Eagle Madness

Steve BrennerBanding, ScienceLeave a Comment

When it comes to raptors, eagles often come out on top in every category. And why not? They are massive, long-lived, fierce, majestic, and did I mention that they are very large? Whether it’s soaring past a hawkwatch or giving Gandalf a ride to freedom, eagles are worth looking at every time.

Golden Eagle over observation in the Manzanos (photo by Steve Brenner)

Golden Eagle over observation in the Manzanos (photo by Steve Brenner)

Easily one of the most rewarding experiences of my field work this fall has been getting to know these birds from a distance I never thought possible. In one week our excellent crew in the Manzanos managed to trap and band both regularly occurring North American eagles. Apart from the staggeringly huge measurements, I’ve been surprised by a few aspects of eagle morphology while handling these birds. Both eagles we have caught have been immature birds, and each has provided excellent examples of easily overlooked traits. However, all interesting insights into eagle ID aside, the true wonder of the experience has been witnessing the power and beauty of such an incredible animal up-close.

Spread wing, the amount of white in the axillaries of juvenile bald eagles is staggering. There is also a fair amount of white in the tail of young balds, but as the feathers wear (and even as some get replaced, as in this bird) the white becomes more faded and less bold than in the young golden eagle. Also note the contrast on upper wing coverts on the juvenile bald. Overall, from the topside, it is a much browner, paler bird whereas the young golden is dark. However, beware of the variable size of white patches on the underside and upperside of young goldens. As you can see in this bird, the underwing patches are not obvious, and the white on the upperside is nearly nonexistent. However, the bright white patch in the tail (and lack of molt) put this golden solidly into the first year category.

Another look at the Bald Eagle (photo by Steve Brenner)

Another look at the Bald Eagle (photo by Steve Brenner)

 

Good as gold (photo by Ben Dudek)

Good as gold (photo by Ben Dudek)

The brilliant gold on the head of golden eagles really stands out up close, as does the proportionate size of their bill. In the bald, check out the mammoth bill size compared to his golden cousin. Young eagles can cause ID confusion, so best to look at the head size and underwings if you can. And if nothing else, enjoy the birds. Eagles can’t have all the fun, however. To finish, here is a close up of a merlin and a second-year goshawk. Because raptors are awesome.

Second year Northern Goshawk (photo by Steve Brenner)

Second year Northern Goshawk (photo by Steve Brenner)

Hatch year female Merlin (photo by Steve Brenner)

Hatch year female Merlin (photo by Steve Brenner)