Monday, April 04, 2005

Return of the Bald Eagle


Bald Eagles near Wilson Bridge, Washington, D.C.

An article in today's paper notes that Bald Eagles in Homer, Alaska are known to attack white cats and small white dogs, such as Jack Russell's. Apparently, the eagles, which flock in large numbers on the outskirts of the town due to a nearby fish canning operation, think anything small and white and running around must be a rabbit and assume it is fair game.

Closer to home, it turns out that Rosalie Island, a small man-made spit of land at one end of Wilson Bridge outside of Washington, D.C is one of the best places in the lower-48 to spot Bald Eagles.

The reason for this appears to be the profuse amount of fish in the river, drawn to this particular spot by algae blooms and "nutrients" pumped into the river from the nearby Blue Plains Wastewater Treatment Plant. Despite the 200,000 cars that pass by the bridge daily, somewhere between 12 and 20 Bald Eagles call the Maryland side of the bridge home.

Bald Eagles have made a spectacular return in the last 30 years, and there are now more than 7,000 nesting pairs in the lower-48, with an additional 25,000 nesting pairs in Alaska, and even more in Canada.

Though DDT is often blamed as the sole cause of Bald Eagle decline, the truth is that the birds were nearly wiped out by shooting and leghold traps mounted on poles for "chicken hawks".

DDT did not arrive on the scene until after World War II, and was banned by 1972. Yet, a close look at the National Audubon Society's own Christmas Bird Count data shows that Bald Eagles were very rare as far back as 1900, and that their number rose (albeit slowly) during the years DDT was being sprayed in the U.S. The same is true for Osprey -- another bird hard to misidentify, but which was decimated both by shooting and by pole-net fishing weirs. It turns out that the decline of Ospreys had more to do with the large birds breaking their necks stooping on fish caught in pole-mounted weirs than it did with the rise of DDT.

This is not to say the DDT had no effect on bird populations (it most certainly did), simply that it was not the determinant variable in the decline (or rise) in Bald Eagle, Osprey, Peregrine Falcon and Golden Eagle populations, as is commonly believed (and reported by organizations such as Audubon).

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