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Red-tails of Weld County, CO

posted by Jerry Liguori at
on Friday, August 16, 2013 

I asked Cathy Sheeter to write about the area she lives since it produces many interesting Red-tailed Hawks. Thanks for your time and photos Cathy! And check out her artwork and photography at <www.cathysheeter.com>

About eight months ago I moved from the city to rural Weld County, Colorado. Little did I know that I was moving to a hawk Mecca! While I have enjoyed nature photography for years and could identify hawks, I had little knowledge of subspecies. Then I met Steve Mlodinow, who introduced me to the concept of subspecies in birds, and Red-Tailed Hawks in particular. He then introduced me to Jerry, who also helps me fine-tune my observational skills.
     When I first started looking, really looking at Red-Tailed Hawks around Weld County, I quickly found there were lots of Red-Tailed Hawks that didn’t seem to quite fit the mold for either pure Eastern (B. j. borealis) or pure Western (B. j. calurus). I was told that Easterns were uncommon in this part of Colorado, so I was perplexed to see nearly equal amounts of Eastern-looking (pale-breasted / white-throated) birds, typical Western birds, and in-betweeners. It seems that Weld County may be quite a zone for Eastern x Western intergrades. Of course, with the overlap in traits between the two subspecies it can be impossible to determine the exact parentage of many birds, but some birds seem to show clear traits of both. Undoubtedly, the most interesting birds seem to have some Krider’s traits along with Western traits! It seems that these two subspecies should not overlap in range, but we now know that they do.

     I thank Jerry for his never-ending patience and feedback with the myriad of photos I send him of various odd hawks as I continue to try and document and learn about the Red-Tailed Hawks around me. Without his feedback I might still be in the dark about intergrade looking birds. Below are a few birds photographed in June and July 2013 in Colorado that seem to be intergrades. I hope you find them as interesting and intriguing as I do, and if you ever find yourself around this part of Colorado, take a close look at the Red-tails you might encounter.

Bird 1: At a glance, this adult might appear to be an Eastern with its white throat, faint bellyband, and pale scapulars, primaries, and head. But what of those rufous barred legs? Further support for some Western influence is found in the broad patagials, rufous barring to the underwings, and faint bands on the tail feathers.  Also, the upper tail coverts are a mixture of dark and light.

Bird 2: It’s hard NOT to notice this adult bird’s pale pink tail with thin sub-terminal band! This alone suggests Krider’s influence somewhere in the family tree. Additional support for Krider’s influence are pure white upper tail coverts and (noted by Jerry) rufousy upper wing coverts, hints of rufous in the primaries, and pale upperwings that exaggerate the banding in the primaries. Notice the minimal bellyband, but with Western type barring (and rufous tones). The patagial bars are broad, the head and throat are dark, but it has a pale supercilium.

Bird 3: This adult bird also has a notably pale pinkish tail suggesting some Krider’s influence, and mostly white uppertail coverts. The upperwing is slightly mottled whitish. The patagial bars are broad with rufous tones. While spotted on the belly in an Eastern fashion, there is barring on the underwing linings and suffusion of rufous to the chest. In addition, this bird shows very faint bands on the tail. I was surprised to see the new growth tail feather was bright and normal red. Jerry has photos of similar Krider’s types on the breeding grounds. I have seen this bird in the company of another lightly marked bird (inset). When perched together this bird’s body tone was noticeable paler, and the head was more worn with a pale supercilium and streaked throat. 

Bird 4: This bird falls on the other side of the spectrum from bird 1. At a glance, it appears Western with moderately barred flanks, rufous tones to the chest, and multiple but faint tail bands. However, upon closer exam this bird shows unusually pale scapulars and primaries. The throat is very lightly streaked and the legs are almost pure white. The patagial bars are not particularly broad and the underwings are relatively unmarked. 

Bird 5: If you see the topside of this bird first, you might assume it is a typical Western -- or if the underside is the first glimpse you get, how about a classic Harlan’s? This bird photographed in winter in Weld County appears to be a Harlan’s intergrade (likely with Western due to it being a darker bird). And that’s another neat thing about the location, the wintering hawks!

                                                                                     Cathy Sheeter


 Bird 1
  Bird 2
  Bird 3
  Bird 4
 Bird 5
12 Comments:
Anonymous Anonymous said...

Pretty cool birds, and sounds like a good area to visit any time of year. Keep the posts coming on raptors, my favorite group of birds.

Thank you.

August 16, 2013 at 3:24 PM  
Anonymous Vic Berardi said...

Excellent post Cathy and Jerry! It never ceases to amaze me the degree of variation in Red-tailed Hawks. It is a constant learning experience with evolution in the making. Great photos and always look forward to Jerry's insight on what the heck we're looking at sometimes . . .

August 17, 2013 at 7:06 AM  
Blogger Jerry Liguori said...

Thanks Vic,


It is always nice and helpful when people like you and Cathy share their photos for the rest of us to see!

August 17, 2013 at 7:18 AM  
Anonymous Derek Lyon said...

I was in Weld county recently and didn't see many RTs at all, mainly Swainson's and Ferruginous. I'm from central Canada and seeing a RT that isn't an eastern bird is really rare. I'm amazed and envious, being able to see the various subspecies of RTs, and intergrades too. Thanks Jerry and Cathy, great pics.

August 17, 2013 at 11:47 AM  
Blogger Jerry Liguori said...

Thanks Derek, and thanks Cathy!

August 18, 2013 at 10:16 AM  
Blogger Bryce said...

Aren't Red-tails the best! I love your discussion and break down of each hawk Cathy. And I'm so impressed with the photos.

I'm always excited to look at RT's, because you never know what you might find. So much variation!

Great post. Thanks Jerry, and Cathy.

August 18, 2013 at 3:45 PM  
Blogger Jerry Liguori said...

You are such a Red-tail fan Bryce!

August 18, 2013 at 5:31 PM  
Blogger Cathy Sheeter said...

Glad you guys enjoy seeing my "local" birds! I enjoyed reading the comments. And thanks Jerry for posting this :)

August 18, 2013 at 8:24 PM  
Blogger Jerry Liguori said...

Cathy:

Any time you want to post, just let me know.

August 19, 2013 at 7:09 AM  
Anonymous matt said...

I've noticed that even here in utah, there are no two redtailed hawks that look the same. Kind of like a fingerprint. It's subtle. We rarely get Harlan's, or krider's if any. my recent falconry redtailed had a lot of the typical borealis morph but with a subtle eastern variation. and much richer red hues. I trapped her near vernal in Nov of 2005. So I wonder if she was from colorado now that I read this.
And I can liken this post to the variations of anatum peregrines with their overlapping territories and inter subspecies crosses with peales. Or the three subspecies of Merlin falcons. I've seen columbarius Richardson crosses, sukleyi, columbarius crosses within the same clutch. There's so much overlap and crossbreeding. So it makes for some of my more interesting conversations with other falconers.

August 19, 2013 at 12:13 PM  
Blogger Jerry Liguori said...

Hi Matt

Thanks for the comment.

August 19, 2013 at 3:41 PM  
Anonymous Hatem Gomaa said...

I've heard this place is tremendous. What's the best time to get out there, fall or winter? How about hotels and car rentals? Just kidding about the 2nd Q. :)

December 8, 2013 at 7:25 AM  

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