Low productivity of bald eagles on Prince of Wales Island, southeast Alaska

Investigated reproductive success of Bald Eagles (Haliaeetus leucocephalus) on Prince of Wales Island, Alaska from 1991-93. Productivity (0.13 young produced per occupied territory) was the lowest recorded for the species throughout its geographic range. Productivity was not significantly different among different habitats including remote roadless areas vs. roaded and logged areas, which suggested that habitat alterations were not the cause of low productivity. Because nesting densities were high and I observed some effects of proximity of nearest neighbor pairs, I suggest these densities (proximate factor) were affecting productivity through reduced food availability (ultimate factor). However, I could not rule out the effects of environmental contaminants, although this seemed unlikely because of the distance of the island from industrial and agricultural areas. I discuss the various potential causes of this low rate of productivity.