1 AQUILA VOL.: 102 (61-67) IDENTIFYING THE PRESENCE OF WOODPECKER (PICIDAE) SPECIES ON THE BASIS OF THEIR HOLES AND SIGNS Gerard Gorman Abstract Gorman, G. (1995): Identifying the presence of woodpecker (Picidae) species on the basis of their holes and signs. Aquila, 102, p Eiglű species of true ivoodpeckers (Picidae) are resident in Hungary. In addition to finding and identifying woodpcckers by call the author proposes that a knowledge of the typical signs left by each species can be most useful in establishing which species are present in a given area, particularly in winter when birds are often less vocal and mony tree species defoliated. Tlie typical feeding signs, nesting-hole locations, average hole heights and preferred tree species of each species are presentcd. Though the feeding habits and feeding signs left by most of the species mentioned arc not entirely diagnostic, the careful examination ofsuch signs and the type of woodland where they arc found can often eliminate several species. Thus the identity of the zvoodpccker species present can with somc rcliability be narrowed down to one or tivo species. Nesting-holes on the other band are often relativcly easy to assign to a species, if not, to closely related congeners. Tliough on a European scale Hungary is a rather lightly forested country with a total arca of woodland of around 18%, the occurrence of eight out of the nine Picidae present in Europe means that the country is important for the family. Despite this the forest nj practices ofboth the former ccntralized system and the present market orientated cconomy did not and do not (with certain exceptions) favour the maintaining of ideal woodpecker habitats. Key ivords: bark, canopy, cavities, coniferous, deciduous, Dendrocopos, nesting-hole, Picus, trunk, woodpcckers. Introduction An indispensable, but often neglected, field-craft skill which assists in locating birds is a knowledge of bird signs (Brown et al, 1987). With the exception of feathers, conspicuous nests and the pellets of raptors and somé other birds, most birds leave relatively few discernible signs of their activity and are thus often more easily located visually or by songs and calls. However, the breeding and feeding behaviour of one family, the woodpeckers Picidae, inadvertently leaves a trail of evidence for ornithologists and birdwatchers to follow. In my experience i-t is not possible to definitively attribute all the holes and signs found in a particular woodland to a particular woodpecker species, but a knowledge of these signs and of the habitat preferences of each species can often result in a confident assertion of which woodpeckers are present in a given area. 61
2 Gorman, G (1995) In winter when many trees have shed their leaves finding and examining the marks left by feeding woodpeckers and nesting-holes previously concealed by the canopy can be particularly rewarding. Despite many signs being impossible to accurately identify others are unique to particular woodpecker species. The following is a summary of those signs which I have found to be useful in tracking down the eight species of true woodpeckers found in Hungary. The alpine species Three-toed Woodpecker (Picoides tridactylus) is not covered as it does not occur in Hungary. I also made use of notes made in woodlands in Austria, the Czech Republic, Slovakia, Poland, Románia and the UK. Grey-headed Woodpecker (Picus canus) Species Nest-holes of this species are almost always well above 3 metres on the main trunk of mature trees in large Stands. Occasionally holes are excavated in telegraph poles: in 1994 I observed a male visiting a roadside telegraph pole near Arka in the Zemplén Hills. Nest-boxes are also occasionally used, entrance holes meant for songbirds being enlarged. Greyheaded Woodpeckers seem to prefer beech (Fagus sylvatica), oak (Quercus spp.), aspen (Popidus tremula), hornbeam (Carpinus betulus) and lime (Tüia cordata) (Cramp, 1985) but will also sometimes excavate nesting-holes in willows and conifers. Being essentially a ground feeder, stabbing and probing marks in soil, turf or ant-hills often indicate the presence of the species, though these signs are difficult to separate from two other ground feeders, Green and Black Woodpeckers. Grey-headed Woodpeckers, however, feed rather