Investigating Deuterium Depletion in American Kestrel (Falco sparverius) Nestlings Using Growth Rates

Animal tissues should reflect the local precipitation isotope ratios of hydrogen ( ¹ H) and Deuterium ( ² H, or “D”) (δD). We found that nestling American Kestrels had relatively low δD values in their claws (δD _c ) compared to adults from the same area. Growth rates could possibly influence uptake of hydrogen isotopes during tissue development. To test this hypothesis, we examined the δD _c of nestlings with different growth rates. We predicted that fast growing nestlings would show lower δD _c due to increased uptake of ¹ H, while slow growing nestlings would show higher δD _c . We collected small claw clipping samples and morphometrics from birds ranging from 21 to 25 days old. Claw samples were washed, weighed, pyrolyzed through gas chromatography and analyzed by mass spectrometer to obtain δD _c . Results from this project will show if growth rates can explain the differences in δD _c between adult and nestling American Kestrels.