The U.S. Fish and Wildlife Service (Service) recently announced (pdf) its decision that the Sonoran Desert Area population of bald eagles (Haliaeetus leucocephalus) does not warrant protection under the Endangered Species Act (ESA).  The Service’s conclusion is the result of a revised 12-month finding on a petition to list the population as threatened or endangered under the ESA.  The Service concluded that the Sonoran Desert Area population of bald eagle does not qualify as a distinct population segment (DPS), and that listing the population is not warranted at this time.

The Service originally found that the Sonoran Desert Area population of bald eagles was not a listable entity under the ESA on February 25, 2010.  The Center for Biological Diversity and Maricopa Audubon Society challenged that decision in October 2010.  On November 30, 2011, the U.S. District Court for the District of Arizona ordered the Service to draft a new 12-month finding.

The Service employs a three-step process to determine if designation as a DPS is appropriate.  First, the Service determines whether the population is discrete.  Second, if the population is found to be discrete, the Service determines whether it is significant.  Third, if the population is both discrete and significant, then the Service determines if the species would meet the requirements for listing as endangered or threatened under the ESA.

The Service found that the Sonoran Desert Area population of bald eagles was discrete under the DPS policy, but that it did not meet the significance requirement.  The Service found no evidence indicating that the population is biologically or ecologically important to the species as a whole.  Specifically, the Service found that (1) the loss of the population would not result in a significant gap in the range; (2) the population does not represent the only surviving natural occurrence of the bald eagle; and (3) the population’s genetic makeup does not differ markedly from those of other bald eagle populations.

Despite this finding, the Service took the additional step of determining that, if the Sonoran Desert Area population of bald eagles was a listable entity, listing would not be warranted under the ESA.  The population continues to be protected under the Bald and Golden Eagle Protection Act and Migratory Bird Treaty Act.

The Sonoran Desert Area population of bald eagles includes all territories within Arizona, the Copper Basin breeding area in California, and the territories of interior Sonora, Mexico, that occur within the Sonoran Desert and adjacent transitional communities.