Thursday, 13 September 2007

Woodpecker signs: 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 (see photo) that contains beetle larvae. This photo shows a typical feeding site of White-backed Woodpecker. A finely shaved rotting stump, from top to ground level and with wood-chips but also powder-like debris. Bükk Hills, Hungary (Szabolcs Kókay)

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