Friday, May 8, 2009

Strange buteos

This top bird is not a strange buteo, but - on the basis of just this side view - it's probably not an easy ID for most birders. If you don't know what this is, then let's review what is visible on this bird and see where that gets us.

It's a hawk with rounded wings and a medium-short tail - in other words: a buteo. We see some kind of light panel in the primaries, a light buffy bar across the upperwing coverts, and - for a hawk at least - a small bill. Let's take a look at another photo of the same bird, with more field marks visible.

Here we have a clear view of the bird's upperside. It would probably be easier if we had a view of its underside, because that's just how we see buteos most often. But we can work it out with this upperside view just fine. What else is visible that wasn't earlier? Exactly, the tail. Brown tail with wide dark terminal band and smaller bands on the rest of the tail. That wide dark terminal tail band should suggest Rough-legged Hawk to us, and the earlier noted small bill would confirm that ID. Those light panels in the upperwings are quite characteristic of juvenile Rough-legged Hawk. Juvenile Red-tailed Hawks have primary panels too, but usually not this exaggerated.

Here then finally a photo of the underside of the same bird, and it should be quite clear now that this is a juvenile dark morph Rough-legged Hawk. Those big dark carpal patches are what most birders think of when they think of Rough-legged Hawks, and most of them indeed show that field mark.

I'll admit, this is a rather contrived and elaborate - OK, far-fetched - way to get to my real topic, i.e. 'strange buteos'. What I really mean is strange redtails. Two days ago there was that "Krider's-type" bird, which hasn't been seen since. For those of you who have back issues of Birding on their shelves: that bird was a spitting image of the bird illustrated in the October 2001 issue of that publication, in figure 20, showing a bird captured at a raptor banding station in Braddock Bay, NY. Jerry Liguori, author of that article, suggests that the bird in that photo is an adult Eastern Red-tailed Hawk, probably a Krider's intergrade but not a true Krider's. The head on that bird, like on our bird of two days ago, is pale, but not whitish. I think Wednesday's bird was most likely also an intergrade, not a true Krider's. There are still things to be learned about sub-specific variation in the Red-tailed Hawk; the more you look into it, the more variation you will find.

Today, another pale redtail showed up, but this was a different individual from two days ago. It had a little more spotting on the sides of the belly (still unspotted mid-belly), the head was a fraction darker (but still quite blonde), and the tail was all-red, with a narrow black subterminal band. (The tail on the earlier bird was half-white.) The back on today's bird was extensively speckled with light markings.

Then also today there was an adult 'rufous' intermediate morph redtail, and a juvenile 'rufous' intermediate morph redtail, possibly the same bird that was seen yesterday and the day before of a similar description.

But the real mystery bird was seen in the first hour of the count only. I don't have photos but I followed the bird for a while in the scope, and made extensive field notes:
  • all-dark buteo, shape like redtail
  • slightly smaller and shorter-winged than roughleg, with which it soared for a few moments
  • dark tail with wide dark terminal band, smaller bands on rest of tail (not unlike bird pictured above!)
  • remiges (flight feathers) quite dark! almost as dark as on Swainson's Hawk
  • dark trailing edge on wings (i.e. adult)
  • jizz not like Swainson's, also undertail coverts dark (not light, as in Swainson's)
  • jizz not like Short-tailed, also wingtips not upturned when soaring
  • structure essentially like redtail
So what's an adult dark redtail whose tail is not red? Is that a Harlan's, or is it yet another dark redtail variation?

Good. So much for that 'familiar' buteo, the Red-tailed Hawk, which shows so much variation. Other raptors added to the count today were 7 Turkey Vultures, 3 Bald Eagles, 6 Northern Harriers, 11 Sharp-shinned Hawks, 2 Cooper's Hawks, 3 Northern Goshawks, 196 Broad-winged Hawks, 14 Red-tailed Hawks, 7 Rough-legged Hawks, 1 Golden Eagle, 4 American Kestrels, 2 Merlins, 3 Peregrine Falcons, and one unidentified buteo. Also seen from the platform today an adult female Rusty Blackbird, sadly a bird rapidly plummeting toward extinction. Good sparrow variety at the feeders, with American Tree, Chipping, Song, Lincoln's, White-throated, White-crowned, Vesper and Clay-colored Sparrows present today.

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