them to hold slippery prey.
Goosander: Hunting and homes
Where fishing is good, Goosanders will gather. In contrast to the quarrelling Mallards spitting over bread, these sleek hunters will hunt co-operatively, and with deadly effectiveness. Sometimes they dive as one to startle fish into rash decisions, and sometimes they will form a line to drive shoals of prey into shallow water. There is no jostling in this classy species.
Goosanders don’t follow the duck trail in much of their breeding behaviour, either. Despite being large, they nest in holes in trees, or sometimes rocks or strange sites, such as hollow logs on the ground, or in buildings.
These holes may be anything from 1m above ground to an impressive, decidedly lofty 30m. True, that epitome of duck-hood, the Mallard, will sometimes nest in tree-holes as well, but among duck species as a whole it remains unusual. Most types, from Tufted Ducks to Gadwalls, nest among vegetation on the ground.
One might immediately sense a problem for Goosanders, when looking for nest-sites: where can they find anywhere big enough? You could fit a Mandarin or a Smew into a small space, but not a Goosander. The penthouse suite must be spacious. Fortunately, in most parts of their range, Goosanders can call in large woodpeckers to provide housing.
In Europe, it is Black Woodpeckers and in North America, Pileated Woodpeckers, both of which are impressively bulky, and the woodpeckers’ habit of continuously excavating holes means that the ducks can keep their numbers up.
In Britain, where Black Woodpeckers are absent, Goosanders can use other holes and hollows, perhaps where branches have broken off. They will also use nest-boxes.
Almost all duck species’ progeny are quickly led to water almost as soon as they hatch. Nestling Goosanders spend their first day or two in the hole and then conform to type.
Of course, this arrangement comes with a snag, if you are 30m above ground. The chicks might be lightweights, physically, but they certainly aren’t in courage; necessity urges them to make the jump to ground, and then the mother urges them on, during the walk to water, however far that might be – 1.5km has been recorded.
It is quite a jolting start in life. In their early days, the mother may treat the chicks to a parental quirk which is unusual among wildfowl, a ride on her back. Presumably this has some survival value, but she isn’t always able to accommodate the whole brood, which can number 12, and occasionally as much as 17.
Goosander mystery solved
Looking at the Goosander’s overall behaviour, it seems to follow almost every unusual lead in the world of wildfowl, from hole nesting to ferrying young to chivvying fish.
Yet another strange behaviour that it exhibits might qualify as the strangest of all, and it is taking place at about the time you are reading this article, or just after.
You are probably aware that some birds perform special migratory movements for the purposes of moult. The most famous of these birds is the Shelduck, which flies from Britain to Germany in the summer, while Barnacle Geese sometimes fly north of the breeding grounds to moult. They go for no other reason than to change their feathers in a safe environment.
It has been discovered quite recently that Goosanders also have a moult migration, yet extraordinarily, it is confined to the males. For many years, it had been noted that the drakes were absent from their Scottish rivers from June to October or so, even where the mothers and broods were feeding, and for many years their whereabouts was a mystery.
It has now been shown that these drakes undertake a remarkable journey, travelling all the way to the North Cape of Norway. Here they mingle with 35,000 other males from other parts of western Europe and loaf about, moulting their plumage.
It is well known that ducks commonly show differential migration, with each gender exhibiting a different migratory strategy – for example
male Smews remain close to the breeding grounds in winter, while in Britain, further away, we see more females and immature males.
However, for the male Goosanders to migrate such a significant distance, leaving the females behind, is of a different order of magnitude.
On the other hand, for such a remarkable, unconventional duck, it is just another example of doing everything in its own way.
Scientific name: Mergus merganser
UK numbers: 3,100-3,800 breeding pairs /
12,000 wintering birds
Habitat: Upland rivers in summer, lakes, gravel pits and reservoirs in winter
Pic: Colin Varndell / Alamy Stock Photo
Words: Kate Risely, of the British Trust for Ornithology (BTO)
The call of a Water Rail is extremely un-bird-like, and never fails to take me by surprise! They produce a wide range of loud squealing and snorting noises, traditionally known as ‘sharming’, which brings to mind an alarmed piglet.
The birds themselves are extremely hard to see, preferring to stay hidden in thick vegetation. If you are lucky enough to get a good view, adults of this species can be recognised by the long, red bill, black and white barring on the flanks and tiny, cocked tail.
They are also surprisingly small, half the weight of a Moorhen, and very narrow-bodied. It’s worth learning the differences between Water Rails, particularly juveniles, and the other, rarer Rallidae – Spotted Crake, Little Crake and Baillon’s Crake – as views are often fleeting.
In winter, we are joined by migrant Water Rails from Scandinavia, northern Europe and even further afield; a wintering adult ringed in 1990 in Lancashire was found the following breeding season nearly 2,000 miles away in Belarus, unfortunately killed by a cat.
