Chick provisioning by common terns in the southern Gulf of Maine, USA

We examined chick provisioning by common terns (Sterna hirundo) in relation to hatching order, chick stage, and weather on Stratton Island, Maine, U.S .A., during the summer of 1997. Provisioning rates, recorded at 10 nests du ring 30-min observation sessions (n = 256), were calculated for first-, sec ond-, and third-hatched chicks in three age-classes (1-5, 6-10, and 11-15 d ays). Mean provisioning rates did not differ significantly with hatching or der of chicks. However, a trend toward differential provisioning was eviden t during the earliest chick stage. Mean provisioning rates increased signif icantly from age-classs 1 to 2 and decreased significantly from age-classes 2 to 3. Weather had no significant effects on provisioning rates, owing to the unusually mild and consistent conditions. These results indicate that during the earliest chick stage, older siblings in a brood may have an adva ntage in obtaining food, even when weather conditions are highly favorable for provisioning chicks.