GOLDEN EAGLE NESTS

Last week I found a new eagle eyrie. At least I think I found a new eagle eyrie. It sits toward the top of a low cliff, about 25 feet up. No birds were visible through the binoculars, nor whitewash on the rock face below, but a tell-tale lining of green leafy twigs confirmed that the nest is in use. Brooding Golden Eagles (Aquila chrysaetos) are shy birds, and the adults usually slip off the nest before they can be seen. Their closest relative in these parts, the Ferruginous Hawk (Buteo regalis), is often nearly as bashful, and a nest in this situation could belong to either bird. Once I'm sure the egg(s) have hatched, I'll move in for a closer look.

Five years ago I found a nest in a similar site, that could have belonged as easily to a Ferruginous as a Golden. It was late May, and I hiked up to the cliff to inspect it. I had to climb the cliff several yards to the east of the eyrie site, then traverse across a ledge. As I closed in, I saw a dark body feather stuck to the rock face. I was disappointed; I had hoped for Ferrugies, whose feathers are paler. Once I reached the feather and saw its glossy blackness though, my disillusion became complete. It was a raven feather. They've taken over an old eagle nest, I thought. Creeping across the cliff a bit further, I suddenly found myself face to face with a single fat tiercel Golden Eagle chick. The nest and the rocks below were littered with dozens of raven wings. This eagles' parents had developed an usual specialty.

A Golden Eagle nest usually contains ample evidence of its occupants' diet. The young birds are well provisioned, and it's typical to find a big fresh Jackrabbit (Lepus sp.) in a nest, along with the mummified remains of many previous meals. In fact, this might explain why Goldens are so secretive around the nest. Raptor nests are usually quite easy to find. Red-tailed Hawks (Buteo jamaicensis) will usually start circling 30 feet over your head once you get too close to the nest, giving that beautiful scream, kyee-eer! The intensity of their displeasure is easy to gauge, and they'll lead you straight to the nest in a game of warmer and colder. This is typical of birds of prey, but the Golden Eagle, the one raptor capable of mounting a seriously intimidating threat, invariably sneaks off timidly. As a teenager, I once stole a jackrabbit from an eagle chick and cooked and ate it. Perhaps the Indians of the American West developed similar habits. If humans ever raided eagle nests to the point where they became at all important as competitors with the chicks, the behavior of inadvertently leading humans to their nests would become an adaptive encumbrance and would be dropped. This would also explain why the Golden Eagle is such a highly revered bird in the traditions of practically all the tribes that historically shared its range. I have no evidence to back up this idea, but it's an interesting thought.

Although jackrabbits are the Golden's chief prey, the birds are capable of taking a wide range of creatures. They are the most important predator of Sage Grouse (Centrocercus urophasianus)--morning lekking sessions are invariably broken up by an eagle attack. Anyone who's flown falcons a lot in this area has probably lost at least one bird to eagles. They look slow and sluggish, but much of that is attributable to their size. An eagle moves fewer body lengths per second than a Peregrine, but he can nearly equal that smaller bird in speed. Goldens form close pair bonds, and regularly hunt as a team, and when a pair of them sets their sights on your falcon, there's nothing you can do but stand helplessly and watch.

A Golden Eagle's clutch almost always consists of two eggs, and siblicide appears to be surprisingly common. It seems to me this would tend to decrease the ratio of the smaller, weaker tiercels to hens, but I've seen no evidence of such an effect. Goldens take longer to grow up than any other predatory bird in our region. The incubation period is about 35 days, and the chick's first flight doesn't occur until it is over two months old--more than twice the age of most raptors.

I'm lucky to live in a region that contains fewer humans than any other part of the temperate zone. The Mountain West still enjoys close to a maximum carrying capacity of Golden Eagles, even though I've watched the population of my state more than double in my lifetime. The cliff where I found my first eagle eyrie was recently blasted away in favor of a highway, and each year thousands of acres of eagle habitat are usurped for human pursuits. Ever-expanding McMansion subdivisions and ski resorts bring disturbance ever closer to incubating birds, and the unfortunate new industry of spring helicopter ski trips is destined to become an important eagle threat. For now, though, a 30-minute bicycle ride from my front door can still take me to at least two different eyries, and the sight of those glinting golden hackles is still an unremarkable privelege.
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illustration: THE SUNNING STONE--GOLDEN EAGLES (1988) oil 24" x 18"