It seems incredible that such skulking birds can fly long distances out in the open, and in fact they are very rarely seen on migration as they are night travellers, flying under cover of darkness, and are normally safely hidden by daybreak.
Winter is the best time to see Water Rails, partly due to the larger number around, and also because birds are sometimes forced to forage in the open when the water surface is frozen solid. The BirdTrack reporting rate shows that birdwatchers are most likely to record Water Rails in November and December.
Their preferred breeding habitat is static or slow-flowing fresh water with very thick vegetation and preferably some open mud. The Bird Atlas 2007–11 distribution map shows that breeding Water Rails are patchily distributed throughout the lowlands of Britain and Ireland, with strongholds in Ireland, East Anglia and southern Scotland.
Since the first breeding atlas in 1968–72 they appear to have been lost from many breeding sites in England and Ireland, but increased in Scotland – however, these results should be interpreted with considerable caution, due to the difficulty of detecting this species on general surveys.
National population estimates for all of our breeding and wintering birds were published in 2013, including an estimate of 1,100 Water Rail territories. This figure was calculated using reports to the Rare Breeding Birds Panel, though it was flagged at the time as ‘a contender for the least reliable population estimate’!
This number was challenged by those with experience surveying Water Rails using tape playback to encourage the birds to call, who maintain that breeding Water Rails are extremely under-recorded through standard survey methods.
Playback surveys have resulted in an estimate of 800 territories in Scotland alone, and it has been suggested that the overall UK population might be in the order of 4,000 to 6,000 territories. Such wildly disparate population estimates, and the uncertainty over whether the species is increasing or declining, highlight the problems with understanding and therefore conserving such elusive birds.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
A nestbox seems to be the essential garden accessory – every suburban garden has to have at least one, and they are also common in urban areas.
There are nearly five million nestboxes in gardens across the UK, but these are mainly used by just two species – Blue Tit and Great Tit. Of these, Blue Tit is slightly more common, so can probably lay claim to the title of the greatest user of nestboxes in the UK.This fact makes me think; where would Blue Tits be without people?
It’s not just about nestboxes – Blue Tits are one of the main beneficiaries of the bird food that so many of us provide in our gardens. Although the habit of putting out crumbs and scraps for birds was widespread in Victorian times, it was during the post-war period that the practice of feeding garden birds really took off.
At that time, the items most commonly provided were monkey-nuts threaded on strings, and coconut shells filled with suet – hanging foods designed specifically to appeal to the agile and generalist Blue and Great Tits.
A look at the bird population trends generated from the Common Birds Census and the more recent Breeding Bird Survey shows that Blue Tits have experienced an upward population trend since the 1960s, probably as a direct result of people providing bird food and nestboxes that disproportionately benefit this species.
The huge rise in garden bird feeding, and the habit of providing nestboxes, came at a time when the proportion of the human population living in towns and cities was increasing rapidly, and it’s thought that feeding birds was related to the desire of town-dwellers to re-establish contact with the natural world.
And what more enjoyable sight than a Blue Tit outside the window? We are lucky, indeed, that this bold, opportunistic species, so quick to exploit garden bird feeders, also happens to be so pleasing to the eye.
An interesting fact about Blue Tits is that although the males and females look alike to us, the birds themselves can tell the difference – all birds can see ultra violet light, and the plumage of male Blue Tits reflects UV light more brightly than that of the females. No matter how attractive their colours, however, familiarity certainly breeds contempt, and the Blue Tit is an under-rated bird – if they were rare, they would be at the top of every birder’s must-see list!
Interestingly, the population trend graph for Blue Tit has dipped in recent years, and results from Garden BirdWatch have suggested that the number of Blue Tits using gardens has started to decline – this could be due to a change in the kinds of bird food provided, with seed feeders replacing peanuts and fat balls, which may mean that finches such as Greenfinch and Goldfinch are out-competing Blue Tits at garden feeding stations.
This small decline notwithstanding, Blue Tit is still one of our most common garden inhabitants, and if you have a nestbox in your garden, there’s a good chance that Blue Tits will make use of it. If you have birds nesting in your box, you can report this fact to the BTO’s Nest Box Challenge in the spring.
However, you may be surprised to hear that birds don’t just use nestboxes for nesting – many birds will roost in cavities overnight during cold winter weather. We currently very know little about how important nestboxes are for this purpose, so the BTO is running a Roosting Survey until the end of February 2011 – why not take a look at what birds are roosting in your garden nestbox? We hope that your observations will add to our understanding of how birds such as the Blue Tit have benefited from garden habitats.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
There can be no mistaking the sound of a Cetti’s Warbler. These birds reveal their presence by their explosive song, but are seldom seen, preferring to skulk close to the ground in their reedbed or wet scrub habitats.
This species is now widespread across the south and east of England, following a substantial population expansion. The 1968-72 Breeding Atlas showed that Cetti’s Warblers were confirmed breeding in just three 10km squares, on the north Kent coast – and were only recorded as present in two other 10km squares in the whole country!
