Our story thus far in 2015: The female Bald Eagle has laid two eggs this season, on 2/16-17 and 2/20. You can view the nest on streaming video here. For much of the 20th Century, Bald Eagle eggs were under a huge threat in New Jersey and elsewhere -- first because of egg collectors and later because of DDT. The great naturalist and author John Burroughs wrote in his 1904 book Far and Near that "I once heard a collector get up in a scientific body and tell how many eggs of the Bald Eagle he had clutched that season, how many from this nest, how many from that ... I felt ashamed for him. He had only proved to be a superior human weasel."
According to a 1936 report commissioned by the National Audubon Society, oologists (egg collectors) had robbed three of the five nests in Cape May County the year before, and a Salem County nest had failed to produce young over a 15-year period because of egg collectors. As Bruce E. Beans wrote in his 1996 book The Eagles Plume, A bird such as the Bald Eagle, with a relatively long sexual maturation period and relatively low reproductive rate -- and average of two a year, with often the first hatched the only survivor -- could not long endure such thievery. The next threat to Bald Eagles and their eggs was the overuse of the insecticide DDT, beginning after Word War II. Some of the toxic chemicals in the pesticide got into the food chain and were absorbed into the body fat of Bald Eagles and other animals. Because Bald Eagles have fairly long life spans (up 40 years in the wild) the DDT accumulated in the body fat and affected the Bald Eagles reproduction.
The label on the DDT can boasts of a "long lasting killing effect" -- they weren't kidding. The DDT caused the female eagles to produce thin, fragile egg shells that cracked when the adults incubated them. The United States banned DDT in 1972, and Bald Eagle populations have gradually rebounded since then. In a later post, I'll write about the most amazing N.J. Bald Eagle egg story of all time.
Next week: All about Bald Eagle nests. Yesterday: All About Bald Eagle eggs.
Last week: Bald Eagle basics.
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Jim Wright writes The Bird Watcher columnist for The Record and the Herald-News. He is the author of four coffee-table books about wild places, and the deputy marsh warden of the Celery Farm Natural Area in Allendale, N.J.