Green Woodpeckers and the Wildlife Sound Recordist
by Philip Radford
If an artist, who had been asked to design and paint an imaginary bird, submitted a picture similar to an adult Green Woodpecker Picus viridis, it could well be dismissed as being far too fanciful.
The pattern and colouring of a male Green Woodpecker in early spring is really striking, at least to me; with its greenish back, yellow rump, black and white primary wing feathers and a bright crimson crown patch, it does seem to have a garish colour mixture. Further, the male has a red centre to its black moustachial stripe, while the white eye is accentuated by a surrounding black patch. Even so, these varied colours, on what is the largest British woodpecker species, appear so correct when the bird is seen clinging to the bark of an ancient oak or probing for food on grassland. At a distance, the adult female cannot be distinguished from the male, although she does lack the red on the moustachial black stripe; the juvenile, perhaps as expected, is mottled and paler in colouring overall. Generally speaking, the Green Woodpecker lives on a diet of various ant species as well as on wood-boring insects; these food items are necessary if the bright feather colours are to be produced.
Listen to Philip Radford's' recording:
Not uncommonly, one may come across a scattering of feathers where a Green Woodpecker has been killed by a Sparrowhawk Accipiter nisus or, sometimes, one may be asked to identify separate feathers which have been found. If the feather has green on it the answer is simple, but it is not so easy if only one wing or tail feather is available. A tail feather is stiff and pointed, with white or pale green spotting; a wing primary feather is blackish with white spots and very like an equivalent feather of a Little Owl Athene noctua or even a Sparrowhawk.
Of course, the rigid, pointed tail feathers give a clue as to the bird's way of life. The ten feathers of the tail make an efficient prop so that tree trunks can be ascended, with stops for bark searching and feeding; the bird does not descend a tree head-first like a Eurasian Nuthatch Sitta europaea but may go down a short distance backwards. With woodpeckers, the foot has two forward and two back-pointing toes, each with needle-sharp claws, so a secure grip on bark is no problem. In appearance, the Green Woodpecker can be confused with the Golden Oriole Oriolus oriolus, but only with a female or a juvenile; the adult male is far too yellow a bird for a mistake to be made, as well as being a smaller bird. Then, in central and eastern Europe, there is the Grey-headed Woodpecker P. canus, which may co-exist with the Green Woodpecker in wooded areas. When compared, the Grey-headed Woodpecker is smaller with quite a tiny crimson crown patch and, in general, the green aspects of the plumage have a greyer quality.
Old rural names for the Green Woodpecker suggest the association with the springtime call or, probably, song. The best-known name, which is still used, is 'yaffle' or 'yaffler', from the whinny or laughing type of vocalisation, while the little-used 'high-hoe' must also have an onomatopoeic origin. Back in the 18th Century, Gilbert White (1789) wrote that the bird sets up a "sort of loud and hearty laugh" although I do not think the term 'yaffle' was used. In addition, there are other names, such as 'rain-fowl', 'rain-bird' or even 'wet-wet', which suggest that rain is in the offing when the yaffle song is heard. However, rain showers are commonplace during springtime in Europe so, personally, I do not have much faith in the Green Woodpecker as a weather forecaster, moreover, I have certainly heard good yaffling during April dry spells. Still, I believe that some of the old Roman writers referred to 'pluviae ayes' but did these supposed portents really relate to the Green Woodpecker?
The Green Woodpecker is largely a sedentary species which is found where there are mature, deciduous trees, whether in woodland (not too dense) or on parkland. England and Wales are well-populated by the bird and there is extension northwards in Scotland. Ireland is not occupied but the bird is well-distributed on continental Europe. We see the bird in its strongly undulant flight, caused by wing-closures between bouts of vigorous wing movements; unsurprisingly perhaps, Gilbert White (1789) referred to this as 'voluta undosa'. As a clergyman in the 18th Century, Gilbert White would have received a classical education and he often expressed himself in Latin which few writers on birds would dare to do nowadays! Apart from trees, we often see Green Woodpeckers, always very wary, on the ground on grassland or on lawns, where they probe to find ants and leave deep holes to annoy the gardener. Furthermore, the woodpeckers will attack ant-heaps in the woods; these breeding colonies are largely composed of leaf fragments mixed with conifer needles. Should the wildlife recordist plant a microphone nearby, a feeding woodpecker could provide a most interesting mechanical sound recording. But there is a problem here; wood-ants will spray formic acid if threatened, and this can etch the surface of a microphone as well as being an annoyance to the observer, who may get a few nips in addition. Nevertheless, ants seem to be prized items of food for Green Woodpeckers and one may find the characteristic cylindrical droppings in their haunts. These droppings are composed of pieces of chitin, as ant remains, and are enclosed in a greyish jelly membrane.
