Influence of Feather Selection and Sampling Protocol on Interpretations of Hawaiian Petrel (Pterodroma sandwichensis) Nonbreeding Season Foraging Habits from Stable Isotope Analysis
Isotope data from Hawaiian Petrel (Pterodroma sandwichensis) primaries P1 and P6 were compared to determine whether foraging habits change between the beginning and middle of the nonbreeding season. P6 data did not differ between samples derived from a longitudinal and a minimally invasive protocol and point samples taken from the feather bases. While P6 delta C-13 increased longitudinally, no delta N-15 longitudinal trends emerged, yet inter-individual delta N-15 variability was high. P6 delta C-13 data suggest that Hawaiian Petrels molt at low latitudes. Among colonies, all of which are located in the Hawaiian Islands, USA, low P6 delta N-15 values for Maui birds relative to Hawaii and Lanai birds reflect foraging segregation and differential utilization of N-15-enriched oceanic regions. For the Hawaiian Petrel, the isotopic similarity between P1 and P6 indicates that analogous ecological interpretations can be drawn from these feathers, and similar foraging habits persist from the beginning to middle of the nonbreeding season. Prolonged inter-colony foraging segregation may facilitate coexistence of colonies and, together with high intra-colony foraging diversity, may reduce extinction risk for the endangered Hawaiian Petrel.
