The effects of low levels of pollutants on the reproduction of golden eagles in western Norway.

The reproductive success of golden eagles was studied in an area in western Norway between 62 degrees and 63 degrees N between 1973 and 1999. Addled eggs were collected for analysis of chemical pollutants from nine territories; five from coastal areas and four from inland. The coastal sites had lower annual reproductive output than inland sites, and the eggs had a higher content of organochlorine compounds. There were relatively strong negative correlations between reproductive output and (1) shell thickness and (2) DDE concentration in eggs. The data indicate that the golden eagle may be a particularly sensitive species to DDE. It is proposed that the higher organochlorine content found in the eggs of coastal birds was caused by a contribution of marine birds to the diet, as opposed to inland eagles which have a prey basis consisting almost entirely of terrestrial herbivores such as grouse, mountain hare and cervids. Our data-set on reproductive output is, however, too small to establish a general relationship between DDE contamination and reproductive output in golden eagles.