By the time the 1988-91 Breeding Atlas was published, they had been confirmed breeding across Hampshire and Dorset, with scattered breeding records in the south-west, Pembrokeshire and East Anglia (but had been lost from north Kent).
We are still in the process of collecting records for the 2007-11 Atlas, but BirdTrack results for 2009 reveal that Cetti’s Warblers are now widely recorded around the coasts of East Anglia, Kent, Sussex and Hampshire, with many inland records as well. This population expansion could be partly explained by the run of mild winters up to 2008 – Cetti’s are one of our few resident warblers, and they feed on aquatic insects during the winter, so prolonged freezing conditions can severely affect the population.
Cetti’s Warblers are not yet numerous enough to be monitored by the Breeding Bird Survey – we can only calculate reliable population trends for species that are found on over 40 BBS squares per year. In 1994, the first year of the BBS, Cetti’s Warblers were found on only two BBS squares, out of 1,500 surveyed.
Ten years later, in 2004, Cetti’s were recorded on 14 squares out of 2,500, and by 2008 their occurrence had risen to 38 squares out of 3,200 – nearly at the threshold figure. While we can’t yet monitor the population changes of this species by surveying randomly-located sites, we have another monitoring scheme that is well suited to the job.
The Constant Effort Sites (CES) ringing scheme is a way of monitoring bird numbers and productivity through standardised trapping of birds. Ringers make twelve visits to a site during the spring and summer, and set the same number of mist nets in the same locations on roughly the same dates, allowing annual changes in bird numbers to be calculated.
Since ringers record whether birds are adults or juveniles, we can also use CES data to record the ratio of juveniles to adults each year, and hence the productivity of the population. Constant Effort sites are often located in the reedbed or scrub habitats favoured by Cetti’s Warblers, and the results show that numbers of this species have increased on Constant Effort sites by over 250% since 1997.
Here at the BTO headquarters we have observed this expansion first hand, on our small nature reserve (the BTO, as a research organisation, does not buy or manage nature reserves, but we were lucky enough to gain one along with our Norfolk headquarters). The Nunnery Lakes reserve has a reedbed and scrub area, on which BTO staff run a Constant Effort ringing site during the breeding season.
A single Cetti’s was heard singing in our pocket-handkerchief sized reedbed last year – we hoped it would attract a mate, but our hopes were not high, as this species is still uncommon in the Brecks. We were therefore surprised and pleased when, during our CES ringing, we caught not only the male, but also a female, together with three recently-fledged youngsters! Proof indeed of the expansion of the breeding range, and another ‘confirmed breeding’ dot for the Atlas map.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
Even though our summer migrants are long gone, and the days are drawing in, I think the first real sign that winter is on the way is the sight, and sound, of winter thrushes.
Fieldfares are the northern equivalent of Mistle Thrushes – of similar size and posture, and with the same white underwing coverts – but far more striking in overall appearance, with a dark eye patch, grey head and rump, chestnut mantle, and handsome stripes and streaks on a deep orange breast.
Fieldfares are absent from the UK during the breeding season, apart from a handful of pairs that breed in Scotland, but flood into the country in autumn – the BirdTrack reporting-rate graphs show numbers rising very sharply from zero in early September to a peak in early October.
Fieldfares are social birds, and, unusually among thrushes, they often nest in loose colonies. The groups are fierce in defence of their nest sites, and have been known to bombard would-be nest predators with their faeces.
In winter, they are no less gregarious, and are almost always found in flocks, often associating with Redwings. These flocks are highly nomadic, and analysis of records submitted to the 1986 Atlas of Wintering Birds showed that the distribution of Fieldfares was related to weather conditions – in the cold winter of 1981/82 there was a noticeable shift of the Fieldfare population to the south of Britain, and in all three winters a comparison of the early-winter and the late-winter maps showed a southward movement during the course of the winter.
Birds ringed in the UK have been recovered as far afield as Portugal and the Balkans in subsequent winters, highlighting the transient behaviour of the wintering population. It is this transience that makes a census of winter bird populations such a tricky affair.
In the breeding season, birds are tied to a nest site for the duration of the season, and are often evenly spread out throughout their breeding range, so they are relatively straightforward to monitor by standardised surveys such as the Breeding Bird Survey. In the winter, results are harder to interpret, which is why detailed information collected during this forthcoming winter, the last winter of fieldwork for the 2007-11 Bird Atlas, will be so important.
We often think of Fieldfares as being birds of the open countryside, and, unsurprisingly, their name means ‘the traveller through the fields’ in Anglo Saxon (talking of names, their Latin name, Turdus pilaris, rather strangely translates as ‘the hairy thrush’, apparently due to a misreading of the Greek trikhas, meaning thrush, for trikhos, meaning hair!).
