Wednesday, May 13, 2009

Swainson's Hawk

High winds today did bring a surprise in the form of this adult intermediate (rufous) morph Swainson's Hawk. Conditions were not exactly favorable for photography, and the bird never got very close, so these two pictures are the best I have. I think you can see that it's a Swainson's Hawk (dark flight feathers, long 'hand'), but as far as age and color morph are concerned, I guess you will have to take my word for it.

Just before the start of the count, I said to my coworker Sarah that today's high winds might bring a surprise. Swainson's Hawk, was her reply. Nah, I said, you need west winds for that. Guess I was wrong!

Yesterday's 'vacuum cleaner' metaphor didn't exactly pan out either. A few new arrivals (Eastern Kingbird, Savannah Sparrow, Bank Swallow) but nothing in any great numbers. The hawk flight too was fairly modest today, with really only good migration of Peregrine Falcon (5), and Sharp-shinned Hawk (97). In the case of the latter, I have to wonder just how many of those birds actually went through, and how many were flying in circles. Other raptor sightings today include 6 Turkey Vultures, 1 Bald Eagle, 4 Northern Harriers, 3 Broad-winged Hawks, 3 Red-tailed Hawks, 4 Rough-legged Hawks, 1 American Kestrel, and 1 Merlin.

The Whitefish Point hawk count usually gets one or two Swainson's Hawks each spring. I thought the window of opportunity on that species had closed last weekend, but evidently I was wrong, and indeed recent records show sightings even later than May 13. In 2006, for example, a Swainson's Hawk was sighted on May 20, and again the very next day. Last year also had two birds, one on April 22 (also the date one was seen in 2007!) and another one on May 8.

Yesterday we looked at some redshoulder and redtail pictures. I have a few more pictures of redtails from yesterday to further illustrate the age / molt story.

This is of course an adult redtail. The wings have an obvious dark trailing edge, and there is no primary panel visible in the hand. The tail is a little shorter than on immature redtails, while the wing is broader, with more of a bulge on the secondaries.

Compare that adult bird with this juvenile, and note the absence of the dark trailing edge on the wings, the light primary panels, and the subtle differences in tail and wing shape, resulting in a slightly different overall shape.

Here's a juvenile bird molting its first primaries. P1 and P2 on this bird are growing in at the same time. Note the dark tips on the new incoming feathers: once they have all been replaced, the bird will have a dark trailing edge on its wings.

Then finally take a look at this bird. As far as I can tell, it's not missing any flight feathers in the wing (maybe a secondary in the right wing, although that could just be some feathers that need reshuffling). Most flight feathers are adult-type, but there are a few retained juvenal feathers here and there. Note that one of the 'fingers' is darker (adult) than the others (juvenal), and that some of the secondaries do not have a dark tip. The bird appears to be missing (i.e. molting) its central tail feather, resulting in a w-shaped tail end.

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