Where did the birds around us right now come from? They might have travelled further than you think
By Dominic Couzens
How do you assess a birding trip? There are various ways, such as counting the number of species you have seen, or re-living good photos that you took. You might have seen something new for the site, or you simply enjoyed the spectacle. On a good day, all these might apply.
However, let’s imagine measuring a birding trip in a very different way. This way is actually not quite possible, but if it was, it would change one’s perception radically. Imagine that, from the moment you set eyes on it, you could know where every individual bird that you saw has come from.
In other words, you would instantly know where it bred or hatched during the summer, and what journey it undertook to get to you. Wouldn’t that make you look at your Black-headed Gulls or Mallards differently!
Now would be a particularly good time to exploit such information. We are in the depths of winter and most birds have settled down for a while. In the months after breeding, many moulted and travelled to their winter quarters.
Now, though, as long as there aren’t any heavy falls of snow, birds have typically moved as far as they will for the moment. The autumn rush has finally subsided, to be replaced by a Christmas quiet.
There is no way to follow a bird’s tracks back, but actually, thanks to the rich heritage of ringing in this country and in Europe, we can make a much better educated guess than you might think.
Two winter bird walks
To illustrate this, I am going to take you on two winter walks. One will recount an actual walk that I have taken in my local patch, a couple of small reservoirs next to a river in Dorset, 10km inland. The second is a walk through a book, the BTO’s mighty Migration Atlas, published in 2002 and summarising the known movements of every British bird.
To quote one example from the book, of Redwings controlled (caught, having been ringed earlier) in Britain, 60% are known to be from Finland, 14% from Sweden and 5% from Norway. This is raw data and subject to all sorts of bias – there isn’t much ringing in the vast forests of European Russia, for example.
But, since the first birds I saw on my walk were a small flock of Redwings passing over in the grey, damp December sky, I am fancifully going to extrapolate: of my 15 Redwings, I reckon that nine are from Finland, two from Sweden and about three-quarters of the other bird is from Norway.
Although I will never know, and it would take enormous effort ever to find out for sure, my estimate is still based on real statistics. It does have a value in making you realise where our winter birds are coming from.
My next species, inevitably, is Black-headed Gull. The lakes are often carpeted with these gulls in the winter – up to 400 birds. To be honest, on most trips I barely notice them, and rarely can I be bothered to count them.
Let’s face it – who really does bother with Black-headed Gulls? In fact, though, their origins are thoroughly mixed, so they are a particularly good candidate for this kind of exercise.
We have significant colonies in Dorset, so it is extremely likely that some of my flock will be local birds. But perhaps what many birders don’t realise is that Black-headed Gulls arrive in large numbers in winter from many parts of Europe and that about 70% of the birds we see in winter are visitors.
These are mainly from Fennoscandia and the near-continent, but others are from less obvious places such as Poland, the Czech Republic and Belarus. My flock could contain birds of nine or 10 nationalities.
Blackbird, Chaffinch, Great Crested Grebe and more…
A Blackbird scoots past into the nearest scrub – about a quarter of our visiting birds are from Norway, so if I later see a small group of Blackbirds feeding in the horse paddocks beside the lake, I can assume that at least one is from there.
Chaffinches are an interesting case, because you can usually tell that they are continental visitors from their behaviour. The really big flocks of Chaffinches on arable fields and in woods are usually visitors, while residents tend to occur in smaller parties and don’t wander.
Our birds are often from Scandinavia, but they don’t like the long crossing over the North Sea, and prefer to fly down the coast of Europe and make the short hop over from France.
A quick check of the first reservoir throws up some Great Crested Grebes – they often come to larger waterbodies in winter when the smaller ones freeze up, but they are all probably local.
Some of the Tufted Ducks also bred here, but others are likely to be from Norway and Finland. They have a few Pochards among them, too, and here I can add some hard data to the mix. Last year, we recorded a female fitted with a band on its bill, proving that it had commuted here from northern France, where it was a breeding bird.
This individual clearly hadn’t read the right books, because these birds are supposed to migrate south and west in winter, not due north. Many of our winter Pochards actually come from Latvia.
As usual, I check the flock for our lone winter Scaup, and eventually find it loafing among a flock of Tufties. This is one of the visitors that most probably comes from Iceland, along with our Snipe and perhaps a few Teals and other northern ducks.
Along the shoreline, a Pied Wagtail feeds. It might be sharing the same space as the nearby ducks, but ringing suggests that this bird could well be Scottish, evacuating the hills and glens for a shoreline in southern England.
I could go on. I hear a Water Rail, not realising at the time that it could be a German bird. A Sparrowhawk passes over and, to my great surprise, I read from the Migration Atlas that it could easily be from Norway or Denmark. The local Grey Herons could be from almost anywhere, and every winter we have an inexplicable influx of local Little Egrets, just for a few weeks.
In my local patch there happens to be a programme of ringing. It is exciting when we have a ‘control’ from somewhere like France or Portugal, but in a way it is the local and semi-local birds that are the most intriguing.
For example, our breeding Reed Buntings literally evacuate the site and go just a handful of kilometres down to the coast. We have controlled a Cetti’s Warbler that was ringed in Yorkshire – not only are they not supposed to go in that direction, but they aren’t meant to fly that far, either.
That’s the beauty of this form of fantasy birding. Who would expect a ‘sedentary’ bird to embark of such a strange movement? And who can imagine where all the other individuals have been?
One thing is for sure. If you really knew where all the birds had come from, you wouldn’t look at them in the same way, however common they were. If this form of birding ever became possible, it could catch on.