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.