Food allocation among nestlings has a strong influence on parental fitness. Maximizing fledging success in a favorable environment requires food distribution based on offspring need signals. However, food limitation, differences among individual nestlings in their quality, or variation in the costs of rearing different young may result in preferential allocation of food by parents. If signals of nestling quality or need change in meaning with age, parents are expected to adjust their feeding rules to those changes. We examined food allocation in broods of Collared Flycatchers (Ficedula albicollis), a sexually size-monomorphic passerine. In a multivariate analysis, we investigated the role of sex, size, condition, position, and begging intensity in two nestling ages. Size, condition, and sex of nestlings did not affect parental decisions. Begging intensity and nestling position, however, had a role in food allocation in both age categories. Both parents preferred the more intensely begging nestlings. Males did not show clear position preference in the “young” age category, but had preferred positions with older nestlings. Female position preference was observed in both age categories. Preferred positions of male and female parents differed; still, we observed overall position preference.
Asignación de Alimentos en Nidadas de Ficedula albicollis: ¿Cambian las Reglas con la Edad de los Pichones?