Effects of artificial light and latitude on the dawn foraging activity of Great Tits (Parus major) during winter in northern Europe

Abstract

Cover photo: Male Great Tit Parus major. Photo: Bjørn Aksel Bjerke. Recently, there has been increasing interest in the ecological consequences of artificial light on wildlife. At northern latitudes, winter is characterized by short days and low temperatures. Under these conditions, resident birds need to consume more food in a shorter time to sustain their metabolism and maintain body temperature. Access to artificial light may prolong foraging opportunities for resident birds during winter. Here, we used a field experiment to test whether Great Tits Parus major benefit from artificial light to start foraging before sunrise. Further, we conducted a meta-analysis to test if onset of foraging was correlated with latitude in the Great Tit. A feeding station with artificial light was placed in a forest area in Ås, SE Norway, at nearly 60° north. A camera was placed in front of the feeding station to record daily activity of the Great Tit in December and February. In December, Great Tits started foraging earlier relative to sunrise when artificial light was available. In February, Great Tits were not stimulated by artificial light to start foraging before sunrise. The onset of foraging in Great Tits was also correlated with latitude. At the northernmost location, Great Tits started foraging several hours before sunrise, whereas at the southernmost location, Great Tits started foraging only a few minutes before sunrise. The results suggest that resident Great Tits may utilize artificial light to prolong their foraging activity during midwinter, and that onset of foraging is advanced relative to sunrise with decreasing daylength further north. Our findings contribute to the understanding of how short days during northern winters can limit foraging activity in resident birds.