Nocturnal behaviour of ring-billed gulls during the early incubation period

Abstract

Observations of ring-billed gull behaviour on Mugg's Island, Toronto Harbour, in 1978 demonstrated that behaviour at night was much less aggressive and more sexual than during the day. The differences were probably caused by reduced visual discrimination and increased fear within the gulls at night. The evolutionary causes and consequences of the behavioural differences are discussed with reference to the temporal and spatial patterns of nesting in ring-bills.