Most birds are located visually or by call, however some birds leave visual clues that betray their presence. These signs include footprints, feathers, and pellets and, of course, nests. Perhaps more than any other bird family, woodpeckers leave a variety of obvious signs that indicate that they are present in an area. Holes in trees, feeding marks on stumps, logs and trees, anvils, food stores, wood-chips on the ground beneath holes, all of these are a result of woodpecker activity. Many of these signs are unique to certain species, indeed in some cases they can be described as diagnostic. Knowledge of such signs, together with tree and habitat preferences, can lead to a confident assertion of which woodpecker species are present in a given area. In winter, when woodpeckers are less vocal, such signs are very useful clues. Indeed, winter is an excellent season in which to search for, and study, such signs as most trees are without leaves and so signs are easier to discover.
Above: A typical feeding site of White-backed Woodpecker. A finely shaved rotting stump, from top to ground level and with powder-like debris. Bükk Hills, Hungary (Szabolcs Kókay)
Nest-holes: Holes are the most recognisable sign of woodpecker presence. There can be a significant turn over of holes in an area each year. Some are lost, as trees are felled or storm damaged, and new ones created. Old holes become unsuitable due to wear and tear, filling with water (from melting snow or rain), become infested with parasites, clogged with fungi or are usurped by other birds, mammals or wasp, hornets and bees. Some woodlands (for birds and birders high quality woodlands, for foresters low quality woodlands) are riddled with woodpecker holes. Favoured trees may contain several holes, made by one species or by several. As a rule, all woodpeckers will nest as high up in a tree as practical. Tree height and the height of the nest-hole entrance, both increase with increasing woodpecker body size. Though all kinds of factors (location, tree species, availability of suitable trees, forestry practises, predation risk) influence nest-hole height, in general Great Spotted, White-backed, Black and Green Woodpeckers will nest highest up in trees. Wryneck, Middle Spotted, Syrian and Grey-headed Woodpeckers will nest at medium heights, and Lesser Spotted and Three-toed Woodpecker nests will be the lowest. Of course, there will always be exceptions. For more on nest-holes see separate page “Holes” in menu.
Roost-holes: Holes used for roosting rarely differ from nest-holes. This is because they are in fact often old nest-holes. Some species excavate specific roost-holes if there is a lack of cavities in an area. From the outside these will appear like nest-holes, though on the inside they may be less precise as those which are intended to house a brood of chicks.
Above: A typical fresh feeding site of Black Woodpecker in a pine with heart rot. Hungary (Szabolcs Kókay)
Feeding holes: Several things differentiate holes created by foraging from nesting cavities. Feeding holes do not lead to deep chambers, they almost always show pecks marks around the entrance, the hole will be irregular in shape and wood-chips are piled up below the site outside the breeding season. Feeding holes are frequently at low levels on trees whereas nest-holes are usually high up. Holes made by Black Woodpecker to get at timber dwelling ant colonies, are often long oval, sometimes almost square, slits. They can be up to 50cm long and 20cm wide.
Above: It is difficult to state for sure which species is responsible here. Black and White-backed are two candidates. Lithania (Juozas Miskinis)
Wood-chips: Woodpeckers produce wood-chips when they excavate holes or bore into timber for prey. Wood-chips are left where they fall and often accumulate below work sites. It is usually easier to distinguish wood-chips that are the result of nest-hole excavation and attribute them to species, than it is those that have resulted from foraging. The size of wood-chips is a major clue. Those that are 10cm or more are inevitably the work of Black Woodpecker. But when Green Woodpecker excavates soft wood trees such as willows, aspen and fruit trees, the wood-chips which litter the ground below can also be quite large, sometimes 7-8cm, but never as large as those of Black Woodpecker. The size of wood-chips also depends upon the structure of the wood, that is, whether it long-grained or short-grained and whether the fibres are tough or not. The quality of the wood-chips is important. It should be remembered that only Black and Great Spotted Woodpeckers regularly work on healthy, sound wood and thus clean, solid wood-chips with no signs of decay or fungi are usually the result of work done by these two species. All other European woodpeckers tend to excavate, or forage upon, soft or rotten wood, usually affected by fungi. Piles of wood dust at the base of dead stumps may indicate White-backed Woodpeckers, which often completely pulverise timber that contains beetle larvae.
