By the mid-20th century, bald eagle populations across the United States were nearing extinction. Decades of habitat destruction, direct shooting, and widespread agricultural pesticide use had devastated bald eagle populations. The most severe threat came from DDT, a long-lasting chemical pesticide that accumulated in aquatic food chains. When adult eagles consumed contaminated fish, the chemical disrupted calcium processing, causing females to lay eggs with paper-thin shells that broke under their own weight during incubation. By 1976, New York had only one remaining breeding pair of bald eagles, near Rushford Lake in Allegany County. Even this lone pair repeatedly failed to produce young because DDT had thinned their eggshells so severely that the eggs collapsed during incubation.
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