| Summary: | The Black-legged Kittiwake Rissa tridactyla population is declining throughout its North Atlantic range. In Norway, the species is classified as Endangered on the Norwegian Red List. Studies of diet are one important requirement for effective management of any species. Because it is easier to sample, chick diet has often been considered a proxy for adult diet in many seabird studies, but the optimal-foraging theory predicts that this may not be accurate. This study found, however, contrary to the theory, no significant differences in either prey composition or prey size in the diets of adult kittiwakes and their chicks in a north Norwegian colony during the 2012 breeding season. The main prey for both adults and chicks was capelin Mallotus villosus. Fewer samples were obtained from birds without chicks than from birds with chicks; this was considered to be a consequence of the former digesting their meals at sea before returning to the colony. Differences in diet of surface feeders can, however, be both seasonal and geographically dependent, and a similar study on kittiwakes in a different location or in a different breeding season may show a quality difference in diet between adults and chicks.
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