The Naturalist, By Michael Morris
A pair of Bald Eagles has returned to their nest at the confluence of Tumtum Creek and the Columbia River. This nest of sticks is in a sturdy old tree and has been in use for many years. It can be seen with binoculars from the Greenbelt Trail. Likely, it is the same nesting pair as last year as the more mature eagles are dominant. Without some means of marking them, we can’t be certain of their identity.
Mature Bald Eagles look alike, except that the females are larger than the males, as is normal among all species of eagles, hawks, and owls. Immature eagles look much different than the adults. They’re a mottled dark brown and take about five years to achieve the distinctive white head and tail.
The pair of eagles claiming the Tumtum nest could be the pair that was around here all winter, seen at the landfill site and at the out flow of the Revelstoke Dam where they feed on the stunned fish (usually kokanee) that get sucked through the turbines. Their return to the nest site is their way of claiming their territory. This may have been prompted by the return of eagles that spent the winter on the Pacific coast.
Recently, there have been dozens of eagles, mostly immature birds, appearing at Cartier Bay where they await the thawing of ice to release dead fish they can see frozen in the ice. Eagles eat mostly by scavenging as opposed to actively hunting. They are energy conservers, remaining still through periods of food scarcity. They are more active on windy or sunny days, using the wind or thermals to soar on wings as wide as the outstretched arms of a man. They are searching for something to eat and they won’t hesitate at stealing it from others.
The female usually lays two eggs. The first to hatch dominates, always eating first what is brought to the nest. The second eaglet only survives in years of abundant food. The parents’ territorial behaviour around the nest site isn’t just about claiming the nest but also about ensuring sole access to a prime fishing site.
The sight of so many returning young eagles is heartening as this species was once on the endangered list in the United States. Prior to 1940, eagles in the US could be shot, trapped, or poisoned. The use of DDT, starting after the Second World War, was even more devastating. This chemical concentrated in fish and when ingested by eagles, it prevented the full development of egg shell. The weak egg shells were crushed by the incubating parents. This was discovered by comparing eagle egg shells in museums collected from before the use of DDT. This data made for a compelling argument for the elimination of this chemical in our environment.
Around Revelstoke, eagle numbers are only limited by the amount of food they can find, winter being the most difficult time. So when you observe the white-headed adults, you know that you have seen a proven survivor.