Age Differences in Foraging Behavior of the American Robin (Turdus Migratorius)

Abstract

Comparison of feeding behavior of adult and juvenile American robins (Turdus migratorius) revealed significant differences in several measures of feeding efficiency and success. Adult robins captured larger food items, made more captures per unit time, took fewer steps, and made fewer unsuccessful attempts. Juveniles took 136% as long to capture each food item and required 161 % as many steps as adults, obtaining 25% less food per unit time. During the 10 weeks of the study foraging efficiency fluctuated, apparently reflecting differences in food availability, and we were unable to detect any improvement in efficiency of juveniles relative to adults during the course of the study. Three spot-classes of juvenile plumage were defined, and are believed to reflect slight average age differences, but no difference in foraging efficiency could be detected between the classes, indicating that between about 3 and 5 months of age, improvement must be subtle. This documentation of age differences between adult and juveniles that have been independent 1 to 4 months points to the importance of skill acquisition in foraging behavior in altricial birds.