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Eastern dark-morphs?

posted by Jerry Liguori at
on Friday, February 25, 2011 



Are there dark morph Red-tailed Hawks of the Eastern race? A few people have asked me this question in the last several years. First off, the term borealis is synonymous with “Eastern subspecies”, and I use the term borealis more often these days because “Eastern” implies birds in the East only. The true range of borealis is misunderstood (and other races for that matter). Borealis (or at least birds that look identical to borealis) occurs from the East Coast, to central Texas, to the east side of the Rocky Mountains, into southeast Alaska, and across southern and central Canada….that is a fairly accurate “imaginary line” for the most part. There are variations of borealis as it stands today, as some areas of southern Canada are populated with heavily marked Western-looking birds called abieticola, I refer to as “Canadian borealis”, while a pale form called “Krider’s” (named after John Krider) inhabits the northern Great Plains.

To answer the original question…no, dark-morph borealis do not occur. I say this (1) because there is no breeding records anywhere significantly “East”. A dark-morph Red-tail was spotted in upstate NY in or near summer once but was never confirmed breeding or seen throughout the summer. Many dark Western (and Harlan’s) are seen in “eastern” states in winter or on migration, but birds do wander out of their expected range quite frequently. (2) How would one know if a dark Red-tail was a Western or borealis, what traits would be definitive? Having or lacking multiple tail bands on adults is inconsequential; both tail types are seen throughout the entire range of calurus (and much of borealis) and each is more common in certain areas. Same for being completely dark on the underbody as opposed to rufous-breasted. Borealis does interbreed with other Red-tail races where their ranges overlap, so “intergrades” can be terribly confusing to identify to race based on plumage.

Another question asked recently was: Do only Red-tails wearing their first adult plumage show multiple tail bands? An interesting question…Red-tails (referring mostly to the Western race) can have multiple tail bands at any age of adulthood. And, birds in their first adult plumage can lack multiple tail bands.

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4 Comments:
Blogger Tim Avery said...

I would imagine integrades throughout the Rocky Mountain Region north into Canada would be confusing, but I guess the presumption would be that they are integrades due to the plumage, as opposed to being a dark eastern bird.

I know you mention that dark eastern report form New York, it's the one in a million bird I guess... Remember that Harrier you photo'd out at Farmington Bay a couple years ago that was all dark?

Interesting stuff.

February 25, 2011 at 4:48 PM  
Anonymous Jerry Liguori said...

Yes, there seems to be a mix of races and intergrades from Alberta to southern Alaska, Brian Sullivan and I just published a short article that hits on some of this in the latest N.A. birds issue. Much is unknown regarding breeding birds in many northern areas and in much of Canada.

The dark RT from New York is hearsay because there is no documentation (I believe the sighting though), but regardless, it did not breed and could have easily been a younger adult that just lingered along the lakeshores until early summer. That is the only known record at all.

February 25, 2011 at 5:10 PM  
Blogger Seth Cutright said...

Could we not just take the words East and West out of the names? Call them Dark Morph, Light Morph, Rufous Morph, Krider’s, and anything else? Just leave the title East and West off since, as it is pointed out, they don't stay in one location and range is not understood well.

Also since it seems like there cane be lighter western ones and darker, heavier marked eastern ones.

March 5, 2011 at 10:02 PM  
Anonymous Jerry Liguori said...

That is exactly the direction I would love the thinking to move in....but I doubt it ever will with the advancement of digital photography where more detail is being seen nowadays by many more eyes. in "Hawks at a Distance" I don't distinguish some of the Red-tails to race and agree that subspecies stuff is sometimes irrelevant and silly.

March 7, 2011 at 1:12 PM  

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