On the Fly – Higher-Flying Birds

                      "It is good for man
To try all changes, progress and corruption, powers, peace and
anguish, not to go down the dinosaur's way
Until all his capacities have been explored: and it is good for him
To know that his needs and nature are no more changed in fact
     in ten thousand years than the beaks of eagles."

     —from “The Beaks of Eagles,” by Robinson Jeffers

Surely the beaks of eagles, and every other thing about them, loom large in our sense of what constitutes power. Flying thousands of feet high on strong, powerful wingbeats at up to eighty miles per hour, golden eagles (Aquila chrysaetos) can spot their prey a mile away and dive after it at speeds up to two hundred mph!

They’re found on much of the planet—Europe, Asia, parts of Africa, and in North America. They’re featured on the national coats of arms of Germany, Albania, Austria, Egypt, Mexico, and Romania, and they were the basis of the “aquila” standard of the Roman legions.* In Kazakhstan they have been used for centuries to hunt wolves. In Europe only emperors could use them for hunting. In the American Southwest, they may have been the original Thunderbirds.

And the highest density of golden eagles anywhere in the world is in the Diablo Range, of which Mount Diablo marks the northern end. So it’s no surprise that local stories of the world’s creation, very likely including those of the Karkin Ohlones, for whom the Carquinez Strait is named, feature a mythic Eagle and Mount Diablo (and Coyote and Hummingbird as well).

Golden eagles need about sixty square miles to range in, so we don't see them in large numbers, but they do live year-round in the Berkeley Hills and the Alhambra and Reliez valleys, including Briones Regional Park. The other day my friend Judy showed me a family of four that can be seen most days in the area near the “T” of Alhambra Valley Road and Reliez Valley Road. It was awesome! And I mean that in the old sense of inspiring great admiration, apprehension, or fear. Imagine how the rabbits and ground squirrels feel. Golden eagles prefer those small mammals but they also hunt foxes, cats, mountain goats, even young deer, and they will eat birds. If food is scarce, they’ll eat carrion, shooing away the vultures and, in the absence of condors, taking their place at the top of the scavenger guild.

Aside from their magnificence, there’s another reason why our local family of four is special. Eagles usually hatch two eggs, one before the other. The second is apparently for backup: the first eaglet is bigger and stronger than the second, and somewhere between 50 and 80 percent of the time, that first sibling kills the younger one. Maybe the survival of the second bird means our local eagles have plenty of food. Or it might be that the sex of the second sibling matters, but the jury is still out on that theory.

Generally, golden eagles are prospering in this post-DDT era and with the help of the Bald and Golden Eagle Protection Act. Still, large portions of their former habitat are covered by cities and suburbs, and the law doesn’t protect them from being electrocuted by power lines or, more recently, slaughtered by giant wind turbines. Will the exquisitely designed beaks of eagles survive our “changes, progress and corruption, powers, peace and anguish”?

How do you know that the large bird you’re looking at is an eagle and not a vulture or a hawk? Size, color, and flight will tell you what you need to know. Golden eagles' bodies are about two and a half feet long and their wingspan is six to seven feet. They only weigh from seven to thirteen pounds, which, when you take the large wingspan into account and the broad shape of the wings, explains why they can soar so high.

The only other birds this big that would ever appear around here are the California condor and the bald eagle. Unfortunately, you’re not likely to see a condor. The bald eagle, as we all know, has a dark body and a bright white head. The golden eagle, in contrast, is dark brown all over with golden-brown feathers on its head and neck. It might look a little dull until you see the sun shining on it, and then the reason for the “golden” in its common name and “chrysaetos” in its scientific name becomes obvious. Males and females have the same coloring but the females are much larger. Some adult golden eagles have white epaulettes where their wings join their bodies, and the young ones have bright white patches in the centers of their wings and large white areas on their tails. These features darken as the birds mature.

A vulture can look very grand soaring on the thermals, but in the right light you will see the distinctive dark T shape formed by the top of its wings and its body, not to mention its bright red head. And unlike the eagle, the vulture holds its wings in a V shape and tips back and forth when it flies.

The hawk you are most likely to see in the Martinez area is the red-tailed hawk, and it is much lighter underneath than an eagle. Check out the “Compare-2-Raptors” feature at virtualbirder.com (in the "Gallery" photos by Brian K. Wheeler) to see how other local hawks, e.g., red-shouldered, Cooper’s, sharp-shinned, and Swainson’s, compare in color. 

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Note: I can’t resist including another link to Birds of the World on Postage Stamps here. A quick look instantly reveals the prominence of these birds in human consciousness worldwide (golden eagles appear on more postage stamps than any other bird).