VARIATIONS IN GROWTH OF ROSEATE TERN CHICKS

We measured growth parameters of Roseate Tern (Sterna dougallii) chick s at two contrasting colonies: Bird Island, Massachusetts, and Falkner Island, Connecticut, from 1987 through 1990. Differences in growth pa rameters among individual chicks are used to explore differences in pa rental performance, whereas differences in average growth parameters a mong colonies and years are used to explore differences in average env ironmental conditions. Chicks were marked at hatching and weighed at o ne- or two-day intervals. For each chick that survived to hedging, we calculated two measures of growth: linear growth rate and asymptotic m ass. There were no significant differences between growth parameters o f first-hatched chicks in broods of one and two. Both measures of grow th were significantly fewer and more variable for second-hatched chick s than for first-hatched chicks. Both measures were significantly posi tively related to egg mass and negatively related to hatch date. After controlling for these variables, differences between colonies and amo ng years were relatively small and inconsistent. Mean survival of seco nd-hatched chicks was positively correlated with the mean growth rate of survivors across colonies and years. These findings are consistent with a general hypothesis that growth of chicks reflects individual pa rental performance and parental quality.