Ageing Golden Eagles to a specific year can be tricky because the amount of white in the wings varies in extent until adulthood when the white is absent, and wing molt can be difficult to assess without lots of practice. So, the best thing to key in on is the tail pattern and molt. Using the tail to age Golden Eagles is often much easier and more accurate than using overall plumage and wing molt. Of course be careful of birds with adult tails that have one or two secondaries with white at the base. In these instances, the tail has just been fully replaced of the last few sub-adult feathers, but the wings are one or two feathers behind. This occurs typically in birds that still have extensive white in the sub-adult remiges (secondaries and primaries), and take a bit longer to appear all-dark in the wings than some other Golden Eagles.

One more thing -- SY (2nd-year, meaning a year older than juvenile) sometimes only molt one or two tail feathers, a few inner primaries, and minimal body feathers, looking nearly identical to juveniles, so beware of scrutinizing every eagle. Anyway, I just wanted to talk a little about eagles, here are a few tails to check out, the first two birds are 2nd-years (note the several new sub-adult featherson the first bird but the second bird is only molting one tail feather), the 3rd bird has molted 3 times making it a 4th-year, and the last bird is an adult (but don't be fooled by that "slash" of white at the base of one of the tail feathers - adult GE feathers can still have a bit of white near the shaft (as can other species but often only seen in the hand).