Individual foraging strategies of kleptoparasitic Roseate Terns

We describe the kleptoparasitic behavior of ten adult Roseate Terns (Sterna dougallii) breeding at a colony at Falkner Island, Connecticut, USA between 1995 and 1998. These birds were considered habitual kleptoparasites because they stole fish repeatedly from other terns in every year they were observed at the site. No other breeding individuals were observed attempting to steal fish during our study. Kleptoparasitic techniques included aerial piracy, ground-based attacks, and deceptive behavior, but with one exception, each individual used one method exclusively. Success varied among individuals, but overall, kleptoparasites obtained prey at a significantly higher rate than did 'honest' foragers. Eight of the ten kleptoparasites were females, suggesting a sex-biased tendency in Roseate Terns to engage in this behavior. Our observations indicate that kleptoparasitism by Roseate Terns is a specialized behavior, used regularly by only a few individuals at this breeding colony. This conclusion is consistent with a recent theoretical prediction regarding kleptoparasitism in birds.