Title

Growth and Brood Reduction of Mid-Atlantic Coast Ospreys

Publication Date

1991

Journal or Book Title

AUK

Abstract

Ospreys (Pandion haliaetus) exhibit both large geographic differences in growth rate and variable levels of brood reduction, which are assumed dependent on local prey abundance. We examined Ospreys nesting along the mid-Atlantic coast to determine how growth rate and brood reduction were influenced by an abundant, available prey base. Growth rate was substantially higher than previously reported and best described by a logistic growth curve (k = 0.173). We found little or no difference in growth related to year, to brood size, or in broods with and without nestling loss. Brood reduction occurred in this area, despite an apparently ample prey base, and was more common in larger broods. Higher incidence of brood reduction in large broods was a function of larger disparities in within-brood nestling size, probably caused by inadequate food provisioning by males. We believe large intercolony differences in Osprey growth are primarily a function of local food abundance and availability, whereas intracolony variation--reflected in higher rates of brood reduction--may be a function of a male's ability, experience, or motivation to provide food to nestlings.

Volume

108

Issue

2

Pages

363-370

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