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Phalarope713

Red-tailed Hawk subspecies

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Subspecific ID of Red-tailed Hawks (RTHA) is a very thorny issue. Before man's extensive and extreme impact on habitat in North America, subspecies of RTHA probably meant more than they do now. However, with us providing literally millions of acres of new suitable RTHA habitat, those disjunct subspecies have been brought into contact, thus decreasing the differentiation among them.

Colorado has one primary breeding subspecies -- calurus -- Western RTHA. Prior to the coming of white man, Colorado's eastern plains had very few trees, and RTHAs need trees. With the alteration in river flows (due to water management) of Colorado's two main eastern rivers -- the South Platte and the Arkansas, both rivers developed a cottonwood gallery forest, which enabled borealis -- Eastern RTHA -- (and a host of other eastern species and subspecies that were formerly absent from the state) to colonize eastern Colorado. It also enabled Western RTHA to colonize the plains from the foothill edge, thus bringing the formerly disjunct (as far as CO is concerned) subspecies into contact. The resultant gene flow in both directions now means that many, if not most, resident RTHAs in eastern Colorado are mutts. There is still an obvious influx of Eastern-type RTHAs into eastern Colorado in fall/winter, but these birds don't breed there, so winter is the time of year that RTHAs with the appearance of Easterns and seeming to lack Western features are more likely.

In my experience at latitudes similar to those of Colorado from Colorado through Ohio to New Jersey, adult Eastern RTHAs generally sport little in the way of belly bands, while those in areas farther north (my experience is mostly from Michigan) are much more heavily marked. Light-morph Western RTHAs exhibit large and dark belly bands.

While your bird has the pale throat typical of Eastern and "wrong" for Western, your bird is a juvenile (note distinctly yellow eye) and juveniles are a crap shoot, plumage-wise. The throat is more heavily marked than is typical of juvenile Eastern RTHA, as are the upper sides. Whether that's within the range of variation for Eastern RTHA or not, who knows. Personally, I'd call this a RTHA and leave it at that.

Edited by Tony Leukering
fix typos
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Isn't it strange that this juvenile has an unbarred or very faintly barred white tail?

I've read at the Raptor ID group on Facebook that it can be very hard to tell with juveniles, and that's where I'd ask about this one.  But I've been told there that some of my photos (in New Mexico) are in the range of variation of both Eastern and Western, and as Tony Leukering says, they end up as just Red-tailed.

Do you have any shots, even bad ones, of the upperside or the spread wings?

Edited by Jerry Friedman

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On a semantic note, a single individual is not a subspecies... or species. Unless doomed to extinction. At least in birds. in certain whiptails and many, many taxa of the "lower" classes of organisms, a single individual might recover the taxon.

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4 hours ago, Tony Leukering said:

Subspecific ID of Red-tailed Hawks (RTHA) is a very thorny issue. Before man's extensive and extreme impact on habitat in North America, subspecies of RTHA probably meant more than they do now. However, with us providing literally millions of acres of new suitable RTHA habitat, those disjunct subspecies have been brought into contact, thus decreasing the differentiation among them.

Colorado has one primary breeding subspecies -- calurus -- Western RTHA. Prior to the coming of white man, Colorado's eastern plains had very few trees, and RTHAs need trees. With the alteration in river flows (due to water management) of Colorado's two main eastern rivers -- the South Platte and the Arkansas, both rivers developed a cottonwood gallery forest, which enabled borealis -- Eastern RTHA -- (and a host of other eastern species and subspecies that were formerly absent from the state) to colonize eastern Colorado. It also enabled Western RTHA to colonize the plains from the foothill edge, thus bringing the formerly disjunct (as far as CO is concerned) subspecies into contact. The resultant gene flow in both directions now means that many, if not most, resident RTHAs in eastern Colorado are mutts. There is still an obvious influx of Eastern-type RTHAs into eastern Colorado in fall/winter, but these birds don't breed there, so winter is the time of year that RTHAs with the appearance of Easterns and seeming to lack Western features are more likely.

In my experience at latitudes similar to those of Colorado from Colorado through Ohio to New Jersey, adult Eastern RTHAs generally sport little in the way of belly bands, while those in areas farther north (my experience is mostly from Michigan) are much more heavily marked. Light-morph Western RTHAs exhibit large and dark belly bands.

While your bird has the pale throat typical of Eastern and "wrong" for Western, your bird is a juvenile (note distinctly yellow eye) and juveniles are a crap shoot, plumage-wise. The throat is more heavily marked than is typical of juvenile Eastern RTHA, as are the upper sides. Whether that's within the range of variation for Eastern RTHA or not, who knows. Personally, I'd call this a RTHA and leave it at that.

Thanks so much for the information! With what you have said, I agree that it is probably best to leave this bird as "Red-tailed Hawk."

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