PREY SWITCHING AND VARIABLE FORAGING STRATEGIES OF BLACK-LEGGED KITTIWAKES AND THE EFFECT ON REPRODUCTIVE SUCCESS

Abstract

Abstract We studied the diets, foraging strategies, and reproduction of Black-legged Kittiwakes (Rissa tridactyla) during five years at two colonies within Prince William Sound, Alaska. Years with reduced occurrence of 1-year-old Pacific herring (Clupea pallasi) in kittiwake diets were associated with increased foraging trip duration, distance, and travel time at both colonies. Foraging range was consistently greater at the large, fjord colony with an annual mean trip duration of 4 hr and mean distance to the farthest feeding location of 40 km in years when 1-year-old herring dominated diets; these numbers increased to a maximum mean of 6 hr and 60 km during a year when kittiwakes consumed primarily young-of-year (YOY) herring and Pacific sand lance (Ammodytes hexapterus). Foraging trips of kittiwakes at the small, island colony averaged 2 hr and 5 km during years when 1-year-old herring dominated diets and increased when capelin (Mallotus villosus) and YOY herring and sand lance were consumed. Consequenc...