Shirley Jones ("What kind of bird was that?" June 24), you described a unique bird technique called kettling, used by birds getting ready to migrate. They gather in a thermal updraft, circling higher and higher, like a boiling kettle, gaining altitude. Sometimes calling to one another. and appearing to fly quite close together.
I was lucky to witness this activity in snow geese, and they made quite a racket, which attracted us to them. When they got very high, they swung north, moving in a large V flock. Other migrants, especially hawks, do this as well.
You mention the trees being bare at the time, and the birds appearing silver-like, so they might have been snow geese moving north after their winter in the south. Hawks also use this kettling technique, as do vultures and some other migrants.
If you like birds you might enjoy Audubon; check our Facebook page.
Margaret Evans, Decatur
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