According to ongoing monitoring over the last 30 years through the British Trust for Ornithology, the numbers of many woodland birds in the UK have seen a sharp if not precipitous fall. What is the outlook for those most highly adapted tree-trunk-living birds, the woodpeckers? How are they faring and do forestry operations affect them and vice versa?
THE three everyday species of woodpeckers in these islands all excavate their own nesting holes in trees. They are the great spotted (Dendrocopos major), lesser spotted (D. minor) and green (Picus viridis). There is still some debate about if this class of birds might actually raise the risk of infection or rots entering healthy tree trunks in such nesting cavities.
Once upon a time, through their actions, these birds were believed to hasten rot and disease in healthy trees, but in the present, more enlightened era that is not believed to be true. There is little or no evidence for the theory and these birds drum on or chisel out nest holes mainly on branches or trunks that are already dead or decaying. And, even if it were so, it would be the least of foresters’ concerns.
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Two of the three species – the spotted ones – eat grubs and insects on the surface of the bark or dig down through the trunk to find beetle larvae, which must be a bonus to forest health, even if not so obvious as it often occurs way up in the canopy, out of human sight.
So what is the status of these three and their close cousin the wryneck (Jynx torquilla)?
ALREADY GONE!
A fourth member of the original woodpecker assemblage is the wryneck. Up until the 1950s, this migrant was regularly reported passing through each summer and occasionally bred, but is now feared extinct here although still present across on the continent.
This well-camouflaged woodpecker used to be a common breeding bird in Britain, yet is now only likely to be seen passing through on migration. Classed as a former breeding species under the Birds of Conservation Concern 5: the Red List for Birds (2021), it is protected in the UK under the Wildlife and Countryside Act 1981, as a Schedule 1 species.
This bird is mainly a ground feeder on ants and, unlike its relatives, does not chisel out a nest hole but relies on existing cavities, especially those once common in old and fast-vanishing traditional orchards and large unkept gardens.
The stocks and range of the sparrow-sized lesser spotted woodpecker have plummeted in recent decades. Experts agree to differ on exactly why this decline is underway – but competition with the GSW is cited – although no one factor will fit all situations.
This small bird lives higher up in the tree canopy, so is sometimes overlooked, and also drums on hollow branches but is more muted.
The largest of the UK’s resident woodpeckers and the least arboreal is the green, whose main diet is ants. Its main mode of communication is not by drumming on hollow branches as sounding boards but by its laughing call – hence its old country name of the ‘yaffle’. Like its cousins, it does nest in tree holes that is digs out itself.
Its numbers have stayed roughly the same over the past decades, faring better in some counties than others. Famous last words, but there seems no cause for concern overall.
NUMBERS CLIMBING
Some good news for once! The great spotted (GSW) is one woodland bird inhabitant that is actually on the up – and its regular visits to bird tables in gardens for nutritious fatty foods in the ever-more-common milder winters are often cited as a factor favouring this bird.
The Wildlife Trusts note that over the last few years, the great spotted woodpecker has started to nest in Ireland for the first time. It has also developed an appetite for the taste of red meat, forcing an entry into wooden nest boxes to prey on small nestling birds, and will carve out drill holes in wooden nest boxes to consume the young.
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions.
One of the most notable is the acorn woodpecker (Melanerpes formicivorus) of North and Central America. Acorn woodpeckers are cooperative breeders, living and breeding in family groups of up to 15. Each autumn they collect and store acorns in small holes drilled especially for this purpose in ‘granaries’ or ‘storage trees’ – usually snags, dead branches, utility poles or wooden buildings. Storage holes – always in dead tissue such as bark or dead limbs – are used year after year, and granaries can consist of thousands of holes, each of which may be filled by an acorn in the autumn to hoard for winter food supply.
Sapsuckers are woodpeckers with a sweet tooth. As their name implies, sapsuckers feed primarily on the sap of trees, moving from one species of tree or shrubs to another as the seasons change.
SO WOODPECKERS GET HEADACHES?
Woodpeckers are often heard before they are seen. The drumming of a GSW is a familiar and evocative sound reverberating in our woodlands, parks and gardens. It is a form of communication mainly used to mark territories and display in spring.
The lesser spotted woodpecker also drums, but in a more muted fashion, and from the canopy of tree tops where it searches for invertebrates.
Sensible modern tree workers employ adequate ear protection to look after their sensitive hearing when using noisy tools and machinery, but what about woodpeckers?
Chipping away for long periods digging out either grubs or nest holes, or advertising their own presence must surely put a strain on the brainbox. How do they guard against repetitive strain injuries?
These birds have a special anatomy so that all the hammering away does not give them a headache. In lay terms, they have a special bone in the head that acts a bit like a seat-belt for the skull. Called the hyoid bone, it wraps all the way around a woodpecker’s brain case. Every time the bird pecks, this adaptation acts like a restraining protector for the bird’s skull and the delicate brain it protects.
In addition, their upper beak is just slightly longer than its lower one, kind of like an overbite. But should you ever peer inside, you would find that the lower beak has a longer bone. So that ends up taking on most of the strain when hammering. This helps to absorb impact while chiselling away and diverts the force down onto the body instead of the brain.
NEST BOXES AND MAN-MADE HOLES
Across the planet, some conservation bodies do take a chainsaw to mature trees to carve out artificial nesting cavities for woodpeckers. If the budget stretches to it, birdboxes for woodpeckers are available on the UK market – and as an extra you can provide and mimic the woodchip nesting material found on the floor in real DIY holes where no other nesting material is brought in by the birds themselves.
More dead trees does not however mean more woodpeckers – territorial claims may need minimum area. Competition for nests sites with other hole-nesting usurpers or squatters such as jackdaws, owls, hawks and, in Greater London the alien ring-necked parakeets, has been documented.
The reasons behind those are often complex, but high on the list of adverse factors is the lack or decline of woodland management practices – especially coppicing – coupled with spiralling and spreading numbers of hungry deer. But there is no universal ‘one-size-fits-all’ explanation.
LOOKING AHEAD
Treed habitats change over time – as do the species of bird and the numbers that call them ‘home’. Those changes may be gradual or quite abrupt in terms of a tree’s life compared to a feathered friend. Think back to the drive to plant conifers and the creation of the Forestry Commission, Lawson tax breaks, Dutch elm disease, the current push on woodland expansion and an anticipated boosted broadleaf component.
And with the spread of ash dieback nationwide, more dead standing timber should be in abundance offering more real estate for GSW in terms of both insect food and sites ripe for development as des res nesting holes.
Nowadays, many broadleaf woodlands contain more standing deadwood than in the past as foresters are persuaded to leave such material for its biodiversity value and not be over-tidy. More snags and dead branches might appear to offer greater opportunities for woodpeckers, but the carrying capacity of broadleaf or mixed stands may not be limited by those factors but by territorial behaviour that may determine population size and when a site is full. Watch – or listen to – this space.
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