Radar in Northwest Indiana detects roost rings from birds that are most likely purple martins

Roost Rings were detected Saturday morning on radar in Northwest Indiana, according to ABC 7 Chicago Meteorologist Larry Mowry.

The doughnut shaped circles that expand on the radar are birds leaving their overnight roost, Mowry said.

The radar beam spotted likely thousands of birds taking off as the sun comes up this morning between 5:30 a.m. and 6:00 a.m.

Radar in Northwest Indiana detected birds taking off as sun came up Saturday morning.

These birds are most likely purple martins that tend to roost together at night and then spread out reaching higher altitudes, according to Mowry.

This species of bird tends to nest in groups near bodies of water and return to the same spot in the evening.

These type of radar signatures are sometimes spotted on summer mornings.

The radar beam usually detects rain or snow in the sky, but the beam bounces off any object in the sky and shows it to us, Mowry said. It is the same way radars track airplanes in the sky.