The issue with "Krider's occurring from California to Arizona" is that there are no substantiated Krider's records west of the Rocky Mountains. All of the reports in that area documented with a photo have turned out to be a light-morph Harlan's (the two subspecies can look very similar to each other). So, the Krider's referenced from CA-AZ is an extraordinary claim. Of course, Krider's could or has already occurred west of the Rockies, and I suspect it will be documented sooner or later for sure. Here are some Krider's and light-morph Harlan's below for future reference (check out the juvenile and its adult plumage a few years later -- follow-up instances like this are invaluable). And a downloadable PDF of a study of Krider's hawks. During this study, we did not see a single calurus from the grasslands of eastern MT to the MN state line south to SD, but did document many Krider's breeding with typical borealis and abieticola: http://www.aba.org/birding/v42n2p38.pdf
Just a side-note, the latin name is spelled "krideri" in Pyle's text, however, "kriderii" is the proper spelling, and describing Krider's as a "morph" is unusual since it has been proposed as a race in the past, may very well be today, and is typically treated as such in literature since it has a distinct breeding range, so defining it as a light-morph variant sounds better. To be fair, I know what it's like to have your ideas questioned. I stated about 7 or 8 years ago that I thought Harlan's Red-tail could be closely related to borealis for several reasons, and was dismissed by some. But recent DNA tests (Hull, et. al. 2010) show that Harlan's and borealis are closely related, and the two are found to freely interbreed. I can't fault anyone who makes mistakes researching the entire list of species and subspecies in North America, my point is to simply help rectify and decipher some issues.
Adult Harlan's
Adult Harlan's
Adult Harlan's
Adult Harlan's
Juvenile Harlan's (left) Adult (right) - Same individual
Juvenile Krider's
Adult Krider's
Adult Krider's
Adult Krider's
Adult Krider's
17 Comments:
Very provocative title, got me quickly reading. I really like finding things out about raptor subspecies. Thanks Jerry! One quick question for you: in the 6th photo down from the top (Jim Lish's photo) it looks like a juvie Harlan's to me with the banded wing tips ... what makes this bird a Krider's?
And, from my reading of the Hull et. al. 2010 article I understood that Harlan's are as closely related to borealis as they are to calurus and that Harlan's is a subspecies of red-tail and not a distinct species on its own. I didn't get the impression of Harlan's being more closely related to borealis at all.
Thank you for those comments Derek!
I read somewhere that the Hull paper said that but I'll check who quoted it. Either way, it confirms through DNA a subspecies. I guess the question is: is DNA enough on its own to merit that? It is a strong point, and I think the combined evidence suggests it anyway, but more study is being done, so we'll see. I'm always open to new stuff.
Krider's often have banded primary tips, a blog post for the near future, I mentioned it in a previous post (link below) but not on its own with photos. They are very similar sometimes, and thereasons for misidentifications in the past. Check out the thin bands on the tail and flight feathers, reddish hue to tail, faint patagials, and limited bellyband. The topside pic is best for ID, but didn't post it. Funny, my next post is on the tail patterns of juv Harlan's I'll post tomorrow.
http://utahbirders.blogspot.com/2012/03/banded-primary-tips-on-red-tails.html
I re-read the paper, and I believe it suggests ithe DNA of Harlan's is more closely related to borealis than calurus? Maybe I am misinterpreting it....that is possible.
I re-read the article too and I see your point now, I agree with you.
I have Pyle's Identification guide but never read this section. I'll admit that after reading this and the previous post I wonder what else in there is wrong. I have a lot to learn about birds, so I don't want to learn poor information.
You gotta admit, though, one of the more difficult things distinguishing between that light morph Harlan's and Krider's. The similarity is tremendous, including the mottling on some of the Krider's primaries, something one tends to associate strictly with Harlan's.
Absolutely Hatem -- and it is the misidentifications that lead to bad data!
I guess there's a reason I go to you with my hawk questions, thank you for sharing your knowledge on this blog it is a fantastic resource.
Thanks for your trust Marc, and thanks for all the great questions you have sent me privately
I am not an expert on hawks but if Krider's is a calurus or both calurus and borealis, I quit!
Hah Seth -- Don't worry, you don't have to quit birding or studying birds (if that's what you meant). Krider's is not a type of calurus.
I live on the west side of Brigham City and saw a white hawk that might be Krider's. Have you seen the white morph this far west? Any other white hawks that size in Utah?
Hi Utahbooklover - There are lots of Harlan's around in winter, so I would think it was a light-morph Harlan's or maybe a leucistic Red-tail, but without a photo I couldn't say with certainty of course.
Utahbooklover, there's a leucistic redtail that migrates every year along that mountain from logan down. that might be the same hawk. I got reports from falconers every year that there's a "white redtailed" along that range.Try to get some photos of it! It seems pretty tame from what I hear.
Matt - I actually have pictures from Bountiful Peak of a leucistic Red-tail, must be the one since it matches the plumage of the other shots I've seen.
How do you tell the difference between a kriders hawk and a Harlan's Hawk? I took some pics of a hawk I've never seen before which was white. Many are saying its a Harlan's Hawk, but others are saying kriders. I'm confused? Wanted to post a couple pics but see now where to share the pics of the bird i captured with my camera.
I'm happy to look at the pics, feel free to send them to jliguori@hawkwatch.org
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