Thursday, 13 September 2007
Woodpecker signs: 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. The photo here shows opened and discarded conifer cones below a Great Spotted Woodpecker anvil in Hungary (Szabolcs Kókay).