A friend sent me some pretty terrific bald eagle pictures taken in Canada, which got me to thinking about these magnificent birds. When I was kid, there were very few bald eagles left on the East Coast. Today, I only have to drive to Wilson Bridge, about 10 minutes away, to see seven or eight of them (or more) in all their glory.
The return of the Bald Eagle is generally credited to a ban on DDT, but that's a lie. DDT did not kill off the Bald Eagle -- lead poisoning did, in the form of bullets shot from rifles.
The short story here is a common one in American wildlife: as guns became more accurate, cheaper and more powerful between 1850 and 1900, game laws did not keep up. The result was a true wildlife massacre. We not only shot out all of the buffalo that once grazed on the East Coast, we also shot out all the passenger pigeons, Canada geese, beaver, elk, wolves, deer, mountain lions and yes, eagles, osprey and no small number of hawks.
Eagles, osprey and hawks were also decimated by the use of pole traps -- leghold traps set on the top of poles placed around fishing nets and barn yards. Nothing kills hawks and eagles faster or more efficiently than a pole trap.
Native Americans did their fair share of shooting eagles too; it takes a lot of feathers to make a bonnet for the tourist trade, and there was no shortage of bonnets being made and shipped east to museums, collectors, and other wealthy patrons.
The graph above (click here to see full-sized graph) shows Bald Eagle populations as tracked by the National Audubon Society's Christmas Bird Count, which has tracked bird populations in the U.S. since 1900.
As you can see, by 1900 -- more than 40 years before DDT was invented -- Bald Eagle populations were vanishingly low. The same is true for Osprey -- another bird unlikely to be misidentified by a dedicated bird watcher. You can pick any non-migrating bird you want and track the data by going here >> http://audubon2.org/birds/cbc/hr/table.html (note Osprey migrate in the North but tend to reside year-round in the South).
Ironically, Bald Eagle populations climbed between 1940 and 1970, when DDT was in full use in the U.S. The reason for this is fairly simple: the Bald Eagle Protection Act of 1940 made it illegal to shoot Bald Eagles. This protection was further expanded when the Endangered Species Act was passed in 1973.
Left to their own devices, and protected from unregulated shooting and trapping, Bald Eagle populations took flight and have now soared. Today, there are about about 8,00 nesting pairs of Bald Eagles in the Lower Forty-Eight, and the Bald Eagle is now a candidate for de-listing from the Endangered Species Act.
Another American success story. Add that to the rostrum of success we have achieved through a marriage between hunters and conservationists: the return of the white tail deer, moose, elk, cougar, beaver, Canadian geese, wood ducks, and wolves.
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2 comments:
Is your source for the table the raw counts from the Audubon bird count?
That count fluctuates mostly with the number of people counting. To assess population strength, and numbers, one needs to do year-over-year comparisons, as the Audubon Society does.
Audubon never claimed a massive spike in eagle populations in the 1950s.
I think the chart misinterprets the data.
DDT absolutely was a barrier to recovery of the bald eagle, and several other predators. You could check Audubon Magazine's back issues, or the historians at Hawk Mountain.
Ed, I used to run the Population and Habitat program for the National Audubon Society so I know the data sets here pretty well. The data is adjusted for obervation per hour per observor. You can run the data yourself at the link supplied.
The observed population climb for Bald Eagles is very rapid (and sustained) with the start of the Bald Eagle Protection Act, and was not slowed down by the introduction of DDT (or sped up by its ban from what I can tell).
I am not FOR DDT -- quite the opposite. That said, the research on DDT and egg shells is not quite as clear as some would have the world believe. For example, egg shells were getting thinner for 50 years before DDT was invented. See >> http://www.sciencenews.org/sn_arc98/4_25_98/fob2.htm So was DDT (or DDE) the main drive or a side car? Either way, I am glad it's gone, but it did not cause Bald Eagles to dissapper or prevent them from coming back.
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