Seasonal and daily activity pattern in Griffon Vulture Gyps fulvus colonies on the island of Crete (Greece)

Abstract

Morning and evening counts undertaken in Griffon Vulture Gyps fulvus colonies and communal roosts revealed that their numbers fluctuated by season and time of the day. In the colonies the vultures built up high numbers during the pre-breeding and incubation periods (November–February) with maxima in December–January and dropped during the fledging and dependence periods (July–October) with minima in June–July. On the contrary griffons started to use communal roosts during the chick-rearing period (March–June) while their numbers peaked when the young fledged (June–August). Daily use of colonies exhibited a bimodal pattern that was most pronounced in the pre-breeding period. Population size should be assessed by conducting morning counts starting at dawn in all active colonies and communal roosts during November–February.