The influence of food on time budgets and timing of breeding of the Dunnock Prunella modularis

In two years, we provided some female Dunnocks with extra food from January through to July. In one year fed females bred ten days earlier than controls and in another year they bred 22 days earlier, but in neither year did they lay larger clutches. Matched comparisons of the same females on the same territories, who had food in one year but not in the other, showed the same effects. Within both feeder and control females, the earliest breeders were those which had spent more time perching in late winter. Perching time may be a good measure of the time an individual has available above that needed for self maintenance. Therefore females who spent more time perching may have been those first able to cross the threshold of extra time needed for the start of breeding activities.