In 1995, we added a survey of eagles wintering in the interior to our annual swan count. We now have a 25 year history of primarily Bald Eagles using similar open water areas where the swans and other waterfowl congregate, but we do have a much smaller count of Golden Eagles in the general areas as well. While numbers in the interior are expectedly much less than the large aggregations at coastal salmon spawning sites, we have noticed a generally increasing number of eagles in the interior since starting our counts. In some years, numbers appear to correlate with fluctuations in some interior salmon runs, but changes in other food sources such as wintering waterfowl, municipal landfills and agricultural carcasses may be influencing numbers.
Along the South Thompson River this year on Jan. 13, we counted 57 Bald Eagles and no Golden Eagles. This was less than the 96 noted in 2018. Of the total, 12 were sub-adults representing 21% which is considerably less than the 35% noted last year. Bald Eagles do not reach full adult plumage for 5-6 years, resulting in several age classes that can be distinguished reasonably accurately by plumage variation. However, it takes close observations and experience to make reliable distinctions between the various ages, so we simply record 2 age classes. Adults are those with dominantly white heads and tails while sub-adults include all younger birds showing plumages ranging from uniformly dark juveniles through mottled white and brown variations of birds aged from 1- 4 years.
Typical adult Bald Eagle showing clean white head and tail with no black feathering.
This is a juvenile Bald Eagle showing some variation in dark body feathering.
Another variant of a younger Bald Eagle, often mistaken for Golden Eagles.
This bird is about 3 yrs old showing a variation of the Osprey-like dark and light head.
Yet another variation of a sub-adult Bald Eagle.
Golden Eagle on coyote carcass with gold on the head and neck visible.
Golden Eagle with gold hackles clearly visible.
Again, many thanks to the same dedicated group of swan counters who helped spot eagles while we were out.