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!