Ringing: This is a series of small, more or less horizontal, holes or grooves pecked around a trunk. Ringing is sometimes referred to as “girdling”? and the peck marks called wells. It is less common amongst European woodpeckers than it is, for example, in North American species: there are no true sapsuckers in Europe. Great Spotted, Middle Spotted and Three-toed Woodpeckers ring trees for sap. Syrian, Lesser Spotted and Green Woodpeckers probably do not ring trees themselves though they do take sap from wells made by other. Black Woodpeckers do not ring trees but drink sap from large holes knocked into pines. Woodpeckers ring trees so that sap flows out from the created wells and is mostly done in spring when the sap is rising. The wells pierce the bark and cambial strata of the trunk to tap into the sap conducting routes of the tree. Sunny south-facing trunks, where sap rises first and fastest are often ringed first and most intensely. On productive trees the ringing lines will continue and encircled (girdle) the trunk. Such line may be broken or zigzagged. Several tree species are ringed though pines Pinus and limes Tilia are favourites. Intense ringing can leave wide areas of exposed bark-less trunk. In a given population of Great Spotted Woodpecker most will ring trees but only certain birds will regularly and intensely ring trees.
Above: Ringing done by Three-toed Woodpecker. Country?(?????)
Barking: Many mammals feed on and mark trees: beavers, voles, mice, squirrels, hares, rabbits, deer, even sheep and goats. Generally the marks they leave are easy to separate from those left by woodpeckers, as gnawing and individual tooth marks are left by mammals rather than peck marks. Barking refers to the marks left by deer and elk when they have eaten tree bark. I include it here because such markings can be confused with woodpecker work. Most barking takes place in spring when trees are growing and thus their sap is rising. This of course is also a period of great woodpecker activity. The mammals tear off bark in long strips (usually from bottom up) and leave large incisor marks. In winter bark is tougher and more firmly gripped onto the trunk, so the marks left by deer then are different, with clear lines or furrows left. By contrast woodpecker leave fine peck marks when stripping off bark and the bark is torn off in short sections and from top to bottom.
Tracks: In Europe only one woodpecker species, Green Woodpecker, is really terrestrial. Grey-headed is partly so, Wryneck and Black occasionally work on the floor when gathering ants, but other species rarely forage on the ground itself, though they may work on fallen logs. The only realistic situation in which to find woodpecker tracks is after snowfall. Woodpeckers only hop in mud by accident. The first thing to remember, of course, is that all except Three-toed (sic) have four toes, two pointing forwards and two back. Nine out of the ten European woodpeckers have a syndactyl formation of the toes (the second and third toes point forwards in parallel and toes one and four backwards). Three-toed Woodpecker has the first toe missing, with just toe four pointing backwards and toes two and three forwards). In the rare event that woodpecker tracks are found on the ground (in mud or snow) the quality of the tracks will depend upon the ground conditions.
Dust baths: This behaviour is not common amongst woodpeckers, probably because of the essentially arboreal lifestyle that most lead. Certainly, some species are reluctant to drop to ground level for any reason. However, as with bathing in water, it may be the case that dusting is practised by most woodpeckers but just is rarely observed. Black Woodpeckers are known to dust-bathe and the more terrestrial Wryneck and Green Woodpecker also occasionally indulges in this activity. Dust baths are often temporary and located on forest tracks. They can be recognised by wing, body and foot prints, though it is often impossible to assign these to one species.
Above: Ruts and small holes in turf can betray the work of feeding Green Woodpeckers. Sweden. (Thomas Kraft)
Droppings: Finding and identifying woodpecker droppings is one of ornithology’s great challenges. Finding a woodpecker faeces sac in a forest is harder than finding a needle in a haystack. Green Woodpecker droppings are the exception, as being terrestrial foragers and often feeding on lawns and areas with flat-cropped turf, their droppings can be conspicuous, at least for a while. They are greyish, elongated, cylindrical and composed of invertebrate remains, often dried-out ant bodies, and enclosed in a membrane. They are usually in piles at the foraging site or nearby, and resemble soggy cigarette butts. They might be confused with small mammal droppings. Green Woodpecker droppings are most often found in winter, when birds do most of their foraging on anthills.