During hard weather, they are unable to access the soil-dwelling invertebrates on which they normally feed, and move in to orchards, where they have been known to congregate in huge numbers, and into gardens, where they feed on windfall fruit and berries.
They are even recorded by the BTO’s Garden BirdWatch – during the cold winter of 2009/10, Fieldfares were recorded in nearly a third of the 14,000 Garden BirdWatch gardens, a three-fold increase on the normal numbers.
I must confess to being very envious of people with gardens rich enough to attract Fieldfares – but I will be content to go out and find them for myself, in a wintry farmland landscape. After all, if all the birds came to me, where would be the incentive to go and do my winter Atlas surveys?
Words: Kate Risely, of the British Trust for Ornithology (BTO)
The tiny, jewel-like Goldcrest is a bird whose fortunes I have been following with interest. One of our smallest species (Firecrest is of very similar stature), weighing just 6g, and a year-round resident, Goldcrest populations can crash after hard winters – of which we have had a few in recent years. The winter of 2008/09 was the coldest for 10 years, with particularly cold spells during December and early February.
Numbers of Goldcrests reported to BirdTrack were noticeably lower at the start of 2009 than in the previous two years, leading us to believe that the results from the 2009 Breeding Bird Survey (BBS) would show a marked drop in numbers – and so it proved.
Goldcrest populations had been climbing since the start of the BBS in 1994, possibly due to a run of mild winters, and by 2008 numbers of this tiny bird had reached their highest levels since 1994. However, the 2009 BBS results revealed that the breeding season Goldcrest population fell by more than half between 2008 and 2009, very probably due to mortality during the winter months.
If we look further back into the BTO’s records, we see that Goldcrest populations have experienced similar fluctuations in the past. Numbers were very low following the winter of 1962/63, climbed to a peak in the early 1970s, and crashed again, before showing smaller fluctuations up until the 1990s, when numbers began to rise steadily.
The large year-to-year changes, with numbers bouncing back after crashes, reflect the high breeding potential of this species. Goldcrests, which generally nest in conifers, can lay up to 12 eggs in a clutch (though 6-8 is more common).
These eggs, though barely larger than peas, can represent one and a half times the bodyweight of the female – a huge reproductive effort. Remarkably for such a small bird, Goldcrests breed right up to northern Scandinavia – although their chances of winter survival are even lower in the far north, and many Scandinavian birds migrate to the UK in the autumn.
The fact that such diminutive birds can survive a gruelling sea crossing is amazing, and in the past people simply did not believe that these birds could migrate at all. Observations of Goldcrests arriving on the UK’s eastern shores in the company of larger migrants led to the somewhat far-fetched belief that they hitched a lift in the feathers of Woodcocks or Short-eared Owls.
Looking at the BirdTrack reporting rates for 2009, it is clear that, as well as numbers of breeding birds being lower than previous years, the influx of birds from Scandinavia in the autumn was also far smaller than usual. One explanation for this could be that Scandinavian breeders were also hit by the hard winter of 2008/09, resulting in smaller numbers migrating in the autumn.
After the poor year of 2009, Goldcrest populations would normally be expected to bounce back. However, the winter of 2009/10 was even more severe than the previous year – the average temperature for the period December 2009 to February 2010 was 2°C below the long-term average, making it the coldest winter since the 1970s! We don’t yet have the BBS results from 2010 to show us how this winter affected Goldcrest breeding numbers, but indications from BirdTrack seem to show that numbers during the breeding season were roughly similar to 2009.
By the time you read this, Goldcrests should be flooding into the country, filling the coastal scrub in places like Norfolk, Lincolnshire and Northumberland, and no doubt closely scrutinised by those hoping to find a rarity amongst them.
It will be interesting to see the shape of the BirdTrack reporting rate graph for winter 2010 – will there be the normal peak in October? Or will the 2009 pattern, where numbers hardly rose at all, be repeated? And for the sake of the birds, I hope that this coming winter is less severe than the last two.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
I was surprised to find out just how rare Great Crested Grebes once were – I wonder how many people know that in 1860 there were only around 50 pairs breeding in the UK?
In modern times we tend to look to habitat degradation, or climate effects, to explain declines in bird numbers, but back then human effects on bird populations could be much more direct. Great Crested Grebes were slaughtered on an industrial scale in the latter half of the nineteenth century, to feed the demands of fashion.
The fine chestnut head plumes were used to decorate hats and other accessories, and their densely feathered skins were used in the clothing industry as ‘grebe fur’. The eggs were also taken, as food and for sale to collectors.
Fortunately, and partly as a result of these kind of devastating declines, this period saw the birth of the modern conservation movement, and laws were passed to safeguard waterbird populations from hunting.
By the 1930s, seventy years later, wild birds were no longer generally seen as resources to be exploited, and the days of mass-participation volunteer bird surveys had arrived.
