title: Divergence in foraging behavior of foliage-gleaning birds of Canadian and Russian boreal forests.
abstract: We compared foraging behavior of foliage-gleaning birds of the boreal forest of two Palaearctic (central Siberia and European Russia) and two Nearctic (Mackenzie and Ontario, Canada) sites. Using discriminant function analysis on paired sites we were able to distinguish foliage-gleaning species from the Nearctic and Palaearctic with few misclassifications. The two variables that most consistently distinguished species of the two avifaunas were the percentage use of conifer foliage and the percentage use of all foliage. Nearctic foliage-gleaner assemblages had more species that foraged predominantly from coniferous foliage and displayed a greater tendency to forage from foliage, both coniferous and broad-leafed, rather than twigs, branches, or other substrates. The greater specialization on foliage and, in particular, conifer foliage by New World canopy foliage insectivores is consistent with previously proposed hypotheses regarding the role of Pleistocene vegetation history on ecological generalization of Eurasian species. Boreal forest, composed primarily of spruce and pine, was widespread in eastern North America, whereas pockets of forest were scattered in Eurasia (mostly the mountains of southern Europe and Asia). This may have affected the populations of birds directly or indirectly through reduction in the diversity and abundance of defoliating outbreak insects. Loss of habitat and resources may have selected against ecological specialization on these habitats and resources.
authors.affiliation: Smithsonian Migratory Center, National Zoological Park, Washington, DC 20008, USA e-mail: antbird@erols.com, , , , , , US.
authors.forename: Russell
authors.initials: R
authors.lastname: Greenberg
authors.affiliation: Department of Zoology, Ohio State University, Columbus, OH 43210, USA, , , , , , US.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Pravosudov
authors.affiliation: Smithsonian Migratory Center, National Zoological Park, Washington, DC 20008, USA e-mail: antbird@erols.com, , , , , , US.
authors.forename: John
authors.initials: J
authors.lastname: Sterling
authors.affiliation: 4075 Monticello Blvd., Apt. 305, Cleveland Heights, OH 44121, USA, , , , , , US.
authors.forename: Anna
authors.initials: A
authors.lastname: Kozlenko
authors.affiliation: State Darwin 57, Vasilova, Moscow 117292, Russia, , , , , , RU.
authors.forename: Vitally
authors.initials: V
authors.lastname: Kontorschikov
keywords: Historical; Key words Ecological convergence; Outbreak insects; Pleistocene glaciations; Warblers