Body-mass variation in breeding Northern Wheatears: a field experiment with supplementary food

Abstract:

Changes in body mass of breeding Northern Wheatears, Oenanthe oenanthe, on the island of Öland, south Sweden, were monitored during 1985-1987 in the context of a food provisioning experiment. Individuals were weighed periodically by attracting them to feeders which were placed on electronic digital balances. Rations of 7 g of mealworms per visiting individual were offered daily on certain territories (in 1987, some individuals were offered rations of 4.5 and 9 g). Unprovisioned birds were captured and weighed during the study. Males maintained constant body masses throughout the season. Females increased in mass up to laying, maintained relatively large masses during incubation, and dropped in mass by 14% during the first week after the young hatched. Mass then attained constant levels until the time of offspring independence. There was a positive correlation between brood size and the …

Año de publicación:

1989

Keywords:

Fuente:

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