by licking and gleaning and thus tend to leave less bark and wood waste around stumps and ground feeding sites than the two mentioned species. Though they regularly feed in trees extensive workings are rarely done by Grey-headed Woodpeckers and they apparently do not ring" or drill holes to get at sap (Winkler et al, 1996). Green Woodpecker (Picus viridis) This species invariably excavates nest-holes on the main trunks of old deciduous trees. Holes can be as low as 1 metre above the ground, though are usually between 1.5 and 2.5 metres. The species seems to require softer or more rotten wood than Grey-headed and Black Woodpeckers (Cramp, 1985). The species also occasionally uses nestboxes after enlarging the hole (Gorman, 1996). Green Woodpeckers seldom riddle a tree with large, deep cavities rather they strip off, prise up or chisel away bark. They also wedge pine cones in crevices and peck 62
3 Identifying tlie prcsence of woodpecker them open there. Discarded small sods and numerous dents, ruts and holes in turf or soil and are also typical. A crudely destroyed fallen trunk or log is more often than not the work of a Green Woodpecker searching for invertebrates rather than its congener Grey-headed Woodpecker. Green Woodpeckers will also bore holes (sometimes tunnellike) into anthills and dig through snow to get at buried food sources (Cramp, 1985) (Winkler et al, 1995). The species is less attached to thick forest than Greyheaded Woodpecker and avoids coniferous Stands preferring oak Qucrcus, beech Fagus and larger willows Salix. Black Woodpecker (Dryocopus martius) Typical nest-holes of this species are on wide trunks, in hard, sound wood and on average 7 metres high though they can be as low as 3 metres and as high as 16 metres. The species often selects the largest trees in a given area (Carlson & Aulen, 1990) and the majority of nestingholes are in living trees. A clearly visible, large oval entrance hole, with trial holes of similar size on the same trunk, is typical. Black Woodpeckers will use old nest-holes for both nesting and roosting. Favoured trees are beech (Fagus spp.), spruce (Picea abies), pine (Pinns sylvestris) and poplar (Populus spp.). In woodland proper (where in Hungary Green Woodpeckers seldom occur) any signs of prolonged work on stumps or on the ground at ant-hills, with a mess of leaf-litter, large wood chips and rotten debris scattered nearby, indicates the presence of the species. In winter, swished away snow and deep holes around ant-hills is also the work of the species (Cramp, 1985). As Black Woodpeckers work for several days at favoured feeding sites accumulations of debris are typical as are large strips of levered off trunk (rather than log) bark and completely hacked out tree bases. In Hungary the presence of Stock Doves (Columba oenas) indicates Black Woodpeckers are resident as the former relies on the later for nesting cavities. Great Spotted Woodpecker (Dcndrocopos major) The nest-holes of this generalist species are usually above 2 metres on the main trunk, large verticai boughs or even telegraph poles, in woodland, plantations, parks, gardens, indeed, just about anywhere with trees. Nestboxes are often beaten-up and sometimes used for breeding. One of the most characteristic signs made by Great Spotted Woodpecker is the ring" or girdle" around a tree trunk (Cramp, 1985). These lines of holes are made to get sap. Great Spotted Woodpeckers also excavate holes all year round. Fresh holes outside the breeding season are invariably made by this species. The species rarely excavates trees to a significant depth to find food, doing 63
4 Gorman, G (1995) this only in rotten wood. The species prefers to strip off or lever off bark, to probe and peck the surface or hack at dead wood. Great Spotted Woodpeckers rarely make holes in the ground or visit ant-hills. Another typical sign of the species is the anvil" or Workshop" (Cramp, 1985, Winkler et al, 1995). This is a regularly visited split or crevice (natural or made by the bird) in a tree or log where pine cones are opened. Cones and nuts are left in such places after feeding has finished. Often large piles accumulate. The species also attacks nest-boxes at the base or a jóin in order to predate on the young songbirds within. Rotten stumps which have been