Millions of Michigan's birds have either started making the trek south for their annual fall migration to warmer winter destinations or they are about to.
About 3.8 million birds will fly southward over Michigan Monday night, Aug. 31, according to Purdue University's AeroEco Lab.
The BirdCast Migration Dashboard, a live migration map provided by Cornell University's Lab of Ornithology, says Michigan's fall migration is reaching its peak time frame — from mid-September to mid-October. Overall, about 170 million birdsare expected to be in flight overnight Monday into Tuesday.
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 W. Rose Postdoctoral Fellowship, and Amazon Web Services, the National Science Foundation and Leon Levy Foundation.
Want a closer look? Shop binoculars here
Here's what to know about fall bird migration.
How many birds will fly over Michigan tonight?
About 3.8 million birds are expected to fly over Michigan Monday night, Aug. 31, as part of fall migration, according to Purdue University's AeroEco Lab.
The estimate is about 4.2 million birds on Tuesday and more than 6 million on Wednesday night.
The Lab says peak traffic will be taking place in the western Upper Peninsula where the highest level of "lights out" alert status has been issued. The rest of the U.P. is is the medium lights-out range.

When is fall bird migration season?
In Michigan, fall bird migration is generally takes place between Aug. 1 and Nov. 30, BirdCast says.
Peak migration is defined by the seasonal window during which about 50% of nighttime bird migration traffic passes through an area.
According to the Birdcast historic track, Michigan migration season peaks in late September and early October.
The dashboard notes that numerous species of warblers are most likely to be migrating at this time.
How can you track bird migration south?
CornellLab hosts a BirdCast Migration Dashboard that provides daily summaries of radar-based nocturnal bird migration. With it, you can watch the progress of birds as they make their way south across the nation and even track how many flew over your county the night before.
How do I know when birds are flying through my area?
BirdCast provides live and local bird migration alerts throughout the continental U.S. by employing real-time analysis of bird migration traffic as detected by radar.
You can use the tool to determine whether birds are migrating in your area in low, medium, or high densities by entering your city in the search field on the website.
Where are Michigan birds flying to?
During fall migration, various species of birds depart Michigan and fly southward — as far as Central and South America, Cornell University says.
How can you help birds migrate?
To aid birds as they migrate, ornithologists urge Americans to turn off nonessential lighting — going "lights out" — from 11 p.m. to 6 a.m. during peak migration periods. Bright lights can attract and disorient birds that migrate at night, potentially causing fatal collisions with buildings.
Contact Jenna Prestininzi: jprestininzi@freepress.com.
This article originally appeared on Detroit Free Press: Michigan bird migration underway. Heavy traffic expected in U.P. Monday
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