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June 2021 Natural Mystery Answered

posted Jul 12, 2021, 10:51 AM by Jonathan Poppele   [ updated Jul 12, 2021, 3:29 PM ]
Last month’s Natural Mystery turned out to be a little trickier than intended as the feather is a close match for two different species found in the area. Congratulations to Mike Holtz who correctly identified the species. And an honorable mention to Alan Holzer who offered an excellent analysis and pointed out that the best way to distinguish this feather from its closest look alike is by looking at the back.

This is a turkey vulture feather. Specifically, it is a secondary feather from the left wing.

I’ll let Mike get us started with our analysis:

“This is from a pretty good sized bird. Either Barred or Great Horned Owl feathers would have barring on the feather. A mature Bald Eagle feather would be a similar size, but I would expect more consistent dark coloring, or more mottled coloring if not a mature bird. Crow feathers would be darker. Turkey Vultures are definitely in the area, and the size and coloring look good for a secondary feather.”

Alan offers these additional details for how he narrowed down the possibilities:

"In this area, there are only a few birds that have plain wing feathers of this size:  eagles, geese, vultures, herons.  Heron feathers are more of a powdery blue gray.  A goose feather would show a shiny area on either side of the shaft called a tegmen, which provides extra strength for the feather."

That leaves bald eagle and turkey vulture. Now it turns out there is an easy way to distinguish them. As Alan explains:

“With the feather in hand, the difference between bald eagle and turkey vulture is easy to see on the back: the feather shaft on a vulture feather is bright white all the way up on the back, and the underside of the feather is silvery. For bald eagles, the backs and the fronts are similar.”

Unfortunately, I didn’t know that. So it didn’t occur to me to include a photo of the back of the feather. From the front, differences between turkey vulture and bald eagle secondary feathers are more subtle. But there are still some differences. The middle secondaries on turkey vultures show a pale trailing edge and a pale, slightly fringed trailing tip. Bald eagle secondaries have a more uniform color (as Mike noted) and smoothly rounded tips. Have a look at the USFWS Feather Atlas scans for bald eagle secondaries and turkey vulture secondaries. To my eye, the closest match for our feather looks like the fifth secondary on the turkey vulture.

By the way, the second day of our upcoming Track & Sign Evaluation with Marcus Reynerson is International Vulture Awareness Day. No kidding. I'll be celebrating by taking a tracking eval. I hope you can join me.

Congratulations again Mike for sending in a correct answer. And thanks again to Alan for pointing out a key feature for ID when you have a feather in hand.

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