When feeding, Green Woodpeckers flick out their long, worm-like rod tongues to capture food items which stick to the tip. It is the tongue which collects food for the bird, not the large, pointed triangular bill. The tongue is attached to the curved horns of the hyoid bone, situated in the neck, by tough muscular strands; when not being used, it remains coiled up in the mouth cavity, round and like a thin eel. Glands are present on the tongue which produce a highly sticky saliva, while at the end there is a collection of back-facing barbs; thus, ants get trapped and held at the tip. When an ants' nest is opened, larvae, pupae, and eggs are all eaten as well as active adults. At a distance, it is not easy to see the rapidly moving tongue as it is extended, even when powerful binoculars are used; however, much less effort is required to spot tongue movements by well-grown young as they peer from their nest-hole, anticipating the return of a parent with food.
As well as ants, Green Woodpeckers feed on bark insects; damaged or diseased bark is struck and opened with blows from the sturdy, pointed beak. Insect pupae, larvae and spiders are certainly eaten and I have watched a juvenile taking trapped flies from a spider's web. The sounds of a Green Woodpecker exploring a tree, with bark tapping to get at wood-boring insects, gives a worthwhile recording sequence. In addition, berries from various plant species are eaten by Green Woodpeckers, although access to them may be a problem.
If one wants to record Green Woodpecker vocalisations, it should be remembered that the birds get up rather late, as they normally roost in dark cavities. The early dawn chorus is about finished when Green Woodpeckers become active; even so, yaffle sounds are best heard soon after this, especially during March and April. The yaffle-call, really a song phrase, is a series of high-pitched, laughing notes with a ringing quality: 'quu, quu, quu ...'. I think the yaffle is a most attractive advertisement or territorial vocalisation and it is always highly evocative, at least to me. Probably both sexes of the bird will yaffle, either when clinging to a tree trunk or during flight. On one occasion, when I was under a large ash in April, I heard what I assumed was rivalry between two males. Some yaffling calls were certainly uttered by both birds, just a few metres up in the tree, and additionally, there were sharp cries which suggested aggression. This sound interchange, of amazing amplitude, continued for nearly two minutes before one bird flew off, to be chased by the other; I had no microphone at the ready, so a fine recording opportunity was lost. In danger situations, characteristic and distinct calls are given and emphasised; such cries, frequently repeated, are commonly heard when there are young in the nest cavity, or have recently flown. These high-frequency 'c-uu' notes are surprisingly loud too. Further, as a flight-call, a short, sharp 'chik' is given, which sounds very like that of the Great Spotted Woodpecker Dendrocopos major. Furthermore, short, repeated whistles are sometimes heard, probably as contact calls with young or with a mate.
I used to believe that Green Woodpeckers never drummed but, in fact, it is certain that they may do so. Weak, infrequent drumming can be carried out by either sex, with a duration of about one second but it never seems to match the intensity of the Great Spotted Woodpecker's performance. Of course, Lesser Spotted Woodpeckers D. minor drum regularly in spring, again staking their territorial claims; the duration is around two seconds with 10-30 beats and a lower amplitude than the larger species. In contrast, the Great Spotted Woodpecker's drum roll is around eight beats although, naturally, there is much variation.
Green Woodpeckers are shy, retiring birds where people are concerned, when they vocalise it is often during flight, from leafy cover or from the other side of a tree bole. One mechanical sound which is surely worth recording is the excavation of a nest-hole, and this can be carried out by male or female. As expected, the Green Woodpecker's circular nest-hole is the biggest of all the British woodpecker species and, usually, a fresh hole is bored out each year. Fresh wood chips below a tree give a clue, as well as pecking sounds which, commonly, are far too distant for definite localisation, at least as far as I am concerned; anyway, late March or April are the times to be on the alert. The nest height varies, but is usually a few metres up in the selected tree trunk. Oak is a favourite, commonly with some rot inside the trunk, although any frondose tree of suitable size is a possibility. Clearly Green Woodpeckers are expert at assessing the degree of rot in an affected tree; Great Spotted Woodpeckers seem to select tree trunks in far greater states of disease and decay.
The five or six white eggs are laid at the bottom of the shaft, which is directed downwards from inside the entrance hole; the incubation period is about 18 days. There is only one brood, with the young spending about three weeks in the nest cavity; the adults are often very vocal at this time. The young are fed by regurgitation; I feel that the food-begging cries of the nestlings, with a hoarse quality, are highly attractive, with the sounds intensifying as age increases. The time when the young leave the nest, really a scrape amongst wood chips, is when the wildlife sound recordist ought to be nearby, and with apparatus fully prepared too. Varying calls of encouragement, usually mixed with warning cries, can give a worthwhile sound picture. Unfortunately, the departure hour is very difficult to predict! Doubtless, any sounds made by this retiring and highly attractive bird species, and which can be collected by the recordist, are of value in understanding the way of life of the colourful Green Woodpecker.