Junco hyemalis Bone Microstructure

Migration is the primary strategy that temperate birds use to avoid overwintering under harsh conditions. As a consequence, migratory birds have evolved specific morphological features in their wings and skeleton. However, in addition to varying in overall shape and size, bone can also change at the microstructural level by, for example, increasing its thickness. Such changes are critical to preventing fracture and damage under repeated loading (fatigue), yet it is not known whether migratory behaviour influences bone microstructure. To address this gap in the literature, we performed micro-computed tomography on skeletons of resident and migrant subspecies of the Dark-eyed Junco Junco hyemalis. We investigated the differences in the major wing bone, the humerus, and the major leg bone, the femur. In each bone, we studied the microarchitecture of the two types of bone tissue: cortical bone, the thick outer layer of bone; and trabecular bone, which is the porous network of bone tissue at...