A Genetic Analysis of Bald Eagles in the Pacific Northwest: Retained Genetic Diversity Following a Large-Scale Population Bottleneck

Bald eagle (Haliaeetus leucocephalus) populations in the continental United States experienced a dramatic population decline during the twentieth century. Populations across the species’ range have largely recovered, thanks in part to the ban of DDT, rapidly enacted conservation measures, and reintroduction efforts. Using six microsatellite loci, I tested the genetic variation of bald eagles across six states in the Pacific Northwest. Genetic analysis revealed that, despite undergoing a population-wide decline, the bald eagles in the locations sampled outside of Idaho did not exhibit the characteristics typically associated with a genetic bottleneck (i.e., a reduced number of alleles and a heterozygosity excess) and likely persisted through the DDT-era with stable genetic variability. Furthermore, there was no significant genetic structuring in the Pacific Northwest samples outside of Idaho, suggesting a panmictic population across the area. The bald eagle’s long generation time may act as an intrinsic buffer against the loss of genetic diversity and aid in retaining genetic variability across its range. The retention of genetic diversity in these isolated populations likely reduced the effective time of the bottleneck and contributed to the genetic similarity of the populations sampled in this research