Every August thousands of purple martins roost and feed in Nimisila Reservoir—one of 13 bodies of water that make up Portage Lakes, known among wildlife enthusiasts for great fishing and bird watching.
On Friday, the purple martins showed up on the radar. At a quick glance, their presence looks like rain.
Purple Martin Roost Rings showing up on radar. This is the area of the Nimisila Reservoir. This is caused by thousands of birds taking off at the same time. pic.twitter.com/jDDJuV2ZLE