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.

The Bald Eagle - A Tumultuous Journey

Photograph by David Powell


“For my own part, I wish the Bald Eagle had not been chosen the representative of our Country. He is a bird of bad moral character. He does not get his living honestly. You may have seen him perched on some dead tree near the river, where, too lazy to fish for himself, he watches the labour of the fishing hawk; and when that diligent bird has at length take a fish, and is bearing it to his nest for the support of his mate and young ones, the Bald Eagle pursues him and takes it from him.”

“With all this injustice, he is never in good case but like those among men who live by sharping and robbing he is generally poor and often very lousy. Besides, he is a rank coward: The little King Bird, not bigger than a sparrow, attacks him boldly and drives him out of the district. He is by no means a proper emblem for the brave and honest Cincinnati of America who have driven all the King Birds from our Country . . .”

“I am on this account not displeased that the figure is not known as a Bald Eagle, but looks more like a Turkey. For the truth, the Turkey is in comparison a much more respectable bird, and withal a true original Native of America . . . He is besides, though a little silly and vain, a bird of courage, and would not hesitate to attack a grenadier of the British Guards who should presume to invade his farm yard with a red coat on.”

Benjamin Franklin
January 26, 1784

So began the rocky road of the National Bird of the United States, the majestic Bald Eagle. Unappreciated and feared, all raptors were viewed as varmints by the general populace, even after the Migratory Bird Treaty Act was passed in 1918, and the 1940 passage of the Bald and Golden Eagle Protection Act. Humans have been the most significant cause of mortality for the Bald Eagle and other raptors, and it has only been in the past 35 years that their persecution has declined. Early settlers shot and trapped Bald Eagles because of their perceived threat to livestock, competition for game, or tradition such as the use of feathers by Native Americans. This practice continued; however, even after the above laws were in place. Shooting, trapping, and intentional or accidental poisonings were responsible for 38% of the mortality of Bald Eagles recovered from 1963 to 1984 (Wood et al. 1990). Over 128,000 bounties were paid in Alaska from 1917 to 1952 because Bald Eagles were thought to impact salmon fishing. Significant numbers of Bald, and especially Golden Eagles, were shot by ranchers in western states earlier in the 20th century because of suspected livestock depredations. One such incident, which occurred in Wyoming, involved the shooting of >770 Bald Eagles for which the shooters were paid $25 per dead eagle.

The eagles were further persecuted by those that collected their eggs, a common practice up until 1940. Bald Eagles also suffered from reduced reproductive success due to eggshell thinning related to DDT poisoning. Population declines of eagles, Osprey, and Peregrine Falcons particularly in the eastern US lead to the ban of this pesticide in 1972, but not before the Bald Eagle (1966 and 1978) ) and Peregrine Falcon were listed under the Endangered Species Act of 1973. Since then; however, population trends have increased for the three species most affected by this chemical. In the early 1980s the nationwide population of Bald Eagles was estimated to be 70-80 thousand birds, and that number had grown to 100,000 by 1999.

This recovery represents on of our nation’s most successful conservation stories. By the late 1990s, Bald Eagles were successfully nesting in all but 2 of the contiguous United States. Interestingly, although most citizens now revere our national symbol, today lead poisoning is considered a significant cause of mortality, and has been reported in 34 states. The source of the lead is the pellets and bullets in hunter- shot waterfowl, deer, and other game species. Other factors continue to affect populations such as collisions with vehicle, electrocution on utility structures, and an unknown number that are killed annually for their feathers which are sold on the illegal feather market.

The adults are easily distinguished by the characteristic white heads and tails, and bright yellow bills and feet. The youngsters; which are very similar in appearance to their cousin, the Golden Eagle, often defy identification. Beginning life as a mostly dark brown bird with a black bill, they undergo a variety of plumage changes before they acquire the adult plumage at age 4, when they are sexually mature. The record longevity in the wild is 28 years, with a captive Bald Eagle surviving until age 36. It is likely that, similar to other raptors, mortality is high the first year, with increasing survival to adulthood.

In New Mexico, we generally see the Bald Eagle only during the winter months, where they are primarily feeding on waterfowl, particularly wintering ducks. The numbers of eagles present here during the winter is largely affected by the weather up north. If those lakes are frozen, forcing ducks and other waterfowl further south, likewise the eagles follow their food source. By the time you read this, most of our birds will be heading north for nesting areas located near large bodies of water. Fewer than 8 pairs of Bald Eagles nest in New Mexico, mostly in the northernmost counties, but during the winter months they might be observed just about anywhere, even far from the nearest river or lake. I’ve seen them calmly roosting in canyon country far from any water source, not surprising for a bird that can go 5-7 days between meals.

Speaking of meals, this article would probably have been much different had Benjamin Franklin has his way with our fledgling country. Thanksgiving might have been celebrated in a very different style!