WASHINGTON – The United States is losing 4% of its bald eagle population annually due to consumption of lead from bullets used by hunters to kill wildlife on which eagles feed, according to an elaborate eight-year study. The study also found that the golden eagle population declining 1% a year. The study was published in the journal Science. The study evaluated eagles in 38 states – 1,210 bald and golden eagles including 620 live eagles. In dead birds the toxicity was measured in bones
Verbatim
Todd Katzner, a wildlife biologist at U.S. Geological Survey in Boise, Idaho, a co-author of the study: “This the first time for any wildlife species that we’ve been able to evaluate lead exposure and population-level consequences at a continental scale, It’s sort of stunning that nearly 50% of them are getting repeatedly exposed to lead.”
Bald eagle. Lead poisoning a miserable death. Also a risk to the species.
Eagle population
Bald eagles: Wisconsin has 1,700 nesting pairs of bald eagles. Minnesota has 1,500. These probably are the largest numbers of any state except Alaska with 15,000.
Golden eagles: The golden eagle population in Minnesota, all in the southeast counties, and in adjoining western Wisconsin counties is about 120.
Lead toxicity
Eagles are scavengers that ingest gut piles or unrecovered deer carcasses with spent ammunition inside. In the upper Midwest, a half a million deer a year are killed, mostly with lead based ammunition. The lead enters an eagle’s bloodstream, filters through the liver, and builds up in the bones. As a result, even at low levels, eagles and other raptors suffer gastrointestinal dysfunction, neurological impairment, depression, seizures, weakness and death.
Survival’s Round 2
Bald eagles, the U.S. national bird since 1782, were close to extinction in the 1960s because of the insecticide DDT. The insecticide was used widely in farming. It washed into waterways, contaminated the fish that eagles ate, and poisoned the birds, weakening their eggshells and killing hatchlings. DDT was banned in 1972, and eagle populations began recovering. Today the United States 300,000 bald eagles.
California’s solution
Conservation groups have pushed for bans on lead ammunition. California banned lead bullets in 2019 to protect imperiled condors. An alternative ammunition is copper, albeit more expensive but not prohibitively so. Most hunters, even in California, are unaware whether their bullets are lead or something else.