Foraging ecology of two bark foraging passerine birds in an old-growth temperate forest

Abstrakti

This study deals with the foraging ecology of two bark foraging birds Nuthatch (Sitta europaea) and Eurasian Treecreeper (Certhia familiaris) in an old-growth temperate montane forest (Mala Fatra Mts., Western Carpathians, Slovakia). Tree species prefer-ences and foraging behaviour were studied during four breeding periods. Both species showed similar annual dynamics in tree species preference; Beech (Fagus sylvatica) was avoided whereas Norway Spruce (Picea abies) and Sycamore (Acer pseudoplatanus) were preferred. Both bird species showed clear year-to-year variation in foraging patterns on Beech, but not for other tree species. In all three tree species the trunk itself and the larger branches were the most preferred foraging substrates. The Treecreeper over-uti-lized the trunks of Beech, Spruce and Fir (Abies alba) but no such differences between Treecreeper and Nuthatch were found for either Sycamore or snags. Overall, Nuthatch tends to be a broad-niched forager employing a greater variety of foraging techniques (mainly the glean and probe strategy) than Treecreeper (mostly glean and occasionally flutter chase). According to the results of this study, single-year studies might give an in-accurate picture of tree species preference by bark foraging bird species. Tree species composition may play an important role in habitat quality for both Nuthatch and Tree-creeper and have implications for forest management.