opened up to rob the contained passerine broods, particularly of Parus species, also invariably betray Great Spotted Woodpeckers. Syrian Woodpecker (Dendrocopos syriacus) The nesting-holes of this species can be as low as 1.5 metres but are usually around 2 metres above the ground on the main trunk or a larger side bough. The species will occasionally take to nest-boxes. Acacia (Robinia pseudoacacia), poplar (Populus spp.), walnut trees, cherry and other fruit trees are often favoured for nesting sites (Gorman, 1996). Syrian Woodpeckers also use anvils" or Workshops"(Winkler et al, 1995) where almonds and other food items are wedged and cracked open. In 1994 I observed a Syrian Woodpecker clinging to a garden wall by the Danube and wedging nuts into cracks between the stones (Gorman, 1995). In generál the signs and holes made by this species cannot be easily distinguished from those of its near relative Great Spotted Woodpecker. However, Syrian Woodpeckers tend to work more on softer wood and I have found no evidence of the species feeding on pine cones or predating on songbird chicks. Syrian Woodpecker also avoids thick woodland, rarely nesting away from secondary habitats such as parks, orchards, cemeteries and gardens. Middle Spotted Woodpecker (Dendrocopos medius) The nesting-holes of this species are usually on side branches, often on the underside, though sometimes rotten upper trunks are excavated. They can be located as high as 4 metres though between 2 and 3 metres is usual. The species probably also uses old holes and occasionally uses nest-boxes intended for other species. Middle Spotted Woodpeckers prefer Stands of oak (Quercus spp.), mixed oak-hornbeam (Quercus-Carpinus betulus) and occasionally frequents old orchards (Cramp, 1985). The species feeds mainly in the crown, gleaning insects from foliage and on branches and trunks the species probes lightly into bark and does not bore deep into wood. Loose bark is peeled off or prised away. Otherwise this species leaves very few, if any, typical signs which can be distin- 64
5 Identifying the presence of woodpecker. guished from those made by other woodpecker species. Very rarely seen feeding on the ground (Winkler et al., 1995) the species will attend bird tables. I have no evidence of this species using anvils" or Workshops". Wlúte-backed Woodpecker (Dendrocopos leucotos) The holes and signs of this the rarest woodpecker species in Hungary are somé of the most typical and diagnostic of the family. Nesting cavities are often just below a branch, a growth or bracket-fungus, from between 4 to 12 metres above ground. New nesting holes are usually excavated annually though old holes are used as roosts (Carlson & Aulén, 1990). White-backed Woodpeckers strip bark and work the trunks beneath producing evenly worked large bare surfaces as if done by a carpenter with a mailét and chisel. Conical holes are also typical. These are often low down near the base of the tree and can be deep enough to almost hide a working bird from view. Preferred trees include aspen (Populus trcmula), alder (Alnus glutinosa), birch (Betula spp.) and beech (Fagus spp.) (Cramp, 1985). White-backed Woodpeckers are specialist in feeding on rotten wood (Winkler et al, 1995) and are indeed the most specialist in habitat choice and feeding habits (Carlson & Aulén, 1990). The species feeds mainly on dead and rotting stumps and trunks, often at ground levél. In 1994 I observed a male pecking at the cement between bricks in a ruined wall in the Börzsöny Hills. Lesser Spotted Woodpecker (Dendrocopos minor) The nest-holes of this species can be found at almost any height, usually in rotten wood on a side branch but also occasionally in a large bough, trunk or rotten stump. The usual height is between 2 and 3 metres. Nestboxes are also regularly used (Winkler et al, 1995) in places where they are plentiful, such as songbird study areas. Prefers mixed deciduous woods, especially oak Quercus spp, with plenty of decaying wood (Cramp, 1985). Also frequents orchards, gardens and floodplain forest of willow (Salix spp.) and to a lesser extent (Populus spp.). Being mainly a canopy feeder, gleaning insects from foliage and loose bark the species leaves few signs which are unique to itself and which can be safely distinguish from those of its congeners. The species rarely feeds at lower levels or on the ground though will attend bird-tables in winter. 65
