Last fall, the Minnesota Department of Natural Resources (DNR)collected 50 dead birds that were floating 200-800 yards from shore in an eight-mile stretch of Lake Superior between Grand Marais and the Brule River mouth.

The birds were migrating passerines (songbirds), primarily Swainson’s thrushes, white-throated sparrows, and various warbler species. Record numbers of passerines were reported at Hawk Ridge in Duluth on Sept. 7.

The birds will be examined to determine if they exhausted their fat reserves, but disease is not suspected.

“Apparently, the bird kill was caused by a weather phenomenon,” said Dave Ingebrigtsen, DNR’s wildlife manager in Grand Marais. “A disease outbreak, pollution, or contaminant exposure are not a likely cause of this mortality.”

Why the birds ended up in the water is unknown, but they cannot recover from landing in the water. Gusting winds, perhaps with downdrafts, may may have driven the migrating birds into the water or prevented them from reaching the shoreline. Although it was locally significant, the kill probably did not affect songbird populations.