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Back in early October Mrs. burnt out and I took our cameras and went for a drive over to a natural area a few miles from here, planning to take some pictures of the fall foliage that was nearing it's peak. We did go home with some pretty nice pics of the colorful woods that day, but what started me down a long and winding road  that led to this diary wasn't the colors of the leaves but the colors of a beautiful pair of Red tailed Hawks that we saw floating gracefully over a ridge top.

We had been standing just below the ridge, taking pictures of turkey vultures as they spiraled up on rising air thermals over the ridge top when this bird suddenly appeared above us.


We scrambled to focus on it before it too was carried up and out of range on the rising thermals. After watching and trying to keep up with the slower and somewhat more predictable circling vultures the Redtail seemed to be moving at high speed in comparison and I was having a great deal of trouble even finding it in the viewfinder, let alone keeping up with it once I did. Even Mrs. burnt out, who is much better at getting pics of flying birds than I, was having some trouble. But we, (read that mostly  as she), did manage to come up with a few pretty nice pics , before it had drifted out of camera range.

Then as we were trying our best to get and keep the bird in our viewfinders, another one drifted over the ridge top and into view, more or less following the same route as the first one. Though they were both obviously Red tailed Hawks with somewhat similar plumage, there were also differences. I had seen enough Redtails to know they came in various plumages but had never really thought too much about it. These two birds, traveling so close together got me to thinking about the color variations and piqued my curiosity enough to do a little research on it. That curiosity put me on a path that eventually led to this diary.


When I decided to write this I had no idea what I was getting myself into. It's a much  more complicated subject than I had imagined and what I ended up writing  turned out to be quite different than what I had originally planned. And a much longer read that I fear may be too lengthy for some. I've scattered a few pictures of some other Redtails here and there just to break up the monotony of the long read and give your eyes a break. The pics were taken by Mrs.burnt out and myself, (the better ones are hers) and most are typical of the Redtails that we have in this area. All the birds were shot from within a few miles of the house with the exception of the very last one which we saw at the World Bird Center near St. Louis where we had taken an injured Barred Owl a couple weeks ago.

I began with a simple google image search for Red tailed Hawks to look for similarly marked birds. But although I did find pics of similar hawks, lots of them, they told me little. Some were labeled simply as Redtails, some as Easterns, some as Westerns, others as light, intermediate or dark morphs, and some were labeled as Kriders or Harlans. A few were completely mislabeled Coopers or other entirely  different species. Some were practically all white, and others almost black, with many variations in between those two extremes.  All were beautiful but there seemed to be no common denominator as to what factors contributed to whatever name the individual photographer had given to them.


After my initial look at the images failed to be of much help I began looking for detailed written information that dealt specifically with plumage color. This in turn quickly led me to discussions on the various races or subspecies of Redtails.  As it turns out there has been much  written  on this subject, enough to keep you reading for a very long time. But problems soon become apparent once you start trying to sort through it all. The first thing I figured out  is that there is a great deal of disagreement on the subject, even among people that I would consider experts. It is very difficult, no, make that impossible, for an amateur like me to say who is right and who is wrong. The confusion and disagreements are tied to the birds own morphology which is quite complicated and has everything to do with the different colors possible in Redtails.


To begin with there are many subspecies of Redtailed hawks, and even that number isn't totally agreed upon. In north America alone, as near as I can figure out, most ornithologists count five individual subspecies. These include Eastern  (B. j. borealis), Western (B. j. calurus), , Fuertes (B. j. fuertesi), Alaska/Grinnell's (B. j. alascensis) and Florida (B. j. umbrinus). There is a long and ongoing argument that there are two other distinct subspecies , Harlans and Kriders. Both have been listed in various field guides at one time or another as being individual species, subspecies, or as color morphs. Disagreement continues to this day and there are some pretty compelling arguments on both sides.

