Effects of season and photoperiod on food storing by black-capped chickadees,Parus atricapillus

Abstract

The effects of season and photoperiod on food storing by black-capped chickadees were examined in two experiments. Chickadees were captured in March (experiment 1) or November (experiment 2), and food storing was tested regularly in the birds' home cages. In both experiments, two groups were matched for initial level of food storing. The long-day group was then exposed to a summer photoperiod (16:8h light:dark cycle) and the short-day group to a winter photoperiod (LD 8:16h) for 2-3 months, followed by 2-3 months in identical conditions for both groups. Birds in experiment 1 stored very little at first, but those maintained on long days moulted and began to store after 6-8 weeks; the group maintained on short days eventually increased storing as well. Birds in experiment 2 began by storing about three times as much food as those in experiment 1; storing declined over time in both groups and was not affected by photoperiod. The results suggest that food storing in parids is controlled by photoperiod in a similar way to other annually varying behaviour patterns such as breeding and migration in birds.