Some sources of variation in the elemental composition of Bald Eagle feathers

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Abstract
Concentrations of Br, Mn, Na, Al, and Cl were measured in back and tail feathers and concentrations of Mg and Ca were measured in tail feathers of wild and captive Bald Eagles (Haliaeetus leucocephalus) using instrumental neutron activation analysis. Feather chemistry of four eagles sampled over 3 years showed considerable annual variation. The profiles of tail feathers, however, appeared distinct for each individual. The mineral profiles of feathers of wild nestlings were usually significantly variable among years. A sex difference was evident for Cl, and perhaps Br and Na, in back feathers of nestlings. Mn and Al concentrations were significantly influenced by the species of prey on which the eaglets had fed. Variation attributable to sex likely has a physiological basis, while much of annual variation can likely be explained by diet.