Anatomy: Patagium, Patagial

Patagial mark on Red-tailed hawk (phto by Chuck Tague)I came across the term “patagial mark” at the Allegheny Front Hawk Watch in November when I was having trouble identifying a passing red-tailed hawk.

Usually red-tails are easy for me to pick out by their size, shape and belly bands but the bird in question had a pale belly like the one pictured here, was far away and was fighting the wind.  A fellow birder pointed out that I could always identify a red-tailed hawk if I looked for the “dark patagial marks.”


The patagium is the stretch of skin on the leading edge of the bird’s wing extending from the head to the wrist.  The noun patagium is rarely used but its adjective form, patagial, is fairly common.

For instance, red-tailed hawks have light-colored underwings and a dark patagial mark, shown here circled in pink.  It’s a good field mark because no other hawks in eastern North American have this combination.  Try comparing the underwings of red-tailed hawks to red-shouldered, broad-winged or (western) ferruginous hawks for a bit of fun.

Another use of the word is in “patagial tags” which are bird bands applied to the wing on large soaring birds so that researchers can read the tag while the bird is in flight.  The tag hangs below the wing so it doesn’t interfere with the bird’s ability to fly.  California condors, our biggest bird, have the biggest patagial tags.  Click here to see a patagial-tagged ring-billed gull Chuck Tague saw in Florida last winter.

So, yes, I knew about those dark spots on the red-tail’s wings.  I just didn’t know they were so unique.

(photo by Chuck Tague, altered to highlight the bird’s patagial mark)

10 thoughts on “Anatomy: Patagium, Patagial

    1. Nancy, where have you found this hawk? (the city/state location of the hawk helps identify it) Also is the stripe in the patagial area or somewhere else? Is the tail red on the top? underside?

    1. Hmmm. Might be a tag, especially if the whole tail isn’t red. Otherwise, if it’s a small raptor it might be an American kestrel. Their undertail is rusty red.

  1. Thank you!!!!!!!!!!!!!! A visual is so helpful. I was trying to figure out what part of the hawk was actually the patagial and your picture really helped! Now I have to check out your blog!

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