The timing of early morning feeding by tits

Abstract

Environmental factors correlating with the time of first morning arrival at a feeding station were investigated for Blue Tits Parus caeruleus, Great Tits P. major and Coal Tits P. ater over two years. Year-round, the arrival times (related to both sunrise and civil twilight) correlated primarily with daylength and cloud cover, but this disguised marked seasonal variation in the environmental correlates. In winter, daylength remained the primary positive correlate but was of little importance in spring and summer. In autumn, daylength was negatively correlated with arrival time. Temperature correlated with arrival time mainly in spring, early summer and autumn; only male Great Tits' arrival correlated with temperature in winter. Female Blue Tits and Coal Tits arrived first, followed in order by male Great Tits, male Blue Tits and female Great Tits. These changes in foraging behaviour are interpreted as responses to seasonal changes in energy demand and the effects of interspecific competition when there are either environmental constraints on foraging time and profitability as in winter, or conflicts with other essential behaviours as in spring.