Abstract
The sleep–wake patterns and nocturnal activity of diurnal birds have been little studied. Here, we analysed, by chance, those behaviours for free-living Eurasian Blue Tits ( Cyanistes caeruleus , Linnaeus, 1758) roosting in nest boxes equipped with motion sensor-triggered Internet Protocol (IP) cameras. By monitoring individual birds over six sessions for more than one hundred nights each session, we found repetitive activity patterns during the night as well as a correlation between daylength and roosting times. Using the same method, we found the roosting behaviour of Eurasian Blue Tits ( Cyanistes caeruleus , Linnaeus, 1758) to be comparable to that of Great Tits ( Parus major, Linnaeus, 1758) and Common Starlings ( Sturnus vulgaris , Linnaeus, 1758) in nest boxes in the same structure. These data, which we showed can be collected relatively easily and inexpensively, suggest that in rural areas the sleep–wake behaviours of free-living birds are mainly determined by the circadian rhythm associated with natural light.