Brood Size and Chick Position as Factors Influencing Feeding Frequency, Growth, and Survival of Nestling Double-crested Cormorants, Phalacrocorax auritus
Аннотация:This study examines brood size and chick position in the hatching sequence as factors influencing the feeding frequency, growth and mortality of 34 Double-crested Cormorant chicks (Phalacrocorax auritus) constituting 13 broods of a treenesting colony at Iles de la Madeleine, Québec.Growth curves of chicks weighed approximately every three days were fitted to the Gompertz equation.Although the mean final weight, the number of feeding periods and number of daily foraging trips tended to increase with increasing brood size and declining average growth rate and individual feeding frequency, those relationships were not statistically significant.This suggests that breeding Double-crested Cormorants of that colony adjust the amount of food they bring to the nest from each foraging trip according to brood size, and that chicks are fed the same amount of food irrespective of brood size.Final weights, growth rates, meal size and feeding frequency of individual chicks did not seem to vary as a function of their position in the hatching sequence.There was not a higher mortality in chicks hatched last in a brood than in those hatched earlier, but all nestlings that died did so within a few days after hatching.Consequently, there is no evidence that a chick hatched last in a brood survives less well than those hatched earlier.
