Territoriality and Behavioral Correlates of Reproductive Success of Great Black-Backed Gulls

Abstract

Territorial characteristics and behavioral correlates of reproductive success were examined in a population of Great Black-backed Gulls (Larus marinus). Territories were defended from the preincubation through the postfledging periods, and 53% of the territories under observation increased in size following chick hatching. Territorial adults displayed significantly more high-level agonistic behavior toward non-neighboring intruders than they did toward neighboring intruders. Most agonistic interactions, however, occurred between adjacent territorial neighbors, and only small segments of territorial boundaries were consistent sites of intense agonistic interaction. Chick mortality was not related to percent vegetative cover, nearest-neighbor distance, territory size, or intrusion pressure. Chick mortality was positively correlated, however, with both the number of contiguous territories and the frequency of agonistic interactions of male gulls. Both post-hatch frequencies of neighbor intrusions and intrusions by non-neighboring conspecifics were positively correlated with the number of contiguous territories, but were not related to territory size. Finally, the time that adults left their territories abandoned during the posthatch period was negatively correlated with the frequency of intrusions (by both neighboring and non-neighboring conspecifics) and positively correlated with the number of chicks fledged.