Date: 1/9/21 3:53 am
From: <phawk254...>
Subject: [MASSBIRD] Unusual Rough-legged Hawk at Plum Island Continued (long)
On Dec 31 I posted that Julie and I had seen a possible intermediate dark morph Rough-legged Hawk at Plum Island on the 30th. Perched, it looked to be a typical juvenile dark morph, overall a uniform brown, excepting what appeared to be a large white face patch on the forehead. When the bird roused, it briefly revealed what looked more like the underwing of a light morph bird, with paler wing linings accentuated by a black carpal patch, rather than the relatively uniform dark wing linings without a distinctive carpal patch that I usually see on dark morphs in Massachusetts.
I want to thank everyone who sent me photos of what might have been the bird I saw. Two, Susan Moses and Mark Timmerman were able to photograph at some distance the bird I am confident is the one I had seen, showing what I had observed as well as pale primary panels typical of juveniles. The photos were taken at considerable distance but enhanceable to prove helpful.
My interpretation is that this bird is juvenile dark morph best described by Brian Wheeler in his Raptors of Eastern North America (2003). which he notes is a "common plumage type in the East." He writes "Varies from very pale and nearly rivaling those of light morphs to moderately dark with...a fairly defined white mask." On the underwings "Dark brown axillaries, rufous coverts, and a sharply defined large black carpal patch."
Perched at a distance the bird looks like a typical dark morph juvenile or female, saving for a larger, brighter white face patch than I have ever seen before on a dark morph bird. (I'll note that my observations were made roughly 2000-3000 ft from the bird.) The photos suggest the patch is not dramatically larger than usual, but the white clearly "blew out" its periphery when I saw the bird perched. The wing linings are more heavily marked than on a light morph, but not nearly as uniformly dark as what is seen on the typical dark morph bird. I have seen at most two dark morph birds with somewhat similar wing linings in 45 years, and none with as bright a face patch (forehead).
Roughleg plumages are incredibly varied and complex, and are still be described and defined. Recent radiotracking of several migrating Roughlegs by Hawk Watch International reveals that we also have a lot to learn about their wide-ranging movements.
If anyone obtains good photos of this bird in flight, I would be grateful if you would contact me. Thank you to Susan and Mark for their sharing.

Best,
Paul

Paul M. Roberts
Medford, MA
<phawk254...>
 
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