The influence of light intensity on the roosting times of the rook (Corvus frugilegus)

Little work has been done on the roosting behaviour of Corvidae, particularly the influence of light-intensity on its timing. This paper describes the effects of light-intensity on the roosting times of rooks (Corvus frugilegus) from a large roost during winter. Light intensity was measured and its influence on the departure of birds from the feeding grounds, arrival at the roost, entry into the roost and morning departure was found to be significant. Departure from feeding areas (and arrival at the roost) was earlier at lower light-intensities and later at higher light-intensities. Control of responsiveness to light-intensity by circadian rhythm for rooks from different feeding grounds was discussed.