Wednesday, February 11, 2009

All About Eagles

Bald Eagle photograph by Doug Brown

A dedicated raptorphile, I once said that if I could see a wild Harpy Eagle in the South American jungle, I would die a happy woman. Harpia harpyja is the only member of the genus Harpia. It is the largest and most powerful raptor found in the Americas, inhabiting tropical lowland rainforest in the upper canopy layer, where it preys on sloths, monkeys, and other tree-top dwelling animals.

Throughout the world, there are 46 species of eagles, including fish eagles, to which our national bird, the Bald Eagle, belongs, and booted eagles of the family Aquila which includes the other well-known North American eagle, the Golden Eagle. There also is a large group of hawk eagles, none of which might be found in the United States. While many birding afficionados consider only the bald and golden native to our land, another eagle, even larger than the bald occasionally graces Alaska and the northern seacoast with its presence, the Stellar’s Sea-eagle. This species which can weigh up to 20 pounds dwarfs our eagles which rarely weigh more than 10 pounds. It normally nests on the east coast of Russia, but often takes to open water during the non-nesting season, sometimes straying as far as North America.

Our beloved national symbol, the Bald Eagle is probably the most instantly recognizable raptor in the world. However, despite its symbolism, the species has suffered from persecution, and until recently was a federally listed species. At one time Bald Eagles occupied almost all of North America and estimates placed the population prior to 1800 at more than 250,000 individuals. However, as humans began to expand our range on this continent, eagle populations began to decline. In the American West, Bald and Golden Eagles were considered vermin and were shot in the mistaken belief that they were a threat to livestock.

In 1940, the Bald Eagle Protection Act made it a federal offense to kill Bald Eagles everywhere except Alaska. In America’s frontier state, however, they still offered a bounty for eagle carcasses as late at 1953. Then, in 1967, they were listed as endangered under the original version of the Endangered Species Act.

Although direct persecution diminished, the species still suffered from low reproductive success. As a top predator, they were a victim of bioaccumulation. Because most of the bald’s prey is aquatic, either fish or waterfowl, toxins from pesticide residues built up in their systems, causing thinning eggshells and reproductive failure. Populations of Bald Eagle, along with Osprey and Peregrine Falcon crashed as a result of DDT and related toxins. Essentially, these large predators were the ‘canary in the coal mine’ that warned us of these pesticide hazards.

Bald Eagle numbers have rebounded thanks to a more enlightened citizenry, the banning of DDT, and laws that protect not only the birds, but also their nests. Now, in many areas, an active Bald Eagle nest is cause for celebration, and eagle watches and eagle cams are the rage. When it comes to nesting, Bald Eagles may just be downright hospitable. Other smaller species sometimes build their nests in the massive structure that the eagles improve upon each year. These smaller birds receive protection from the presence of the larger predator, and the eagle doesn’t necessarily view a small-medium sized songbird as a food item. At one eagle’s nest along Puget Sound, three live nestling red-tails were found. Because the hawks were younger than the eaglets they could not have hatched from eggs laid before the adult eagles arrived. It is likely that the adults brought the chicks to nest to feed their young. But, they were not killed. Under the right conditions, if a nestling makes a food begging call, the parents treat it as just another mouth to feed. Two of the three red-tail chicks fledged from their surrogate eagle’s nest.

Although Bald Eagles have rebounded, much concern remains about the Golden Eagle population in North America. Some biologists believe that golden numbers are as low or lower now than the Bald Eagle was when it was listed. Goldens face some of the same threats to survival, persecution from shooting and also electrocution on power lines. With their large wingspan of 6-1/2 feet, they can easily span the distance between energized components on utility structures.

There is a thriving black market for raptor feathers in North America, especially eagle feathers. While Native Americans can legally possess feathers under permits issued by the U.S. Fish and Wildlife Service for use in religious ceremonies, collectors often pay exorbitant prices for feathers, feet, and skulls. Ironically, some of the largest documented eagle-poaching rings have involved Native Americans.

International trade in raptors is a continuing threat worldwide, and more than 120 countries have signed the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES), the most comprehensive wildlife conservation agreement ever created. Appendix I includes some 700 species of plants and animals that are critically endangered, including the Bald Eagle, and no legal trade is permitted in these species. Appendix II includes 3,000 animals, including the Golden Eagle, and 21,000 plants that would be threatened by uncontrolled trade, and only limited trade is allowed under certain circumstances. Appendix III includes species already protected by existing laws of signatory countries, but not included in the other two appendices. I

Which brings us back to the Harpy Eagle which was listed on Appendix I in 1975. For me, this species epitomizes the ultimate birding challenge: rugged conditions, bugs and snakes, potentially unstable politics, and the other hazards of travel in a country with only my marginal grasp of the language. I never for a moment thought that one day I might actually have an opportunity to see one of these magnificent creatures. That is, until the day my friend, Sam, called and said, “Jim Black is leading a tour to Venezuela to look for Harpy Eagles! Wanna go?” So, what could I say, except, “You betcha!” Sam and I are off later this week, along with 6 other birders, on a special quest to see our dream bird. Oh, and the several hundred other species that reside there! So, there won’t be a bird article in the March 1 issue of the Thunder. Hopefully, I’ll have the rest of the story for you in mid-March! Bien Venidos.

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