AMERICAN ROBIN NESTLINGS COMPETE BY JOCKEYING FOR POSITION

We investigated whether nestling American robins (Turdus migratorius) were capable of influencing food distribution in their nests by percei ving that certain sectors of the nest received a relatively high propo rtion of feedings and positioning themselves accordingly. Feeding obse rvations were obtained from videotape recordings taken at different st ages of the nestling period. Parents generally arrived at a predictabl e location on the nest rim and allocated proportionally more food to n estlings in the central position. The degree of nestling movement was significantly positively correlated with variation in the predictabili ty of parental arrival locations on the nest rim. Furthermore, nestlin gs moved more in broods suffering brood reduction. This suggests that when competition for food is intense and the location of parental arri val is predictable, nestlings respond by jockeying for access to the m ost favorable (i.e., central) position in the nest. We conclude that j ockeying for position by nestlings can influence the pattern of food a llocation by parents, and that hungry nestlings can improve their comp etitive standing against nestmates by moving to positions where parent s are more likely to feed them.