Bald Eagle Timeline: A Halted Recovery

The eagles' recovery was short-lived. About a decade after the Bald Eagle Act gave them protection, a new problem arose with their eggs.

In the late 1940s, bird watchers started to observe that many eagle eggs were not hatching. Investigations found that the shells of the eggs that many raptors, including bald eagles, laid, were too thin for the chicks to survive. Over the next decade, the situation became dire.

1958: “A Very Sick Bird”

"I am firmly convinced that about 80 percent of the Florida bald eagles are sterile . . . . This is the only conclusion I can reach after watching nests in which the eggs have failed to hatch in seven consecutive years . . . . Our American bald eagle—national emblem of this country—is a very sick bird.”

Charles L. Broley, “A Very Sick Bird,” Audubon Magazine, July-August, 1958.

Around this time, researchers counted the number of male and female eagle pairs in nests and found fewer than 417 across the entire lower 48 states. Because shooting the birds and disturbing their nests had been outlawed for over two decades, people struggled to explain what was happening. Scientists reasoned there must be some other cause, but figuring it out would be a team effort, needing input from chemists, biologists, and bird watchers to help solve the mystery.

What was happening with the eagles that made scientists think that something was wrong? Why did they need to investigate?

Timeline Tip: Using Images

When choosing images for your biodiversity timeline, make sure to get permission or use images that are in the Public Domain or that can be shared through a “Creative Commons” license. Be sure to include proper crediting information for the image.