Anvils: The anvil (sometimes termed “workshop”? or “smithy”?) is usually a natural hole, crevice or crack in a tree, log, post or even a wall, where woodpeckers wedge and process hard food items such as nuts, cones, fruit stones and large insects. Great Spotted, Syrian and possibly Green Woodpeckers use anvils. Ingvar Stenberg tells me that in Norway White-backed Woodpeckers use anvils for opening nuts (like nuthatches) but I have yet to find evidence of this in Central Europe. An important difference between anvils used by Nuthatches and those used by woodpeckers is that Nuthatch only use an anvil once, thus no piles of debris accumulate beneath it, whereas woodpeckers use favourite anvils repeatedly. Great Spotted Woodpeckers are unique in creating customised anvils to suit the food item regularly fed upon in an area. Anvils are often used for long periods hence debris, cones, nutshells, hard insect remains, accumulate beneath them. Sometimes trees with several crevices used as anvils are dotted with wedged cones and nuts and in winter take on a strange Christmas tree appearance. Cones can be wedged in anvils so well that it is sometimes hard to remove them. Conifer cones which woodpeckers have worked upon in anvils to extract the seeds, are rather crudely “beaten up”?, not systematically and neatly worked, as is done by Crossbills Loxia. Cones worked by squirrels and mice are neater. Woodpeckers break the cone scales lengthways. The stones of plums, almonds, cherries and apricots wedged in anvils are usually the result of Syrian or Great Spotted Woodpecker feeding. Cockchafer remains, too, strongly indicate these two species.
Above: Opened and discarded conifer cones below a Great Spotted Woodpecker “anvil”. Hungary (Szabolcs Kókay)
Above: Hazelnut wedged in a tree-crevice anvil by Great Spotted Woodpecker, Budapest, Hungary (Szabolcs Kókay)
Cones: Conifer cones worked on by woodpeckers, to obtain the seeds inside, are opened in a different manner from those fed on by mammals. The scales are broken lengthways and have a jagged, ruffled appearance. Piles of such cones are often found below anvils or single cones found wedged in cracks. Woodpeckers fly with cones to anvils, wedge them, tip upwards, and work them systematically, turning them around in order to open upon the scales around the whole cone. Cone scales are prised open sideways to get at the seeds. This causes the distinct ruffled appearance. Cones are not damaged on the base of the cone, where they are wedged into anvils and where the scales are also tighter. It has been calculated that it takes a Great Spotted Woodpecker around four minutes to empty a cone of its seeds and in this time the cone can be pecked some 800 times.
Above: Conifer cones wedged into a tree crevice anvil by Great Spotted Woodpecker. Budapest, Hungary (Szabolcs Kókay)
Nuts: Woodpeckers open nuts by pecking the hard shell until it shatters. Syrian and Great Spotted Woodpeckers regularly feed on nuts. They do not seem to be able to make neat holes in nutshells as rodents do. It takes numerous pecks to break open a shell, depending upon which kind of nut is being dealt with. Hazelnuts take longer to break open than, for example, walnuts. Unopened but tried nuts are dotted with peck marks rather than the gnawing marks made by the teeth of rodents. The sizes and shapes of the beak tips of birds that feed on nuts differ. Although it is not always clear these are sometimes diagnostic. The marks left on nuts by woodpeckers are dagger or chisel-shaped (vertical) whereas those left by Nuthatches Sitta europaea are crescent-shaped (horizontal). The chisel shape of woodpecker beaks is ideal for splitting nutshells as nuts split most easily along vertical fault lines. Woodpeckers have learned to exploit this. Nuts are always placed in the anvil downwards and pecked at lengthways in a line until they crack. Nuthatches never work a line to open a nut but rather chisel a round hole like a rodent does.