Declining thick-billed murre Uria lomvia colonies experience higher gull predation rates: an inter-colony comparison

摘要: Abstract Avian predators of colonial-nesting seabirds preferentially attack individuals nesting alone or on the edge groups, apparently because they can forage without being struck by defending neighbours. If densities colonial declined, are predicted to have fewer foraging constraints and consequently a greater impact seabird reproduction. Thus, avian predation could prevent recovery populations once sources adult mortality been removed. To test these predictions, glaucous gull Larus hyperboreus rates, mode selection murre nest-site at an expanding thick-billed Uria lomvia colony (Coats Island, Canada) were compared with those declining colonies in Northwest Greenland (Timmiak, Kingittoq). At Coats most cliff ledges densely occupied breeding murres so that gulls not extensively foot. Gulls relied wind when (>10 km/h), which enhanced their aerial maneuverability enabled them reach nest sites narrow poorly defended. In contrast, Kingittoq foraged foot regardless conditions broad supported small groups murres. This resulted higher rates low speeds Kingittoq. Timmiak, had experienced greatest population declines, nested high crevices inaccessible gulls. It was concluded lower reduce risk injury for during this increases speeds. These findings suggest declines result from human-induced (e.g. over-harvest) increase reproduction potentially, slow colonies.