Neutron activation analysis of bald eagle feathers: analytical precision and sources of sampling variation

Abstract

Instrumental neutron activation analysis was used to investigate the feather chemistry of wild and captive bald eagles (Haliaeetus leucocephalus). This paper documents variation that may be attributable to method of feather collection, laundering of samples, and precision of the analysis, as well as the variability within and among feathers from different locations on the body of individual birds. For most samples, reliable estimates could be made of the concentrations of bromine, magnesium. manganese, sodium, vanadium, aluminum, chlorine, calcium, and sulphur. Iodine and copper were detected but could not be measured precisely. There were highly significant patterns of variation along the length of a single feather for most chemical elements. The vane and calamus portions of feathers differed in chemical composition and the concentrations of the elements in the two parts were not correlated. Feathers belonging to the same molt but collected several months apart had similar chemical profiles. Variation within an individual feather and among feathers from different parts of the body necessitates rigorous consistency in the method of sampling feathers. Possible explanations for the observed patterns of elemental composition are discussed.