Factors affecting kleptoparasitism by gulls in a multi-species seabird colony

GARCÍA GO, M FAVERO & AI VASALLO

THE CONDOR

COOPER ORNITHOLOGICAL SOC

Año: 2010 vol. 112 p. 521 - 529

0010-5422

Kleptoparasitism is defined as the stealing by one animal of food that has been caught by another. This behavior is a well known foraging tactic used opportunistically by many seabird species. Our study describes qualitatively and quantitatively kleptoparasitic behavior in a tern-gull system, and compares the effect of prey quality (prey type and size) and environmental conditions (tidal stages, wind direction and intensity) triggering such behavior. The rate of kleptoparasitism by Kelp Gulls (Larus dominicanus) was higher on Royal (Thalasseus maximus) than on Cayenne Terns (T. sandvicensis eurygnatha). However, the percentage of successful attacks was similar on both species (ca. 42%). We used an information-theoretic approach to determine relative importance of prey quality and environmental conditions in triggering kleptoparasitism. We found that more valuable prey triggered kleptoparasitism whereas the environmental conditions included in the models didn’t significantly affect the rate of such behavior. Our study shows the importance of prey quality in triggering kleptoparasitism, and how this behavior can remove an important portion of food brought to the tern colony.