Nature on Trail: Eagles and Salmon

By Sylvia Feder

As fall fades into winter, many Pacific Northwesterners retreat to their houses where they will wait it out until the rain abates sometime in June. We hikers keep venturing in the great outdoors–and in the damp and dark, we have the privilege of witnessing an ancient natural cycle.

That cycle involves two quintessential northwest icons - eagles and salmon – and no where does this cycle play out more vividly than the Skagit River. This river valley in northwestern Washington supports one of the largest wintering populations of bald eagles in the lower 48, with an estimated 600 to 800 birds flying in from as far away as Montana, Canada, northern California, and even Alaska.

Eagle numbers typically peak in early January, coinciding with the spawning– and dying – of the large chum salmon run. During this time, bird watchers on foot, in vehicles and in boats, gather to take in this spectacle, watching hundreds of eagles scavenging at the river’s edge, perching on cottonwood trees, or soaring overhead. Interestingly, some researchers think that communal feeding grounds such as the Skagit offer significant benefits to young eagles. Not only is food abundant, but when they are surrounded by adults, they may also be learning how scavenge and picking up other survival traits.

Scavenging on dead salmon is typical bald eagle feeding behavior. Contrary to our image of eagles as proud hunters, eagles often feed on dead and dying salmon, steal food from other birds or scavenge carrion. (In small towns in Alaska, some of the best places to see eagles are the town dumps.)

The Skagit River salmon buffet is short-lived and, when the salmon run ends, the eagles make their way up or down the coast to catch other salmon runs. Fewer than 20 nesting pairs reside on the Skagit year round.

Eagles are generally faithful to their nesting sites, as well as their mates; they will return year after year to the same nest, usually in a large dead tree, adding to their home until the nest becomes an enormous structure that can weigh up to one ton. Eagle courtship is an elaborate aerial dance in which the male dive-bombs the female and locks talons with her, free-falling together and swooping up just before they hit the ground.

Female eagles may lay two or more eggs, but typically only one chick will reach fledgling age. A larger chick will often kill a smaller one, or a chick may not make it through her first winter. Relative to other eagles and hawks, bald eagles remain in the nest for a long time. For three months, chicks will be fed by both parents as they grow to nearly their parents’ size. They continue to be fed even after they leave the nest and begin to fly.

Young eagles are harder to spot, as they don’t develop the trademark white head for several years, but seeing young birds perched in the trees around the Skagit River is an indication of how far this species--once on the brink of extinction--has come.

This article was originally published in the November+December 2010 issue of Washington Trails magazine.