Subspecies, by definition, are classified as such by having distinct morphological characteristics and defined geographical breeding ranges with very little overlapping from one to another. That sounds simple enough that things could be sorted out pretty quickly but once you start looking into that you'll find that any "facts" you thought you may have found, disappear like a duck in the early morning fog.


 The fog begins with the fact that the individual subspecies each have their own various color forms, or more accurately, color morphs. For instance the Western race has, in addition to the normally colored birds, three additional color morphs, dark, intermediate, and light while the Eastern birds have two color morphs, pale and dark. And these morphs differ from subspecies in that they are not geographically distinct and can even, and often do, occur together in the same nest. So these morphs merge into one another, varying from some birds being very dark to others that are quite white, and everything in between.

And confounding the issue further is that, even though, as I mentioned above,  the different subspecies do have geographical separate breeding ranges, some overlap does occur along the edges. And where that happens, the different subspecies do interbreed and obviously the genetic traits of the two get blended together in the offspring. Those cross bred birds could show the color of either parent, a mix of both, or of neither. And this isn't even considering the fact that a bird you see outside of breeding season may be far out of it's geographical breeding range since many northern birds do migrate and overwinter south of their home territory.


On top of that, in Montana and the Dakotas even lighter colored birds can be found  which are commonly called Kriders.  As I mentioned earlier, at one time Kriders were considered to be a completely separate species, not a Red tailed hawk at all, but most recent discussions I've found on it refute that idea now. Some do still consider it to be a distinct subspecies but if having a defined geographical breeding range is a factor in distinguishing subspecies then they should not be considered as such since their range overlaps widely with both Eastern and Western subspecies.  They are believed by others to be the result of crosses between one color morph or another, of Easterns and Westerns and to me this makes some sense but I'm not going to bet any part of my pension on it.


One final group of Redtails are the Harlans which inhabit central Alaska, eastern
Northwest Territory and northwestern British Columbia but winters in the western United States and in the Great Plains. These are generally darker, some almost black, but they also  produce color morphs of their own that range from very pale to very dark. As I mentioned above, their place in taxonomy is highly disputed, some claiming that they are an individual subspecies of Redtails while others claim they are simply color morphs, and others claiming that the Harlans are in fact not Red tailed hawks at all, but a completely separate species. This argument is decades old and is still going strong today.
 I found this very interesting discussion, where the participants argue over both the species and the age of the bird in question. There are interesting arguments on both sides and if you're still with me it's worth the read.


I found other articles on that same subject and from what I can gather the opinions seem to presently be leaning towards Harlans as being a distinct species, although there is still quite a bit of disagreement over it. Reading these discussions I started wondering if there had been any genetic testing done since that seemed to me to be an obvious way to get to the truth, so I decided to look around to see if I couldn't find any information dealing specifically with that aspect of it and surprisingly I found that there has been quite a bit of research done on that, not only with Redtails but several other species of hawks as well.


As happened often while researching this diary, I was almost convinced by those arguing that the Harlans were a separate species when I found this  article which creates much doubt, in my mind at least, that the argument that Harlans are a distinct species has much merit. Even calling it a subspecies and separate from other races of Redtails is a stretch from what I gather from it. As near as I can tell the data from this study shows that interbreeding does occur between Harlans and other subspecies of Red tailed hawks, particularly with Easterns. If that is true then I don't understand how it can be called a separate species or subspecies. Too me, those results put it squarely in the realm of color morphs. Up until I found this work, everything I had read was for the most part little more than opinions. Opinions often based on a great deal of experience with and observation of the birds themselves, but still just opinions. This article comes out of science and when it comes down to it, I have to go with the science, even when it goes against the views of people whose opinions I would otherwise respect.  Maybe I'm looking at it wrong, it's very possible. Some of you who've spent more time studying this may be able to enlighten me and please don't hesitate to do so. This whole thing began as a quest to educate myself on the subject and any light you can shed on it will be much appreciated. To be honest, that article was, for the most part, several thousand feet over my head. I spent as much time on Wikipedia looking up the meaning of unfamiliar words as I did reading the article. (matching mole, that whole article would be right up your alley I bet. I was sweating blood trying to wade through it but it would probably just be some light reading for you.) But what I took from it is simply that the genetic makeup of Harlans does not show any significant difference from Eastern Red tails that would place it in a class by itself.


