Growth Rate is Negatively Correlated with Hatch Date in Black Brant

Arctic geese nest in a highly seasonal environment in which ungrazed plants reach peak nitrogen concentrations when goslings hatch (Sedinger and Raveling 1986). Grazing by geese prolongs peak nutrient concentrations but reduces food availability. This should cause nutrient availability to decline seasonally. Here, we test the hypothesis that late—hatching goslings of Black Brant (Branta bernicla nigricans) grow more slowly than those hatching early. We substracted the sizes of wild goslings from those of captive—reared goslings of the same age and regressed the differences against hatch date. Differences between wild— and captive—reared goslings for body mass, tarsus length, and culmen length were significantly negatively related to hatch date; i.e., late—hatching wild goslings were smaller than those hatching early, after accounting for age. We detected no between—year difference in gosling size, but male goslings were larger than females of the same age for all measures. Egg size was only weakly associated with size of goslings 1 mo after hatching, but we detected no effect of other brood characteristics on growth. Seasonal variation in gosling growth rate may favor early nesting in arctic geese.