Bald Eagles in the Adirondacks
The bald eagle
is not only
our nation's most recognizable natural symbol, and the only eagle found
exclusively in North America, it is also the endangered species act's
prominent success story, and a reminder of how important are the
our wildlife, critical habitat and natural resources generally.
The number one killer of the bald eagle in America today is lead poisoning, which the eagles pick up while scavenging the remains of game, mainly white tailed deer taken by hunters using lead based bullets, which shatter on impact, sending lead shards into flesh, often away from the path of the bullet. This is a problem easily solved by having hunters switch to solid ammunition, such as copper, but the NRA sees this as an attempt to take your weapons.
That’s like saying that when the state mandates seat belt use, that is an attempt to take your car, but such is the ridiculous logic employed in polarized political debate today. No one is saying don’t hunt, just change the type of ammunition you use. States like California have made this argument academic, by banning the use of lead ammunition, just as many states have banned the use of lead sinkers, which can be mistaken for pebbles and swallowed as aids in digestion by loons and other waterfowl.
The bald eagle, a relative of the white tailed eagle found in temperate areas of Europe and Asia, lives only in Canada, the U.S. and Northern Mexico, with eighty percent of bald eagles found in Alaska, and the density of eagles more pronounced along the west coast, particularly from Alaska down through British Columbia. Bald eagles are the largest North American raptor, averaging six and a half to fourteen pounds. and they are rivaled in size only by the golden eagle, which averages about a pound less. One bald eagle, unfortunately shot in New York in the 1890s, weighed in at 18 pounds.
All raptors display sexual dimorphism in size, with females being larger than males, and in the case of bald eagles, females average twenty five percent larger than males. We really don’t understand exactly why females are larger. My guess is the division of labor, with females spending more time on the nest than males, incubating eggs, and larger size is an advantage when defending the nest, while speed and agility are more important in hunting. Without a blood test, male raptors can’t be visually distinguished from females, and gender is usually guessed by size.
A large female measures about 36 inches in length, with a wingspan of 72 to 90 inches, and they can fly between 30 and 35 mph. They soar with a flat wing formation, and the wings are so powerful, they aid in swimming, as when an eagle tries to drag heavier prey through the water, pumping with those wings. As with other birds, eagle bones are hollow, making eagles lighter and better able to fly.
Like your fingernails, their beaks, talons and feathers are composed of keratin. Eagles have about 7,000 feathers which are moulted individually in sequence from head to tail over about six months, which explains the gradual streaky transformation of the head and tail from brown to white. During their first year, immature eagles grow larger feathers than their parents to provide greater lift and compensate the lack of fully developed flight muscles. This is why first year eagles often look larger than their parents. Eagles make discordant, squeaky, gull like screams, which is why Hollywood movies substitute the more pleasing-to-the-ear cry of the red tailed hawk in scenes where eagles are featured.
Eagles also conform to Bergmann’s Rule, which says that average individual size is determined by suitability of habitat, such that larger animals are more likely to retain body heat and survive in colder climate, thereby surviving to pass along genes for larger body size when breeding. Bald eagles in Alaska are considerably larger on average than those in Florida. Bald eagle migration follows similar patterns, with eagles in colder climates moving further south in winter than those in more temperate climates, most of whom remain in their territories.
Bald eagles are usually monogamous, and a mating pair will use the same nest every year, like a home owner, constantly tweaking it and adding to it, with the result that bald eagle nests can measure ten feet wide and ten feet thick, weigh up to a ton and are the largest nests of any bird, aided by the fact that eagles can begin mating by their fourth or fifth year, and can live over thirty years. The record size nest is two and a half tons, but some nests eventually collapse under their own weight, and a new nest has to be constructed. The nest of our oldest bald eagle, Sylvia, was blown down in a Pacific storm while she was still a fledgling, resulting in the permanent disabling which resulted in her living with us. Her two male siblings were successfully rehabbed and released.
Nests are typically located very high in old growth conifer or hardwood trees, ranging from only twenty feet above water when the tree’s trunk is in the water, to 125 feet high when the tree is on land , protruding above smaller trees, and within two miles of large bodies of both salt and fresh water, with most within sight of open water. All else being equal, for example, the potential for scavenging deer and other carrion, and for kleptoparasitism, stealing fish from ospreys or carrion from other scavengers, a nesting pair will generally require a lake of at least four or five square miles in order to make a living.
Eagles cluster where the opportunity for fishing and scavenging is greatest. When on the Kenai Penninsula in Alaska, on the way to Homer, there is an old Russian Village called Ninilchik, where the fishing boats dump unwanted catch in Cook Inlet, and there are always dozens of bald eagle on the beach there in the warmer months. Homer Spit and the Chilkat River north of Haines are other areas of large eagle gatherings.
Immature bald eagles are often confused with golden eagles, as the white head and tail feathers, signs of sexual maturity, don’t finish gradually showing through feather moulting until the fourth or fifth year, as the developing white streaking becomes solid white. Other signs which differentiate bald eagles from golden eagles are the fact that golden eagles have feathers up and down the legs, like trousers, and a lighter brown plumage, as immature bald eagles start out a darker brown before the white feathers begin appearing.
