Saturday 28 June 2014

[cobirds] Possible Krider's Red-tailed Hawk outside Lyons

CoBirders,
I led a Boulder Audubon Society field trip today to under-eBirded hotspots within Boulder County.  One of the stops we made was at the St Vrain River Crossing of 63rd st.  We had probably our best luck of the day at this location.  Eastern Phoebe, unIDed empidonax species (too short a look), great looks at Lesser Goldfinches, and a wondrous exceptionally white Red-tailed Hawk.

We didn't obtain any photos of the bird (too focused on my part on teaching about eBird; sorry) but I can offer a somewhat thorough description herein.  My initial thought was "Wow! That bird is so white that it might be a Ferruginous Hawk which would be weird in its own way."  After getting better looks of it flying over us, it had extremely obvious dark brown patagial bars, darker than I usually see on either Eastern or Western Red-tailed Hawks.  However, the rest of the chest was white and I mean nearly spotless (maybe two or three brown streaks on the entire breast).  The underwings were mostly white with minor gray streaks across the flight feathers.  The tips of the wings had limited black as I recall, maybe 1/2 the length I would expect of a Western Red-tailed Hawk.  The tail was white with a very slight tinge of orange on a few of the outer tail feathers.  There was a subterminal thin stripe of medium brown.  The upperwing seemed darker brown than I would expect of Western Red-tail.  I never got to see the "top" or "sides" of the head to see their color, but from below, the head had a white chin (uninterrupted) and had darkish brown solid sideburns.  In flight, it had a minor dihedral (not as great as I have seen from other Red-tails).  It didn't have the wings pushed forward at the wrist.  

Someone is going to ask me if I aged the bird.  My answer is "It had molted, so it wasn't a juvenile."  It is a stretch to  a assume that it was an adult, but I do know it had lost a tail feather or two and there may have been one or two flight feathers that were molted out already.  The back edge of the wing was consistent like I would expect from a juvenile. 

I have entertained many different options for this bird but with the intention of being open I wanted to see what others thought.  My best representative photo of what I saw is a mixture of these two photos from the net:

Let me know your thoughts and if anyone finds this bird again (we saw it three separate times flying right over us and the bridge) I hope you can get photos of any quality.  This bird was so different from the normal it would stand out to most individuals.  

Thanks for any info.

Bryan Guarente
Instructional Designer/Meteorologist
UCAR/The COMET Program
Boulder, CO

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