Available insect prey in bark patches selected by the Three-toed Woodpecker Picoides tridactylus prior to reproduction

Abstract

The diet composition of the Three-toed Woodpecker (Picoides tridactylus) before the onset of egg laying was investigated in eastern Finland. This was carried out in 1997 and 1998 by collecting bark samples from woodpecker territories in six old-growth and two burnt forest patches during the two month period preceding the start of reproductive activities . Bark samples (10 x 15 cm) were removed from the immediate vicinity of afreshly exploited area, either directly after aforaging bird left the tree or from trees recently exploited. A total of 55 bark samples were collected, from which 33 were found after direct foraging observation. Recently dead spruce comprised 89% of foraging substrates . Including adult, larva and pupa development stages, 3236 potential insect prey were collected and identified. Among them, Scolytids, or bark beetles, represented 96.9% of the insect prey. This proportion did not differ between territories, sexes and years . Some 78.5% of adult bark beetles found were classified as mature spruce forest interior specialists.