Morphology, body condition and survival of Great Black-backed Gull (Larus marinus) chicks raised in broods of different size in southern New Brunswick, Canada, were compared. The relationship between age and body size measurements taken from 68 chicks, between 0 and 56 days of age, was analyzed. The logistic model provided the best fit of the morphological measurements (culmen, tarsus, and wing) to age, and the Gompertz model provided the best fit of body mass to age. These models were used to make linear transformations of body size variables that were used in subsequent analysis. There was no difference in the morphology of chicks raised in broods of different size. The first principle component (PC1) from the correlation matrix of the three transformed morphological variables was used as covariate in subsequent analysis to remove variation in body mass that was caused by differences in body size. All chicks were in the same relative body condition at hatch. Body condition of chicks raised in one-chick broods improved with age, that of chicks raised in two-chick broods did not change, but body condition of chicks from broods of three declined with age. In contrast, chicks from larger broods were more likely to survive the nestling period. Although body condition was lower in chicks from larger broods, other factors unrelated to body condition, such as differences in parental quality, led to higher survival for chicks in broods of three.
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Vol. 39 • No. sp1