The population of the bald eagle, the US national bird that is also much revered by Native Americans, reflects political trends in the US.

In the latter parts of the 1900s, the bald eagle faced extinction, or at least extirpation in the Lower 48, from low reproduction. This was caused by their uptake of DDT from the fish they ate. The DDT caused their egg shells to be so thin they broke when they sat on them. For anyone with chickens, you know how variable eggshell thickness is, how much they vary depending on the birds’ diet and if they are getting enough calcium. Too thin and the eggs break; too thick and the chicks can’t break out.

Bald Eagle population in the Lower 48 as measured by annual Christmas Bird Counts nationwide.

Thanks to the Endangered Species Act, signed into law by Richard Nixon in 1973 back when the Republican Party considered conservation a conservative idea, the eagles are returning. They now nest in lakes even around downtown Los Angeles. In some highly polluted areas, such as the waters between Los Angeles and the islands off southern California, eggshells are only just now returning to normal. Everywhere, across the Lower 48, the eagles are coming back. The battle is not over. The Republicans today are trying to overhaul the Endangered Species Act, which could again put this great bird at risk.