Exploring sources of (co-)variation in timing and total daily feeder visits in a wild population of black-capped chickadees.

Abstract

The timing and amount of foraging in birds are shaped by many of the same extrinsic factors, including temperature and daylength, as well as intrinsic factors, such as sex and age. Here, we investigate co-variation between these traits. We observed a population of 143 individually marked black-capped chickadees (Poecile atricapillus) over a 90 day period during the winter. For each day, we recorded the time an individual began and ended feeder use relative to sunrise/sunset, and the total number of feeder visits. Within-individuals, both earlier first feeder visit and later last feeder visit were associated with higher total daily feeder visits but lower feeding rates. Individuals also differed consistently in the timing of first and last feeder visits, and individuals that consistently started feeder use earlier in the day ended feeder use later and had higher total daily feeder visits compared with those that started later, but had no difference in feeding rate. Our study demonstrates that variation in the timing of foraging can have important consequences for energy acquisition at both the within- and among-individual levels.