The Great Crested Grebe Enquiry in 1931 was one of the earliest national censuses of a single species, promoted in The Times, and attracting more than a thousand volunteer surveyors. Around a thousand water bodies were covered, and the results of the Enquiry, published in British Birds, concluded that the breeding population of Great Crested Grebes in England, Scotland and Wales was around 1,200 pairs.
The paperwork from the 1931 survey is preserved in the BTO archives, together with records from subsequent surveys in 1946, 1965 and 1975, the results of which were published in the BTO journal Bird Study.
By 1975 there were thought to be around 3,500 pairs, an increase that can be attributed to the cessation of persecution, and a huge increase in the numbers of flooded gravel pits due to the demands of the construction industry. Great Crested Grebe populations are now monitored via the annual Breeding Bird Survey, which shows that numbers are still increasing – by 28% since the start of the survey in 1994, and by 8% just between 2007 and 2008.
There are now thought to be around 12,000 pairs breeding in the UK, and this population estimate will be updated when the BTO’s forthcoming Bird Atlas 2007-11 is published. Any records of Great Crested Grebes would be of use to the Atlas, particularly those where the birds can be confirmed as breeding – which, for this species, can be very easy!
Pairs of Great Crested Grebes perform elaborate courtship displays, shaking their heads, dipping their necks, and rising out of the water with beakfuls of weed in the famous ‘weed dance’.
The nests are obvious platforms of weed, and when the chicks have hatched they can be seen riding around on the backs of the parents, with tiny black-and-white striped heads peering out between the feathers (I’ve yet to meet anybody who doesn’t go ‘ahhh’ when they see this). Interestingly, the parent birds can sometimes be seen feeding feathers to their young at this stage – this is thought to help them form pellets so they can regurgitate indigestible food items.
As familiar as they are today, it should be remembered that Great Crested Grebes are, in some senses, a conservation success story – and I’m sure that when the time comes for the next BTO Great Crested Grebe Enquiry, we will have no shortage of volunteers.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
A Hobby is always an exciting sight – hunting low over a pond or reedbed, or as a Swift-like silhouette high overhead. Seeing just one is enough to make my day, so I was amazed to hear of 61 birds seen together at Lakenheath in May this year.
Hobbies are known to congregate at good feeding sites when they first arrive back in the UK, before dispersing to their breeding grounds, but I doubt that many people are lucky enough to see so many together.
The breeding Hobby population in the UK is mostly restricted to England, though the range is expanding as the population increases. In the 1950s, the UK population was estimated to be around 100 pairs, mainly on southern heathland and downland, and the 1968-1972 Breeding Atlas showed that these birds were restricted to western parts of southern England at that time.
Since then, Hobbies have spread northwards, possibly due to changes in dragonfly and beetle populations, their main food supply. They are also increasingly found in farmland, seemingly less dependent on their traditional heathland habitats.
By the time the 1988-91 Breeding Atlas was published, Hobbies were breeding across much of England, having colonised eastern areas, and spread north to the Humber.
Today, maps of Hobby sightings submitted to BirdTrack look similar to the 1988-91 distribution map, but for the best current information we will have to wait until the 2007-11 Bird Atlas is completed. It appears, however, that Hobby numbers are increasing, even if their distribution is not changing significantly – the latest results from the Breeding Bird Survey show that Hobbies have increased by 23% since the start of the survey in 1994.
The last population estimate, in 2001, put the population size at 2,200 pairs, but numbers are now almost certainly higher than that.
Since their diet consists primarily of insects, Hobbies spend the winter in Africa, unlike any other British falcon, but in common with the European species Lesser Kestrel, Red-footed Falcon and Eleonora’s Falcon.
It is interesting that their populations are increasing, unlike so many of our other sub-Saharan migrants, which are showing severe declines. It would appear that Hobbies, as birds of prey, have not encountered the same problems on migration and on their wintering grounds as our migrant songbirds.
It is not known exactly where British Hobbies spend the winter, as there have never been any ringing recoveries south of Spain – and no Hobbies ringed anywhere in Europe have been recovered south of the Sahara. Most ringed Hobbies recovered in Europe on migration appear to have been heading in a south-westerly direction, towards West Africa, but the main wintering area for this species is believed to be the Zambezi basin.
On their breeding grounds in the UK, Hobbies generally lay their eggs in June, meaning that the chicks hatch in July, and, all being well, fledge in August. Since this species is secretive when breeding, one of the easiest ways to confirm breeding is to watch and listen for groups of newly-fledged young, sitting together on branches near the nest site.
All breeding records will be useful for the 2007-11 Bird Atlas, particularly in order to detect any expansion of the breeding range. I’ll be keeping an eye out for recently fledged young in Thetford Forest – and I’m also planning to visit Lakenheath in May next year!
Words: Kate Risely, of the British Trust for Ornithology (BTO)
Lesser Whitethroats are just that little bit different. Whilst most other British warblers migrate south at the end of the breeding season, Lesser Whitethroats head for northern Italy. Having fattened up, they cross the Mediterranean, on their way to Sudan, Ethiopia and neighbouring countries, where they exchange the thick, leafy hedges and thickets of England for thorny scrub.
