Abstract
This study examined differences in response to humans approaching the nest for incubating herring and great black–backed gulls with varying amounts of prior exposure to humans. Gulls nesting in frequently disturbed areas sat more tenaciously, responded more slowly, and returned to the nest more quickly following the intruder's retreat, than birds nesting in less disturbed areas. The species differed in their responses in different areas. Stage of incubation had little effect, except that late in incubation herring gulls returned to the nest more quickly. Weather variables affected responses of great black-backed gulls. For both species the behaviours we scored when the experimenter approached the nest were correlated, as were those following departure, but there was no correlation between these two sets of responses. Our study provides evidence on the relationships among components of an alarm and escape response, and provides a measure of influence of human disturbance for two species of gulls.