Estimated count trends varied by region. In the Northeast, eagle numbers increased 6.1 percent each year from 1986-2000, whereas counts in the Southwest, Northwest and Southeast were relatively stable. The proportion of survey routes with increasing counts was higher in the North and in the East.
The new USGS analysis confirms other findings that bald eagle populations in the United States are increasing. Still, the increase in winter counts has not been as dramatic as the increase observed in nesting populations throughout the lower 48 states, which increased at a rate of about 8 percent per year over the same period, said Karen Steenhof, coordinator of the annual Midwinter Bald Eagle Surveys and a research scientist at the USGS Forest and Rangeland Ecosystem Science Center. Most likely, this difference is because winter counts include bald eagles that nest in Canada and Alaska, where populations may not be increasing at the same rate as populations in the conterminous U.S., said Steenhof.
The bald eagle, unique to North America, has been the national symbol of the United States for 201 years, ever since Congress chose the bird as a fitting symbol of the new country in 1782. The decline of the bald eagle throughout its range was largely the result of DDT residue accumulation in fish, which the eagles ate. Pesticide contamination caused thinning of eggshells, resulting in premature egg breakage and death of the embryo, as well as in the poisoning of adults.