Birds we see arriving in spring will have passed north through countries such as Israel and Turkey, before heading west. This all means that the Lesser Whitethroat you hear in an English lane next week may be the same bird that you saw in Crete last autumn or in Eilat in February.
The Lesser Whitethroat is one of the last of our migrants to return, arriving at the same sort of time as Turtle Dove and Swift, just before the tardy Spotted Flycatcher and five weeks after the early birds.
It is not easy to get a good view of a Lesser Whitethroat and to see the striking mask, set off by an ash-grey cap and a white moustachial line. Unlike the ebullient male Whitethroat, perfectly prepared to shout from the top of a hawthorn hedge or take to the air in a song-flight, his smaller cousin prefers to stay in the middle of a bush to deliver his rattling mixture of warbled notes.
I am not a fan of the song but that could have something to do with the fact that I am often the last to pick it up. Half a weedy note is enough to draw my attention to a Bullfinch but I find a Lesser Whitethroat in full song in the same hedge much harder.
Male Lesser Whitethroats start one or two nests, singing and displaying until a female becomes interested and joins him to complete the preferred cup. This will usually be within the prickly protection of hawthorn or bramble, in a tall, thick hedge containing occasional trees. Territories are quite large and males can move silently between song-posts up to 100 metres or 200 metres apart.
Early in the season, before finding a female, males may choose a song-post quite high up in a tree. Generally though, this is a secretive species and there are relatively few 10km squares in which we have proof-of-breeding for the atlas.
Over this summer and next, we hope that people will spend time looking into hedges – either trying to carefully locate nests or using binoculars to try to spot pairs of birds, adults with food or begging youngsters.
The breeding distribution of the Lesser Whitethroat reflects its eastern origins. Numbers thin out in the southwest of England and there are relatively few in Wales, where they are found mostly in the south, along the north coast and into Anglesey.
In the 20 years between the breeding atlases of 1968-72 and 1988-91, the species spread further up the east and west coast of England, moving into coastal areas of southern Scotland. Results from the Breeding Bird Survey indicate that there has not been much of a change in numbers since 1995 but, as the species occurs in fewer than 10% of survey squares, it would be hard to pick up a small-scale change in the population level.
Bird Atlas 2007-11 seems to be confirming a stable situation, with the species occupying similar areas to those shown in last breeding atlas, perhaps with some losses in the west. This is definitely a species to try to capture on the lists that you submit as atlas roving records or on BirdTrack.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
If you haven’t been following the Migrant Birds in Africa blog (http://migrantbirdsinafrica.blogspot.com), I urge you to do so. As I have mentioned before, severe and ongoing declines of many of our African migrants, such as Cuckoo and Turtle Dove, have led BTO and RSPB researchers to West Africa, to better understand the challenges that migrant birds face during the winter.
During the past few months, fieldworkers have been monitoring birds in five different areas, ranging from the semi-desert Sahelian region in Burkina Faso to the tropical rainforest in southern Ghana.
In the February instalment, BTO research biologist Mark Hulme wrote about listening to Nightingales while sitting on a tropical beach, and reflected that it had been worth battling through various challenges in order to collect such valuable data on our migrant birds.
To most people who are not active birdwatchers, Nightingales are near-mythical birds, celebrated in literature and poetry for their beautiful song (though I have to say that, to me, the most remarkable thing about Nightingale song is its sheer volume).
Their reputation certainly goes before them, for although everyone knows the name, few people in this country will have ever knowingly heard a Nightingale, let alone seen one. They are especially hard to find these days – previous BTO Atlases exposed a really shocking range contraction between 1970 and 1990, and figures from the Breeding Bird Survey show that Nightingales have declined by over 40% just since the start of the survey in 1994.
Provisional maps from the 2007-11 Bird Atlas show that Nightingales are now very sparse indeed – the core population has retreated to coastal areas of Essex, Kent and Sussex, with a few patchy and isolated records over their former range (south-east of a line drawn from the Wash to Exeter).
Thanks to research by BTO ornithologists, the habitat requirements for breeding Nightingales are well known – this species needs closed-canopy scrub, with areas of bare ground under the canopy, and also areas of dense low vegetation.
This combination offers safe foraging opportunities (on the bare ground), suitable nest sites, and cover from predators. However, changes in woodland management, increased grazing pressure by deer and loss of scrub habitats may all have caused a loss of this kind of habitat structure.
These factors are the subject of ongoing studies, including a project in which BTO researcher Chas Holt radio-tracked breeding Nightingales to see exactly how deer numbers affected the birds’ habitat use.
Although loss of suitable breeding habitat in England may go some way to explaining the decline in the numbers of Nightingales, habitat loss alone is not enough to account for such a dramatic change.
