Swans are now heading south to escape the ice, but last February they were heading north to breed. Consequently, twice a year they are feeding in our area as they pass through.
Last February, I posted about spread-winged trumpeters: http://blog.kootenay-lake.ca/?p=32321. I had watched the Trumpeter Swans for an hour or so: first feeding, then preening, and finally spreading their wings. There were 18 swans, each of which underwent the same routine. It became clear that the visually appealing spreading and flapping of the wings was just the final stage of the preening.
First, a swan would spend time using its bill to interlock feather barbules that had become separated, and as a final step, it would spread its wings to align wing feathers that pointed askew. At this point, it was ready to fly.
In last February’s posting I mentioned that “[J]uveniles also spread wings”, but I did not show any. During the present southward migration, I watched this year’s juvenile preening by both using its bill to interlock barbules and then spreading its wings to align the feathers. Two pictures follow.
The juvenile is interlocking wing barbules while its parent looks on.
Subsequently, it spread and flapped its wings to align the feathers.
Alistair, your photos and their accompanying text are always fascinating. If you’d begun this when you first went to UBC you might have become an ornithologist rather than a physicist!
Intriguing topic! Imagine adjusting, rearranging tiny barbules with a bill the size of a swan’s. And I’m reminded of how dogs methodically groom and shake their layered coats to regulate warmth.