Date: 8/27/20 9:18 pm From: Mark Rudolph <woodenappleturner...> Subject: [obol] Swift feeding frenzy
I observed a behavior of VAUX'S SWIFTS today that I had never seen before. At about 6 o'clock this evening over our neighbor's property in the Santa Clara area of Eugene, there was a swarm of swifts totaling at least 30 birds and likely more. They were constantly roiling around and through the tops of two 60' tall cottonwood trees, one of which is mostly dead or moribund.
They were engaging in what I would call "stall-out" gleaning as opposed to the hover gleaning engaged in by other species. With the wind coming out of the north, the birds would fly into the wind from the south and time their momentum and trajectory such that they would briefly stall right at a twig or branch, apparently grab a food item with their bill from the tree and then drop to regain speed and maneuverability for full flight. The swarm did this repeatedly for at least 20 minutes, and then, apparently, the hatch was over as they suddenly left.
I've never observed swifts take a food item from a stationary object. At least I'm assuming they were feeding because I never actually saw any insects, although I was probably over 100' away. There were a few House Finches, Goldfinches and Cedar Waxwings also apparently feeding while perched in the tree. The Waxwings would occasionally sally out to grab something out of the air.
It would be quite the feat to figure out their built-in air traffic control!