Many species that spend the winter in sub-Sahelian Africa, such as Willow Warbler, Cuckoo and Nightingale, are all showing severe declines, and this has thrown the spotlight on their African wintering quarters as a likely source of the problems.
BTO researchers are trying to find out exactly what is happening, and have started work on two exciting new projects – firstly, the ‘on-the-ground’ research in West Africa mentioned above, and secondly, a scheme designed to track individual Nightingales on their wintering grounds.
Twenty birds were caught in their East Anglian breeding grounds in 2009 and were fitted with geolocaters – tiny devices, weighing less than 1g – which will record exactly where the bird goes.
The aim is to re-catch the same individuals on their breeding grounds in 2010, remove the tags, and download the detailed information about where these birds spent the winter. Together with data from birds tagged in Switzerland, Italy and Bulgaria, this study should provide unique information on the wintering distribution of Nightingales, and will provide a focus for our work in West Africa.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
I have a picture on my wall, a wedding present, which is an impressionistic photograph of a flock of Pink-footed Geese by the Norfolk photographer (and fellow Bird Watching contributor) David Tipling.
The geese are just rising into the air, movement-blurred shapes with the odd beak – or pink foot – picked out in sharper focus. I don’t know exactly where the photograph was taken, but North Norfolk is rightly known for spectacular numbers of wintering Pink-footed Geese, which decorate the sky with long V-shaped skeins as they travel daily between their feeding and roosting areas.
Pink-feet have a limited world distribution, and breed only in Iceland, eastern Greenland and on Svalbard, divided into two separate migratory populations.
Birds that breed in Iceland and Greenland winter almost exclusively in Scotland and England, and birds from Svalbard travel through Norway and Denmark to spend the winter in the Netherlands and Belgium.
Our knowledge of the movements of these birds is thanks to extensive ringing studies, first in the 1950s by Sir Peter Scott and colleagues, and then in the 1990s onwards by the Wildfowl and Wetlands Trust.
Of all the Icelandic-breeding Pink-feet ringed in Britain and Ireland, and on their Icelandic breeding grounds, only a handful have moved to join the Svalbard population – but this is thought to be sufficient to allow gene flow between the two groups.
The Icelandic-breeding population has increased massively in recent years, thought to be due partly to better food supplies in the UK in winter, and the ban on the sale of shot geese in the 1970s.
According to the latest Wetland Bird Survey report, in the winter of 08/09 an impressively accurate 339,732 birds were recorded by volunteers in coordinated UK-wide counts, and it was estimated that the total population of Icelandic flyway Pink-footed Geese (the larger of the two populations) was over 351,000 individuals.
This was an exceptional 23% increase on the previous winter, and a high point at the end of a graph that has shown a continuous increase since the mid 1980s.
From ringing recoveries, it’s well known that Pink-footed Geese do not stay in one place during the winter months – they tend to shift around to different areas in the UK, and in December 2008 over half of the total wintering population was present in Eastern England.
My favorite place to watch the Norfolk birds is on the grazing marsh at Holkham, on the North Norfolk coast, but they are present on agricultural land across the whole area. One reason why the geese are so fond of Eastern England is the spread of sugar beet farming.
The leaves, stalks and tops are cut off before the crop is harvested, and are often left in the fields to fertilize the soil – a food supply irresistible to Pink-footed Geese, which are also attracted to the large open fields used to grow sugar beet. Farmers are now encouraged to leave the sugar beet tops on the fields, rather than ploughing them in, as this diverts the geese away from more valuable growing crops, such as winter-sown cereals.
In a flock of thousands of Pink-feet at Holkham, I generally see a number of ringed birds, many of which also wear plastic neck-collars, marked with a unique code of letters and numbers, readable through binoculars or telescope.
These are birds marked as part of ongoing studies into migration and movements of these winter visitors, and the ringers rely on sightings submitted by birdwatchers to further their research.
By sending in your sightings of marked birds, you will not only receive a full history of all the sightings of that individual, you will also be contributing to the knowledge of this important population of birds, for which we as a nation hold such great responsibility.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
In March, most of us eagerly await the sight or sound of our first returning summer migrant. One of our earliest arrivals is in fact a seabird – the Sandwich Tern. They can be seen around our coasts from late March, with the average date of the first BirdTrack sightings on the south coast being 22 March. This is an impressively early arrival, considering that many spend the winter as far away as South Africa, and have further to travel in the spring than most other migrants.
Sandwich Terns are larger and bulkier than the Common and Arctic Terns, which are known as the ‘sea swallows’ because of their long graceful tail streamers.
They have fewer breeding colonies than the smaller tern species, but they are even more strongly gregarious and nest at higher densities. Sandwich Tern colonies are widely scattered around the British Isles, although one place they no longer breed is at Sandwich in Kent, where their name originates.
