Meeting Abstract
Understanding the movement patterns of vagile species is critical to answering evolutionary, conservation and mechanistic questions. Tracking technology has improved knowledge of animal movements, but is still limited in its applicability. Stable hydrogen isotope (δ2H) signatures in feathers are increasingly used to determine the movement patterns of bird migrations and irruptions. We used the stable isotope approach to investigate the relative movement patterns of different vocal types of red crossbill (Loxia curvirostra) in western North America. We collected ‘worn’ feathers in late summer from crossbills of three vocal types: Type 5 (Wyoming), Type 3 (Washington), and Type 2 (Oregon). Worn feathers, grown the previous year, can be used to examine variation in habitat use during molt one-year prior; the inter-individual variation in worn feather isotope signatures should correlate positively with the diversity of habitat types used by the different crossbill types. Feather samples were analyzed at the UC Davis Stable Isotope Facility. We found significant between-type variation in inter-individual variability in feather δ2H (Kruskal-Wallis chi-squared=8.5, p=0.014). The isotope signature variation was larger in feathers collected from Type 2 crossbills (δVSMOW range of 65.2 units) compared to both Type 5 (δVSMOW unit range of 49.8 units) and Type 3 crossbills (δVSMOW unit range of 19.6 units). This is consistent with the different individual Type 2 crossbills having molted the previous year in a greater diversity of locations or habitats than the Type 5 or Type 3 birds. These results are consistent with the interpretation that nomadic crossbill types may differ in their degree of nomadism, and these differences in movement may be related to habitat selection and diet choice.
