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

We measured delta C-13 and delta N-15 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 delta C-13 and delta N-15 isotope values of flight feathers (range = 3.1 parts per thousand and 2.7 parts per thousand, respectively) indicated that the source of carbon (i.e. C-3 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.