This morning, a walk along the High Line Canal Trail in Greenwood Village proved eventful. For most of the walk, a drone — pilot unseen — beat me around every corner. It flew higher than nearly any of the birds, save a large flock of Red-winged Blackbirds.
Wednesday’s snow meant a fairly fresh canvas covered by mammal tracks. Indecipherable ones lined the canal — coyote perhaps, but I’ve also seen a bobcat in the area. Rabbit, raccoon, and rodent tracks crisscrossed the trail.
Down along the Little Dry Creek, signs of beaver activity. Should the beaver have any success at building, their work will certainly be undone. Homes, the trail, and nearby roads all come to close to the creek for Greenwood Village to abide beavers.
A Baffle of Bushtits
During my short walk, I had the good fortune to encounter a flock of 15-20 Bushtits. They were in a productive patch of the canal, along with Chickadees, White-breasted Nuthatches, Juncos, Songs Sparrows, and Spotted Towhees.
Every encounter with Bushtits is magic. They’re incredibly active birds, moving from spot to spot in ways that mean you can never be sure you’ll indeed meet them while birding.
This flock might have been satisfied feeding along the canal, undisturbed by me and my camera. But a Sharp-shinned Hawk had other plans. Entering the scene to briefly perch on a power pole, the hawk inspired the Bushtits to give an emphatic, noisy warning call. They went quite for a time, as the hawk stayed perched. But as soon as the sharpie took off again — flying directly away from the Bushtits — the Bushtits called again.
I’d not heard this vocalization from Bushtit before. Apparently, they reserve it for small avian predators, namely Sharp-shinned and Cooper’s Hawks. Joseph Grinnell documented this in a 1903 essay. Referring to the call as a “confusion chorus,” Grinnell speculates that its radiating intensity causes accipiters to lose individual Bushtits to the din.
A flock of bush-tits will be foraging as usual, with the ordinary uncertain medley of location-notes, when suddenly one or two birds utter several of the sharp alarm notes and then begin a shrill quavering piping. This is taken up by the whole flock, until there is a continuous monotonous chorus. At the same time every member of the scattered company strikes a stationary attitude in just the position it was when the alarm was first sounded, and this attitude is maintained until the danger is past. In nearly every case the
danger is in the shape of a hawk, more especially of the smaller species such as the sharp-shinned or sparrow hawks. No matter how close the hawk approaches, the shrill chorus continues and even intensifies until the enemy has passed. The remarkable thing about this united cry, is that it is absolutely impossible to locate any single one of the birds by it. The chorus forms an indefinably confusing, all pervading sound, which I know from personal experience to be most elusive. This confusion-chorus, as I think it might be appropriately called, is a sure sign of the appearance of a small hawk even a long way off.
It seems reasonable to infer that this monotonous chorus of uncertain direction, at the same time as it sounds a general alarm, serves to conceal the individual birds, all of which at the same time maintain a statuesque, motionless attitude. Their colors also harmonize closely with the shadows of the foliage. The whole evidently forms a composite protective device, which must be, as a rule, effectual.
Beyond the Bushtits, I encountered a female Northern Flicker in a cavity in a cottonwood. She sat or perched deep in it at times, her head barely visible in the cavity.
She stayed in the cavity for some time, perhaps watching me watch her.
What was she doing? We’re months away from when flicker nesting usually begins. I didn’t notice any obvious nest building activities — no excavation of the cavity, no interactions with a mate.
Perhaps the sun, after snow, sparked something — as, for all of us, it tends to.
Fri 17 Feb 2023
High Line Canal Trail–Greenwood Village / Centennial (Arapahoe Co.)
16 species observed
Sharp-shinned Hawk, 1
Northern Flicker, 4
Blue Jay, 2
Black-billed Magpie, 7
American Crow, 2
Black-capped Chickadee, 5
Red-breasted Nuthatch, 1
White-breasted Nuthatch, 2
European Starling, 3
American Robin, 10
House Finch, 9
Dark-eyed Junco, 2
Dark-eyed Junco (Slate-colored), 1
Dark-eyed Junco (Pink-sided), 1
Song Sparrow, 2
Spotted Towhee, 2
Red-winged Blackbird, 35