As they are confined to a few well-known sites, you’d think it would be easy to monitor their numbers, but monitoring terns is never straightforward! The colonies generally remain at traditional sites, but the numbers of birds nesting at each site varies dramatically year-to-year, as birds make mass shifts between colonies. I
n addition, in bad years many birds will not breed at all, so the total breeding population, across all colonies, fluctuates markedly between years. It may seem odd that birds would take a ‘year off’ from breeding, but Sandwich Terns, like many seabirds, are very long-lived; recoveries of ringed birds have shown that this species can live for 30 years. This longevity means they can afford cut their losses, and save their energy for a future breeding season, if conditions are not ideal.
The difficult task of monitoring Sandwich Terns is carried out under the JNCC Seabird Monitoring Programme, which collects data on seabird numbers from partner organisations (including the BTO), and from volunteers.
The number of pairs breeding in the UK, while fluctuating, has not shown a consistent increase or decline since the 1980s, and is currently estimated at around 12,000 pairs. The population was previously much lower, as in the 19th century people collected eggs from tern colonies for food, before legislation made this illegal and the population recovered.
Future threats to breeding Sandwich Terns include predation by a variety of mammals and birds, and human disturbance. This species is also likely to be affected by climate change; warming sea temperatures cause changes in the distribution of their prey species, such as sandeels, and the birds are very vulnerable to rising sea levels, nesting as they do on low-lying ground close to the tideline.
Sandwich Terns also face threats outside the UK; their migration takes them around the populated coastal areas of West Africa, where many are caught in fishing nets. The local people are keen to report ringed birds, and many letters arrive addressed to ‘British Museum London’ (the address stamped on BTO bird rings) from Senegal, Ghana, the Ivory Coast and Sierra Leone. According to the BTO’s online ringing report, more British-ringed Sandwich Terns have been recovered in Senegal (782 birds) than in any other foreign country.
It’s amazing to think of journeys made by these elegant seabirds, and when I see my first Sandwich Tern of 2011 (and record it on BirdTrack, of course) I’ll take a moment to wonder just how old that bird is – and how far it has travelled.
Words: Kate Risely, of the British Trust for Ornithology (BTO)
Song Thrushes are one of our commonest garden visitors – or at least they used to be. BTO figures show that Song Thrush numbers have halved over the last 40 years, a decline sufficient to warrant ‘Red-listed’ status – but one that has probably gone unnoticed by many, as these birds are still very common, with more than a million pairs estimated to breed in the UK.
The most recent Garden BirdWatch reporting rates, however, may open a few eyes: during July-September 2009, Song Thrush was not in the top 10 most commonly reported birds, as might be expected, or even in the top 20 – in fact, it sits at number 22, recorded in just 14% of gardens, below Nuthatch and Magpie.
So what has caused this massive decline? The first step in identifying the causes of change is to find out which stage of the life cycle has been affected – are numbers going down because more birds are dying, or because fewer are hatching?
If it is because fewer birds are hatching, is it because fewer eggs are being laid in the first place, or because more nests are failing? The Breeding Bird Survey tells us whether bird populations are increasing or decreasing, but the BTO also runs a number of schemes investigating the demographics of bird populations, which aim to explain the underlying causes of the changes we can see.
BTO researchers have analysed demographic data from the Constant Effort Sites ringing survey and the Nest Record Scheme, and have shown that the drop in numbers can be explained by the fact that fewer young Song Thrushes are surviving their first winter, a time when experience counts if resources are scarce.
The environmental causes of these changes are not yet known, but changes in farming practices, land drainage, pesticides and predators are all possible contributors.
The picture becomes more complicated when you consider that Song Thrushes are found in a variety of habitats – mainly woodland, scrubland, and gardens – and will experience very different pressures on their populations depending on their immediate environment.
Those birds choosing to live in suburban gardens may have access to better food supplies, such as easily accessible worms in close-cropped lawns and bare flowerbeds, but they also have to cope with the problems caused by living in close proximity to people – and their dogs and cats.
As the suburban environment expands, gardens become an increasingly important habitat for birds. The BTO is currently investigating the nesting success of birds, like the Song Thrush, that commonly use gardens as breeding habitat, so we would like to hear about any nests you find.
If you have plenty of shrubs and creepers in your garden, you will probably also have a nesting Song Thrush or Blackbird – though they may not be easy to find! The nests of both species are surprisingly large, and can look quite messy on the outside, but can be told apart (if the parent bird is not in residence) by looking at the lining of the nest – a Blackbird nest is lined with dry grass, while Song Thrushes coat the inside of their nests with a smooth hard ‘cement’, which consists of mud and ‘chewed-up’ rotten wood.
Song Thrush eggs are bright blue with well-defined black dots, while Blackbird eggs are generally duller with red-brown speckles. While it’s important to avoid excessive disturbance of nesting birds, it’s perfectly safe to look into nests at intervals, and the BTO will be able to use information submitted by the volunteers about garden-nesting Song Thrushes to refine our investigations into the causes of declines.