Construction and materials of common crossbill nests collected in shimokita, aomori prefecture

Abstract

We investigated the structure and materials of two nests of the Common Crossbill Loxia curvirostra collected in Shimokita Peninsula, Aomori Prefecture, Japan. The nest bowl was constructed of pine twigs with bark, shredded bark, wood-chips, other twigs, chemical fiber yarns, staple fibers, grasses, pine needles, feathers, rhizomorphs, animal hairs and fishing line. These materials were utilized in different manner in the exterior and interior nest bowl. Pine twigs with bark were used only for the most exterior portion, whereas the middle and interior parts consisted mainly of shredded bark of Cryptomeria japonica. Harder objects, such as twigs, wood chips and flexible fishing line, used for the middle part, served as a framework to produce a space between fibers and strings, creating a spongy layer of air. The area around the interior nest bowl was composed of thinner bark strings than the middle and outer nest bowl. Chemical fiber yarn, feathers and animal hairs were also found around the interior bowl.