Diurnal and individual variability in the foraging behavior of American redstarts (Setophaga ruticilla)

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Abstract
The foraging behavior of American redstarts, Setophaga ruticilla (Aves: Parulidae), was examined from dawn to dusk in the nestling phase of their breeding cycle in a northern hardwoods forest in New Hampshire, USA. Based on a sample size of nearly 3000 foraging acts, we found that redstarts hawked more and foraged lower at midday than early in the morning, coincident with a statistically significant increase in the abundance of flying insects in the lower strata of the forest at that time of day. Furthermore, individual redstarts of like sex on adjacent territories and members of mated pairs on the same territory often foraged at significantly different heights, used significantly different combinations of foraging methods, or both. A complex of factors, including the diurnal changes in insect distribution and availability, influences how birds search for and capture prey, and results in intraspecific variability which complicates studies of species-typical foraging patterns.