RESPONSES OF NESTING COMMON TERNS AND LAUGHING GULLS TO FLYOVERS BY LARGE GULLS

Disturbance can reduce productivity by disrupting nesting behavior. We examined responses of nesting Common Terns (Sterna hirundo) and Laugh ing Gulls (Larus atricilla) to frequent overhead flights by Herring (L . argentatus) and Great Black-backed (L. marinus) gulls to determine i f such flyovers may have contributed to declines in productivity. Comm on Terns and Laughing Gulls ignored most flyovers (97.9 and 99.4%, res pectively) and selectively responded to large gulls that exhibited beh aviors associated with predation. Common Terns mobbed large gulls more often than did Laughing Gulls (G = 18.3 1, P < 0.00 1), but numbers o f birds per mobbing were similar between species (Z = 1.206, df = 11, 6, P = 0.2388). We suggest that when conditions favor habituation, the presence of large gulls has minimal impact on productivity.