Effects of Nestling Age and Brood Size on Nestling Care in the Bachman's Sparrow (Aimophila aestivalis)

Abstract

Effects of nestling age and brood size on parental food delivery and brood attention time were studied in the Bachman's sparrow (Aimophila aestivalis) in central Arkansas [USA] from 1983-1985. Nestlings received an increase in food mass with age because both parents increased the size of foods they delivered and because females increased the number of feeding trips and food items delivered. Males delivered a greater percentage of lepidopteran larvae to 0-2 day-old nestlings than to older nestlings. Nestling attentive time for both parents decreased with nestling age. Nestlings of large broods received approximately the same food mass as small brood nestlings because both parents increased the number of feeding trips and food items delivered. Brood size had no effect on the types of foods fed to nestlings. Small brood nestlings received more attentive time than large brood nestlings. Although females spent more time at the nest than males, they delivered roughly the same amount of food.