Bald Eagle

On the wild side—January, 2012

by Tina Mitchell

Looking in flight like a railroad tie with a white head and white tail, the majestic Bald Eagle is the second largest bird of prey in North America, bested only by the California Condor.  Males and females wear the same plumage although males are considerably smaller.  This distinctive plumage only appears in birds 4 – 5 years old, though.  Prior to that age,  the plumage varies widely, with varying mixes of brown and white.  The scientific name—Haliaeetus leucocephalus—derives from  Latin and Greek (“haliaetus”) for a sea eagle.  (Those reading closely may have wondered about the “ee” in the scientific name—an error made by the person who originally names the species.  The wacky rules of taxonomists require that the original misspelling persist.  Go figure.)  The species name means “white-headed,” (“leukos” = white; “kephale” = head).  The common name denotes that its head appears to be bald when contrasted to its dark body.  Finally, the English word “eagle” traces from Latin (“aquila”), meaning an eagle.

Primarily fish eaters, Balds typically hang out close to water.  The Breeding Bird Atlas workers confirmed 33 breeding pairs in Colorado from 1985 – 1995, mainly on the Western Slope.  In the current Breeding Bird Atlas work, 40 breeding pairs have been confirmed, with another 50 pairs listed as “possible” or “probable” breeders.  In the winter, the state’s Bald Eagle numbers soar as birds from far northern interior areas find their way south.  The timing of this explosion varies, since the primary motivation for the movement arises as open water further north freezes.  In our area, we generally start to see an early Bald Eagle or two in the large cottonwoods and ponderosa pines along the river beginning in mid-November.  After Thanksgiving, the numbers stabilize until mid-February, when the Balds begin to head back north to their breeding grounds.

Scavenging along reservoir shores and rivers, Bald Eagles watch from high perches for dead or stranded fish or crippled waterfowl.  They won’t hesitate to steal food from smaller fish-eating birds such as Osprey too.  When fish are abundant, such as at spawning runs in Alaska, the bird may simply wade into shallow water to grab a meal.

Bald Eagles typically don’t breed until they’ve attained the classic adult plumage at age 4 – 5 years and they may mate for life.  Often returning year after year to the same site, BAEAs build or add on to a massive stick nest, called an “aerie” (good crossword puzzle word!) near the crown of a large tree.  The female lays 1 – 3 eggs at 3 – 4 day intervals.  Both the male and the female develop a brood patch (a highly vascularized area of bare skin on the belly), so both parents share the Incubation duties lasting 34 – 36 days.  Initially both parents feed the nestlings directly with small pieces of food ripped off a carcass.  Around 3 – 6 weeks of age, the nestlings begin pecking at carcasses that the adults have left intact in the nest.  For several weeks prior to their first attempts at flight, nestlings lumber around the huge nest flapping their wings and sometimes hopping to adjacent limbs.  Nest departure occurs from 8 – 14 weeks after hatching.  Fledglings may continue to use the nest as a home base for food for several weeks as they perfect their foraging and flight skills.  Once they leave the nest area for good, they continue to associate with other young and the parents for another month or two.

Starting in the 19^th century, hunting, the loss of nesting habitat, and, later, contamination of their food by pesticides (primarily DDT) decimated the population.  Populations have increased dramatically since 1980 as DDT levels dropped and  environmental awareness increased.  By the late 1990s, Bald Eagles had breeding populations in every Canadian province and in every state in the U.S. except for Hawaii, Rhode Island, and Vermont.

in 1782, Congress selected the Bald Eagle as the national emblem—much to the dismay of Benjamin Franklin.  Perhaps more than a bit tongue-in-cheek, Franklin wrote to his daughter of his objections in 1784.

…the bald eagle … is a bird of bad moral character.  He does not get his living honestly … Too lazy to fish for himself, he watches the labor of the fishing hawk, takes [his catch] from him… For a truth, the turkey is in comparison a much more respectable bird, and withal a true original native of America… He is, besides a little vain and silly, a bird of courage, and would not hesitate to attack a Grenadier of the British Guards, who should presume to invade his farmyard with a red coat on.

As much as I admire and appreciate Wild Turkeys, I have to admit I’m glad that Franklin didn’t win the day.   Somehow, Thanksgiving dinner would have a very different feel if we all pulled up a chair to a delectable meal of the symbol of the nation.  Bald Eagle, it is!

You can read more about this species, find links to photos, and hear a clip of the incongruous voices of this massive bird here.

Photos thanks to Wikimedia Common (photographers, NASA/Gary Rothstein and Mary Lynn Stephenson, respectively).