Document: JEF-3-51-19

Relationships among breeding latitude, timing of migration, and wintering latitude in Wilson's Warblers as revealed by hydrogen stable-isotope ratios.

KELLY, J.F.* ¹, V.A.ATUDOREI ², Z.D.SHARP ² and D.M.FINCH ¹

Rocky Mountain Research Station, Albuquerque, NM 87106 ¹
University of New Mexico, Albuquerque NM 78131 ²

Abstract:
Our ability to track migrant songbirds from their breeding areas through migration to their wintering grounds is limited. It has been shown that stable hydrogen isotope ratios can be used as a geographic marker of breeding latitude that is carried with songbirds through migration to wintering areas. We used a continuous-flow high-temperature pyrolysis elemental analyzer (Finnigan TC-EA) interfaced with a Delta Plus XL mass spectrometer to measure the hydrogen isotope ratio of bird feathers. We analyzed the stable hydrogen isotope ratios in the feathers of Wilson's Warblers (Wilsonia pusilla) from the breeding season, fall migration, spring migration, and winter. We found that for breeding Wilson's Warblers, the latitude where the feather was collected was significantly negatively related to hydrogen isotope ratio (R²= 0.55, P<0.0001, n = 56). We also found a significant positive relationship between hydrogen isotope ratio and timing of capture in the Middle Rio Grande Valley, NM during fall migration (R²= 0.27, P=0.0007, n = 39), but no such relationship during spring migration. Finally, preliminary results suggest that hydrogen isotope ratio on the wintering range is positively related to latitude (R² = 0.80, P=0.0004, n = 10). These results suggest that Wilson's Warblers that breed in western North America are leapfrog migrants. That is, individuals from the northern portion of the breeding range begin migration earlier and travel further south than individuals breeding at more southern latitudes.

Keywords: Avian Migration, Stable Isotopes, Tracking Animal Movement

This abstract is being presented at: 9:45 AM in session:
Oral Session #3: Avian Ecology.