Michigan skies fill each night with millions of migrating birds. How to track them

Millions of birds are flocking southward across Michigan each night amid their annual fall migration , and bird watchers can track their flight live.

The BirdCast Migration Dashboard, a live migration map provided by Cornell University's Lab of Ornithology, estimates the number of birds in flight each night, highlighting the largest groups, their paths and other information.

More than 7 million birds were in flight over Michigan Thursday night, Sept. 11, according to the migration dashboard. Nationally, more than 46 million birds were in flight Sept. 11-12.

The Birdcast system uses radar because most species migrate at night, some at altitudes as high as 15,000 feet, and aren't visible to the naked eye.

Cornell Lab of Ornithology produces the maps with support from NASA, Edward