December Winter Raptor Survey of Rocky Mountain Arsenal NWR and DIA Raptor Alley, with sighting of a mystery buteo
This is our 2nd season doing volunteer Winter Raptor Surveys (WRS) for the Hawk Migration Association of North America (HMANA) since moving to Denver in July 2022. Prior to moving we did 4 WRS in New York State in the Hudson Valley area since 2016.
Last winter season we did 3 surveys here – 1 in Denver and 2 in Boulder in December 2022, and January and February 2023 for each route, following it exactly, and roughly in the same week each month.
This year we added another WRS in the area between Bennett and Jackson Lake SP. We did that route a week ago with nothing special to report. It may improve as winter progresses.
Yesterday we completed the Rocky Mountain Arsenal to Barr Lake, and west of Denver International Airport route for December 2023.
We saw and identified 78 Raptors, including
Ferruginous Hawk 5, all adult
Prairie Falcon 1, which attacked a Red-tailed Hawk as well as a Northern Harrier
Bald Eagle 25
Northern Harrier 10
American Kestrel 5
Red-tailed Hawk 25, including 2 dark morph RT on Piccadilly Road at Barr Lake, one perched and both in flight together. Spectacular.
In addition we had a mystery buteo at 1st Creek at DEN Open Space perched in a tree next to Peña Boulevard at 10:15 AM. When we finished our survey and on the way back we could still see it (presumably the same buteo) at the same location at 4:30 PM while driving south on Peña Boulevard.
Our eBird checklist for that location with images is:
https://ebird.org/checklist/S156663182
My notes written during the observation were: The tail was reddish with multiple equal width bands, no sub-terminal band, with more reddish distally than proximally, as well the left side of the tail was slightly more red than the right side of the tail which was less red. There was a thin eyeline on an otherwise white head with a black blob in the malar area, no belly band but a few speckles in the flank area, white scapulars and coverts.
Liza fancied a Krider's Hawk looking at the Raptor ID app. Looking at Brian Wheeler's Raptors of Western North America at the time, I felt it could be a juvenile light morph Harlan's Hawk, except today reading more about it in his Birds of Prey of the East and looking at the pictures, the back is not stark black and white as his images show.
I sent the images to the WRS coordinator for expert opinions. So far one opinion is that it could be a Krider's Hawk or an intergrade between Krider's and an Eastern borealis Red-tailed Hawk.
Any learned expert opinions with detailed reasons for your ID would be most welcome.
I have to admit that neither of us have ever seen any of these possible species! Our ID speculations are book/image-based only.
You can see what we found on our previous WRSs along the same and other routes at
https://wrs.hmana.org/public_html/index.php as well as the 1 other route developed in the past winter season in Colorado – the Nunn Raptor Alley route conducted by Robert Beauchamp. Go to the website to the left sidebar and click on Survey Map and enlarge it to Colorado, you can click on individual surveys and using the drop-down menu, find previous survey results.
Anyone can develop their own survey route. It is open to all. You can get more information at:
https://www.hmana.org/winter-raptor-survey/
If you like raptors and know of an area with raptors you can develop your own route, as long as it doesn't overlap an established one. Just follow the guidelines on the website. If you want any questions answered you can email the WRS coordinator Janice Sweet. I can also be of help if you want someone local.
Ajit & Liza Antony
Central Park, CO (which used to be called Stapleton)
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