| Abstract: | We experimentally studied the aggressive antipredator behavior of black skimmers Rynchops niger nesting in a salt marsh and sandy beach with the use of a live herring gull Larus argentatus. Although there were no significant habitat differences in vegetation cover, distance from the edge of the colony, or nesting density, skimmers nesting in salt marshes were more aggressive toward the herring gull than were those nesting on the beach. Aggression increased during the first three minutes of the test, and decreased slightly thereafter. Aggression levels were highest when the gull moved compared to when it was stationary. Skimmers made few responses when a person was present with the gull, but aggression increased dramatically when only the gull remained. Our results suggest skimmers may engage in more aggressive behavior in defense of their nests than previously thought, particularly when exposed to a predator that actually takes eggs and chicks. Further, we suggest that conclusions about antipredator behavior drawn only from studies of interactions with people may need further amplification. © 1992 Wiley-Liss, Inc. |
