There is a nice place to observe White-throated Swifts where Deer Creek flows through its gap in the Lyons Formation hogback. The area can be viewed from around the junction of West Deer Creek Canyon Road and Buckhorn Road (eBird hotspot "Deer Creek at W Buckhorn Rd"). Park along Buckhorn just over the Deer Creek bridge.
-- The swifts are attracted to an area of the hogback bluff overlooking Deer Creek, shown in the first photo below. There are maybe 20 or so pairs that nest there. Recent visits peaked with 60-80 swifts August 8-11, apparently including local fledglings. Then my visits on Aug 12-18 had only 0-6 swifts, and it seemed the local birds had mostly departed.
I stopped in there tonight, arriving at 6:43 pm (67 min. before sunset) and right off I noted large groups of swifts (80-100 at a time) swarming out in front of the cliff. Once I started paying attention, it was clear that birds were rapidly entering a particular crack -- the roost! -- a zig-zagging crevice with an overhang, maybe 15-20 feet long and 2-3 inches wide (second photo below).
From 6:43 to 7:02 pm it looked as if there was a continual stream of swifts just appearing more or less out of nowhere, swarming, and entering the crack. As they entered, most just flew up swiftly to the crack from slightly below and just shot into the crack, pulling their wings in at the last moment. In some cases they seemed to fly right into the crack. Some birds flew back out of the crack, but the overwhelming flow was of inbound birds. After 7:02 the incoming birds thinned, but there remained a steady but diminishing arrival of birds until I left at 7:15 pm.
I think the number of White-throated Swifts I saw was in the range of 400-500. And it is likely some entered the roost before I arrived. Clearly these were migrants stopping in at this roost. And they are all in that one crack! There was some vocalizing as the flocks flew around, but not very much. As I was leaving the flying birds had ceased calling, but I could hear swifts calling from the roost itself.
There were hardly any birds active other than the swifts, but there was an unexpected evening movement of migrant Northern Harriers. Seven harriers flew over from 7:00 - 7:08 pm, all as singles heading south high over the crest of the Lyons Hogback. It was 4 females and 2 males. An adult Peregrine Falcon also put in appearance, but was likely a local.
The Lyons Formation Hogback overlooking Deer Creek at W Buckhorn Road
Swift roost is the diagonal shadow toward the top of the cliff.
David Suddjian
Ken Caryl Valley
Littleton, CO
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