Research on Defence Behaviour in a Common Gull (Larus Canus) Colony during Breeding

Abstract

The research was carried out on the Didžioji Island, Lake Kretuonas (eastern Lithuania). A stuffed Raven (Corvus corax) was displayed in a Common Gull (Larus canus) colony during different breeding stages and attacks on the stuffed Raven made by Common Gulls flying higher and lower than 1 m above it as well as attacks of a direct contact were recorded. The stuffed Raven was demonstrated outside the colony, in the periphery of the colony, and in the centre of it. The most intensive defence behaviour was demonstrated during the second half of the breeding cycle and during nestling hatching. Especially frequent direct attacks, made by several dozen of birds, were observed in the centre. Stages of the breeding cycle in the centre and in the periphery of a Common Gull colony are different, which affects defence behaviour in the birds. During later stages of the breeding cycle offsprings of the pairs that have bred in the centre of the colony can be defended by a kind of a buffer zone, the periphery where breed...