6 Gorman, G (1995) Conservation In Hungary forests of one kind or another cover somé 18% of the total land surface. In European terms this is relatively low but despite this forestry has a long tradition in Hungary and as a result no virgin tracts remain (Csóka, 1994). It is well known that virgin forests have a higher density of hole-nesting bird species than managed forest, sometimes up to three times higher. Tree composition, tree age and the amount of dead or decaying wood are all very important for hole-nesting birds (Avery & Roderick, 1990). In 1930 around 12% of the country was forested and a steady policy of afforestation has seen the area covered rise by 6% to the present figure. The vast majority of forest consists of broadleaved tree species. Postwar forestry practises (that is, those conducted under the former communist system) concentrated on planting fast-growing monocultures of alien species, often poplars. Most of such woodland is unsuitable for woodpeckers though the more generalist species such as Great Spotted and Green Woodpeckers have occupied plantations in somé areas. Such woodland however is far from prime habitat (Avery & Roderick, 1990, Carlson & Aulén, 1990). In addition natural deciduous forests, especially those of beech, have been felled in many upland areas and not replaced. As a result large tracts of forest in Hungary are essentially poor woodpecker habitat. White-backed Woodpecker numbers in particular have fallen in such areas and Grey-headed Woodpecker numbers have also almost certainly been affected. The post-communist economic system has as yet failed to address the problems of profit orientated forestry management. The trend of selling off State run woodlands to private business may well add to the existing problems rather than solve them. It is feared that one of the consequences of private ownership in logging may be an increase in uncontrolled feliing. Though overall there is a trend towards afforestation in Hungary as agricultural land is abandoned the planted forest is largely unsuitable for woodpeckers and indeed all hole-nesting birds. The careful monitoring of woodpecker populations (and of all woodland birds) by ornithologists and conservationists in the country will be needed. Acknowledgements The author's research for this article was in part supported by a grant from The Eric Hosking Trust, UK. 66
7 Identifying the presence of woodpecker. References - Irodalom Avery, M. and Roderick, L. (1990): Birds and Forestry. Poyser. p Brown et al. (1987): Tracks & Signs of the Birds of Britain and Europe. Helm. p Carlson, A. & Aulén, G. (eds) (1990): Conservation and management of woodpecker populations. Uppsala, p Cramp, S. (ed): (1985): The Birds of the Western Palearctic, Vol. IV. Oxford, p Csóka, P. (1994): Forestry in a transitional economy: Hungary. Unasylva. Vol 45. p Gorman, G. (1995): Balkáni fakopáncs (Dendrocopos syriacus) kőfal rését használta satuként. Mad. Táj., július-december, p. 39. Gorman, G. (1996): The Birds of Hungary Helm, London, p Winkler, H, - Christie, D. A. - Nurney D. (1995): Woodpeckers: A Guide to the Woodpeckers, Piculets and Wrynecks of the World. Pica Press. p Authors address: Gerard Gorman Budapest, Pf. 701 H-1047 Hungary A Magyarországon költő harkályok fészekodúinak és vésésjeleinek" faji jellegzetességei Gerard Gorman Európa kilenc valódi (Picidae) harkályfajából nyolc állandó faj él Magyarországon. A különböző fajok által táplálkozásuk során, illetve odúkészítéskor hagyott jelek és nyomok sokat segíthetnek abban, mely fajok vannak jelen az adott erdőrészletben. Télen, mikor a harkályok kevésbé adnak hangot, és a lombjukat vesztett fák is megkönnyítik a keresést, a harkályok által hátrahagyott nyomok dokumentálása sok segítséget nyújthat. Szerző röviden összefoglalja a harkályfajok védelmi vonatkozásait, különös tekintettel a hazai erdőgazdálkodás fényében. A közlemény anyaga elsősorban a szerző tízéves magyarországi megfigyelésein alapul a Duna mentén, továbbá a Vértes, Budai-, Börzsöny, Pilis és Zemplén hegységekben, melyet egyéb európai megfigyeléseivel és az irodalom adataival is összevet. 67
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