The Park

Green Lake’s Eagles

March 2, 2015 7:43am

Face it Greenlakers, living where we do evokes a serious amount of “pinch yourself, I can’t believe we live here” moments. The lake changes so often and even in February we can still see an impressive amount of flora and fauna. I had a moment like this recently when I saw the bald eagles that are often visible on Duck Island or ca-cawing above the lake float effortlessly above the walking path. This made me wonder… how many eagles do we have here in Green Lake? Where do they go in the summer? Why are they here? We asked our go-to nature expert Martin Muller about the eagles.

SG: When are the eagles here in Green Lake? Is it year round?

MM: The eagles usually leave during the summer and nest elsewhere. They return in the fall and usually nest in Woodland Park area.

In our area adult eagles that form a breeding pair will spend most of the year in or near their territory (area defended from other eagles). Outside the breeding season this defense may consist of the adults sitting in high conspicuous perches and calling together as other eagles “trespass.” In spring, males may chase trespassing males, while females will chase trespassing females. Birds of the opposite sex often “flirt.” During winter you will often see immature birds visiting territories. The adult territory owners may escort them away or tolerate them somewhat. Tolerance does not necessarily have to mean this youngster is an offspring of the pair.

Around this time of year the adults get more defensive. Other adults in the area know exactly where every other eagle territory is, and especially after a number of overcast/rainy days, the first sunny afternoon many eagles will ride thermals up to hundreds if not thousands of feet high and check out how everybody else is doing. Trespassers will be chased by territory owners. Sometimes fights will ensue, with adults sometimes locking talons and spiraling to the ground in a “game” of chicken. This is also how immature birds find out where the good territories are. Every time they stray into an adult pair’s air space they will get their “behinds whooped.”

SG: I often see eagles by themselves. Is that normal?

MM: In a healthy population there are numerous non-breeding adults. As soon as a “vacancy” becomes available (a member of a breeding pair disappears/dies) the remaining member of the pair may recruit a new mate. Since adults eagles may spend well over half the year on activities related to raising young (from refurbishing the nest through incubation, rearing of nestlings and fledglings), they can’t afford to go through protracted mourning periods and maybe lose a chance of breeding that year. Back in the early 90s the breeding female in Discovery Park collided with a helicopter over Elliott Bay. The injured bird was fished out of the bay and eventually was used in educational programs, since she had lost the capability to fly (outer third of one wing sheared off). Observers of the Discovery Park eagles (myself included) were concerned that the eagle we saw on the evening news on TV might be the Discovery Park eagle, so we went and checked in the park (in November). We found two adult eagles there (the day after the incident), and assumed it must have been an other adult bird that was injured. Later the next spring when we observed longer and more closely we discovered (by some subtle plumage differences and especially behavior) that there was a new female in Discovery Park after all. Apparently the male had replaced his lost partner within a day.

SG: How can you tell the eagles apart?

MM: Unless the bird has a very distinct feature by which you can identify the individual (and this may be something like a brown spot over one eye on the white head, or a particularly high-pitched voice; or a band or other marker put on the bird by researchers), one should not assume that birds seen in a territory have to be the same birds from one year to another. Or that immatures hanging out with adults have to be their offspring (the exception is when the young raised by a pair leave the nest and stay around for at least a month before striking out on their own in July/August). It takes immature birds between 4 and 6 years to attain adulthood (and the white head and tail and brown body). During those years they can range far and wide but it also is not impossible that they periodically drop in on their parents. But again, if they show up in the spring they will be told to leave in no uncertain terms.

In some areas eagles migrate (because water freezes over and food is less available). That results in congregations of eagles in areas with lots of food during winter. So after early-winter salmon runs along rivers like the Skagit are done, eagles tend to wander down to the river deltas. That’s why you can see several hundred Bald Eagles on the Sagkit and Samish Flats during January-March.