 The following can be found under the heading "Evolutionary Interpretation of Data"

The genetic data described here do not support the historical designation of B. j. harlani as a distinct species [18,57]. The lack of significant differentiation between B. j. harlani and B. j. borealis in the microsatellite data suggests that gene exchange between the two subspecies occurs at a relatively high level, and the lack of reciprocal monophyly among haplotypes is inconsistent with differences expected at the species level. Furthermore, the absence of field evidence demonstrating assortative mating among B. j. harlani individuals relative to B. j. calurus or B. j. borealis and the apparent interbreeding with neighboring subspecies [19,58,59] also supports recognition of B. j. harlani as a member of B. jamaicensis, and not a distinct species. In fact, under some criteria, the pattern observed between B. j. borealis and B. j. harlani is inconsistent with differentiation expected among subspecies or "evolutionary significant units"
The gist of that article can be found under the heading of "Conclusions" and it puts it like this.
These data suggest recent interbreeding and gene flow between B. j. harlani and the other B. jamaicensis subspecies examined, providing no support for the historical designation of B. j. harlani as a distinct species.

 So,you can draw your own conclusions as to whether it is possible to identify a subspecies of Redtailed Hawk by it's color. This is my first serious look into the subject and to be honest I'm somewhat confused by all the variables that can and do come into play. So for me personally, I don't believe it's possible to make a positive  ID of subspecies based on the color of the bird in question.  After all my research, that's a very disappointing conclusion, (and a bit humbling to have to admit it)  but that's what I've come up with. So I'm going to have to be content, for now anyway, with just calling our two birds very cool Redtailed Hawks.

This diary barely scratches the surface on the subject of plumage variation and  identification of the different subspecies Red tailed Hawks. As I mentioned, I found a wealth of information about it, far too much to include all of it in any one diary. But it was difficult to decide what to include and what to leave out since practically everything I found on the subject has one or more opposing opinions about it. At times it became very frustrating when I'd find something I felt was useful enough that I'd make a note of it, and add it to my draft, only to later find an opposing point of view. And then the fact that there is a limit to how much I could reasonably expect the readers to wade through before I lost them. As it is, even after attempting to lean it down a bit, it's still a big chunk to swallow.  This being my first venture into this area I'm not really qualified to say that this idea or that idea is the correct one. And I know  that there are others right here on DK who have previously studied this subject and have much more knowledge on this subject than myself. I welcome your input as I'm eager to learn more about it. Anyone else who, like me, is interested but uneducated on this and would like to look into it further can easily find reading material enough to keep you busy through a lot of rainy days. But be forewarned that you may end up more confused than before you began looking for answers.


I'm actually hesitant to even publish this diary since it doesn't even come close to reaching the goal I had in mind when I started doing some research for it. I had hoped to identify exactly what subspecies of Red tailed Hawks we had seen that day and at the same time, gain some knowledge that would help me identify other Red tails that I see in the future, and then to pass that information on to you the readers. Unfortunately I haven't been able to sort out any useful information that would get me there. But having already committed to it, I guess I'll put it out there in spite of all that and maybe some of you with more knowledge can untangle some of it better. But if nothing else, I've given you an idea of how difficult, (if not impossible)  it is to make field IDs concerning subspecies of Redtails. The only consolation I have is that it appears that I'm not the only one who doesn't understand it. And I also take heart in the fact I can enjoy the beauty and majesty of these birds even if I don't know exactly what I'm looking at.


Originally posted to Backyard Science on Sat Nov 10, 2012 at 09:59 AM PST.

Also republished by Birds and Birdwatching and Community Spotlight.

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