Habitat Type is Related to Nest Mass and Fledging Success of Arctic Warblers

Abstract

Abstract Relatively little is known about Arctic Warblers (Phylloscopus borealis) that breed in central Alaska. We monitored Arctic Warbler populations in two adjacent but distinct habitat types in central Alaska (high elevation, ‘open shrub’ and lower elevation, ‘dense shrub’). We collected 95 nests over three breeding seasons to learn more about nest-building behavior, nest mass, composition, fledging success, and nest parasites. Females were the sole builders of ground nests, which were primarily comprised of moss, grass, and a lining of moose (Alces alces) hair. Dry weight of nests was ∼20 g, but differed up to ∼3-fold within each habitat type each season. Nests from open shrub habitats were more massive and contained less moose hair lining than nests in dense shrub. Open shrub nests fledged more young during the most productive breeding season. We report the first record of the parasitic blowfly Protocalliphora tundrae in Arctic Warbler nests and for Alaska. Blowfly parasitism (55% of nests with hatc...