Variation in carbon and nitrogen stable isotope ratios in flight feathers of a moulting White-bellied Sunbird Cinnyris talatala

Abstract

We measured δ¹³C and δ¹⁵N isotope signatures in flight feathers of a White-bellied Sunbird to assess the value of using stable isotopes of feathers in avian dietary studies. Significant variation in δ¹³C and δ¹⁵N isotope values of flight feathers (range = 3.1%o and 2.7%o, respectively) indicated that the source of carbon (i.e. C₃ or CAM) and trophic level position shifted significantly during the flight feather moult period. Temporal dietary changes in an individual sunbird highlight the implications for interpreting avian diets using stable isotopes. However, by analysing feathers, dietary input may be interpreted at different levels if the moult process is well understood.