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Saturday, November 24, 2007

A light Harlan's Hawk

I made a run to the feed store in Hygiene, Colorado yesterday (yeah- that's its real name and yeah, it's a pretty clean place...) I was after corn to keep my Blue Jays happy, but brought along my camera in case I saw anything interesting on the short trip. I'm glad I did.

You see, I'm a bit of a raptor aficionado- I like them all, but one that always interests me in particular is the Red-tailed Hawk. For starters, there are plenty around here, with their numbers growing in the winter as birds arrive from points north to spend the season. Then there's the wide range of individual variation shown within the species, from birds that are extremely pale (actually, if you count albinistic individuals, completely white) to coal-black stunners.

Among the winter Red-tailed Hawks along the Front Range of Colorado, a small percentage are Harlan's Hawks- the harlani subspecies of Red-tailed Hawk. Once considered a separate species, these birds have a fairly restricted breeding range (mostly Alaska and Yukon) and they move into the lower 48 states, primarily in the southern central plains, to winter. Other habitat pockets throughout the western states provide wintering grounds for Harlan's Hawks as well, and once you are east of the Mississippi Valley you would be lucky to find one (for detailed maps on these and other raptor distributions, get Brian Wheeler's comprehensive Raptors of Western North America and Raptors of Eastern North America.)

Harlan's Hawks, like western Red-tails (calurus), are polymorphic, meaning they come in various color morphs (not phases- they are born and live their whole life as one color type- phase implies the color will later change.) Reversing the trend found in their calurus counterparts, dark birds are the most common type found within the harlani subspecies. Light-morph Harlan's Hawks are quite rare, and easy to overlook as just another Red-tail. In the Sibley Guide to Birds, David indicates that light-morph Harlan's Hawks may only comprise 1% of the population. So finding one is cool- a rare form of a rare species.

I saw this bird drop on prey along a road while I was stopped at an intersections and when it didn't immediately fly back up I guessed it had made a catch. When I diverted over to see if I could photograph it on the ground, it flew back up onto a roadside power pole to eat the vole (or whatever it is- anyone venture a guess?) I love that scenario, because raptors with prey are a lot less likely to fly off. The bird let me coast up on it and get a series of pics as it ate lunch- I'll spare you some of the more gory shots (for now, at least.) Once during its meal, it flew to the next pole to finish eating, and then flew off, but I only managed two receding flight shots.

Obviously one striking feature is all of the white on various parts of the head. Its overall color tone was pretty cold- the belly band was fairly heavy, almost black "droplets". With the tail folded it looks nice and red with dark bands, but I think the red is only in the outer two feathers, with the rest of the deck (upper surface of the tail) gray with dark speckling and a dark subterminal band... good for Harlan's. You can see this on the second shot below where the bird is pulling on the rodent, exposing more of the tail. Also, it might just be the light head, but the bird looks a bit big-eyed compared to other Red-tails (like I think Harlan's do.)

And here's the oddest part- the bird called several times, and it didn't sound like a Red-tail. I hear them frequently, and I honestly don't think I would have identified it as anything but some unknown raptor if I had only heard it. The call wasn't as high and shrill as a typical RT- I'm not great at describing sounds but I thought it was more of a croaky sound, lower-pitched and without as much of a whistled quality compared to our "normal" 'tails.

I wasn't sure if I really had a light Harlan's, but after looking at Hawks From Every Angle by Jerry Liguori and Brian Wheeler's books mentioned above I was feeling like it was a real possibility. Now I've heard back from a few experts who have much more experience with these birds who agree with me that the bird is an adult light-morph Harlan's Hawk. Both also commented that they sound a bit different than other Red-tails. Wicked.


Anonymous said...

Great pics Bill,

I wonder if this might be the same individual reported here in winters past by Wheeler/Johnston etc? Maybe likes this area to overwinter?

Scott S.

Anonymous said...

November 25 2007

Great Photos

I'm a middle school teacher from New Canaan CT. I recently was visiting Colorado.

I am writing this comment on your blog to see if you might be willing to help me identify a bird I saw at the top of Aspen MT in CO this past August when I was visiting my daughter.

I'm having trouble identifying I am wondering if it might be a light morphed red hawk, Harlan subspecies. The head was 100% white and so were the wing feathers at the tips.

I would appreciate your comments.

I'm trying to post the two photos on this blog comment but I have not been successful. Could you please let me know your email (it wouldn't open on my MAC when I visited your website) so I would send you the photos.

Thank you very much!!

Sue Leighton Smith

Jeff Bouton said...

Cool bird Willy, I hope the bird stays on so we can look forward to seeing contuing reports and more images.