We have a bald eagle at the Refuge who was shot as an immature eagle, but featured leucism, an excess of melanin, which led to lighter feather patterns to such an extent that we thought at first that it might be a young golden, until the head and tail streaking gradually showed it to be a bald eagle. Bald eagles also tend to have larger heads and beaks than goldens, and northern bald eagles have longer beaks than do southerly bald eagles. Immature bald eagles have darker beaks which gradually become solid yellow in maturity.
Eagles are strong fliers with incredibly powerful talons. The general rule seems to be that an eagle can carry and fly with prey up to half its body weight. It’s talons exert a grip of ten times a human’s hand, so somewhere between 500 to 700 pounds per square inch, which is nearly equal to a grey wolf’s bite, and why eagle handlers use those thick padded gloves. The rear talon is often used to puncture and kill prey held immobilized by the three front talons, as the talons on the other foot and the beak are used to tear prey apart.
Bald eagles not only have sharper vision than we have, but a wider field of vision. As with other raptors, eagles have a nictating membrane, an extra transparent eyelid which protects, moistens and cleans the eye. Eagles see in ultraviolet light, enabling them to detect urine trails of potential prey, just as UV enables some winter browsers like reindeer to spot lichen against the snow. Birds puff up their feathers for better insulation and to appear larger to predators.
Courting involves spectacular flight displays, with dives, swoops and aerial acrobatics in which eagles clutch each others talons and tumble through the air.
Eagles nest and breed earlier than other raptors, with the female laying one to four eggs in sequence between mid February and mid March, depending on climate and latitude, with hatching between mid April and early May, and branching and fledging late June to early July. As with some other raptors, older and larger siblings, those which hatch first may monopolize more food from its parents, by pushing younger siblings out of the nest. Eaglets grow quickly, gaining up to six ounces per day, beginning to flap their wings at 8 weeks, fledging between 8 to 14 weeks, and finally leaving the nest area about 8 weeks after fledging.
|The number one killer of Bald Eagles today is the use of lead bullets. Gut piles left behind by hunters contain lead shards, the remains of lead bullets which tend to shatter and scatter upon impact. Bald eagles, along with many other less charismatic scavengers, ingest the lead, which often proves toxic. Please ask your hunter friends to switch to non-toxic copper bullets! Predictably, the NRA is opposed to any restrictions on the use of lead ammunition, our National Symbol be damned. For more information, click on this box.|
Ben Franklin on the Bald Eagle as our National Symbol
Ben Franklin, the statesman, philosopher, naturalist, inventor
and all around Renaissance Man, was not all that thrilled with the
choice of the Bald Eagle as our national symbol, and seemed to prefer
the wild turkey as a utilitarian symbol, which is uniquely American,
and often spelled the difference between our wilderness forefathers
eating or starving. In a letter to his daughter, Franklin said, in
"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 taken 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 & 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 therefore 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 vain
& silly, 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."
Of course, these days we often call politicians "turkeys", but
I believe we have a different meaning in mind.
So....was Ben correct?
Well, yes and no. Bald eagles are opportunistic predators, and we have seen them steal fish from our local ospreys, but that is fairly standard behaviour for predators. Grizzlys will try to steal kills from wolves, but if there are more than two wolves, they will tease and harass the grizzly, until it gives up and leaves. Ravens will lead wolves to a winter killed-moose, but when the wolves are finished gorging, and are just lying around, the ravens will cover the carcass, but instead of eating, will cleverly steal and cache chunks of meat, hiding the cache from the wolves and other ravens, to assure a larger take, than if they simply stayed at the carcass and ate. Lions occasionally lose a kill to hyenas, so the rule seems to be, if you can accomplish it without too much risk, sometimes by sheer force of numbers or overwhelming size or strength disparity, it's often easier to steal someone else's prey than to secure your own, particularly when prey is scarce, and your stomach is complaining.
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Ralph Waldo Emerson
DEDICATED TO MY FELLOW TRAVELLERS IN AUGUST, 1858
Wise and polite,--and if I drew
We crossed Champlain to Keeseville with our friends,
Next morn, we swept with oars the Saranac,
Northward the length of Follansbee we rowed,
The wood was sovran with centennial trees,--
'Welcome!' the wood-god murmured through the leaves,--
Ten scholars, wonted to lie warm and soft
In Adirondac lakes
Look to yourselves, ye polished gentlemen!
Ask you, how went the hours?
Our heroes tried their rifles at a mark,
Two Doctors in the camp
Lords of this realm,
Hard fare, hard bed and comic misery,--
Our foaming ale we drank from hunters' pans,
Nor doubt but visitings of graver thought
And presently the sky is changed; O world!
With a vermilion pencil mark the day
A spasm throbbing through the pedestals
We flee away from cities, but we bring
The holidays were fruitful, but must end;
Adirondack Wildlife Refuge & Rehabilitation Center
Steve & Wendy Hall
PO Box 555, 977 Springfield Road, Wilmington, NY 12997
Toll Free: 855-Wolf-Man (855-965-3626)
Cell Phones: 914-715-7620 or 914-772-5983
Office Phone: 518-946-2428
Email us: info@AdirondackWildlife.org