Birds in ‘doughnut’ formations appear on Missouri weather radar. What are they doing?

Birds on their morning commute are popping up on weather radar in “doughnut” formations in Missouri, officials say.

The National Weather Service in Springfield shared radar Monday of “roost rings” in southwest Missouri, which have been frequently visible on clear and calm mornings.

So, what are the birds doing?

The birds, likely purple martins, are flying away from their overnight roosting spots in search of food, officials say.

Though the National Weather Service in Springfield can’t be certain purple martins are behind these roost rings, the species is common to the area and known to gather in flocks large enough to appear on radar.

Purple martins gather in huge flocks in late summer to eat, socialize and rest before embarking on a long migration to South America, according to the Purple Martin Conservation Association.

This practice of “migratory roosting” attracts thousands of the birds to a small area, usually near water or urban areas where they can be found in structures such as bridges or pipes, the conservation group says.

Purple martins are between a sparrow and robin in size with the males displaying dark blue or purple shades and a black tail and wings, while females are gray on the head and chest with a white lower belly, according to The Cornell Lab of Ornithology. They feed on large insects in midair at higher altitudes, which can make them harder to spot.

This story was originally published August 16, 2021 at 3:38 PM with the headline "Birds in ‘doughnut’ formations appear on Missouri weather radar. What are they doing?."