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| A male violet-green swallow lists to the side in the hot sun. July 4, 2014 |
Swallows appear in large numbers at the Dipper Ranch from July through September. They have finished nesting and gather the tribe before they head south for their winter grounds.
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Male panting on the left, female landing on the right
violet-green swallows, July 17, 2010 |
They come in pulses with the numbers I see on the overhead utility wires growing from day to day, then disappearing, then collecting again. Perhaps each pulse is a different group gathering for gregarious migration.
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The one-winged version of listing. A bird would maintain a tilted position for a few minutes.
Male violet-green swallow, July 5, 2014 |
On hot days in the summer, I've seen them list to the side on the wires overhead with their wings spread wide or folded back and throat and breast feathers puffed up.
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| Panting male violet-green swallow. July 17, 2010 |
Maybe the listing is a way to dissipate heat in addition to their open beak panting.
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There's shade nearby yet the swallows choose to land and list on wires in the sun.
July 5, 2014 |
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| This male violet-green swallow tried listing in both directions on the wire as if to treat separate sides. July 5, 2014 |
It could also be a way to heat up body parasites which then crawl to the outside of their feathers where the bird can more easily pick them off while grooming. Why carry an extra load all the way to Central America for the winter?
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| The swallow tribe gathers on the wires above the Dipper Ranch gate September 13, 2011. Yesterday (September 19, 2015) I saw another large group of swallows on a set of nearby wires as I have seen on and off for weeks. |
How many swallows do you think are on the wires above? I've got my own guess.
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Violet-green swallow,
Tachycineta thalassina
Interesting! I've not seen this behaviour in Swallows (we have Barn Swallow, Hirundo rustica, over here) but have certainly seen it in Blackbirds (Turdus merula). My assumption was that it was to remove parasites, though I wasn't aware of the mechanism so thanks for the tip.
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