Grand Marais, Minn. – The Minnesota DNR recently collected 50
dead birds that were floating 200 to 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 would not affect such large numbers over such a
short time span. Pollution or contaminant exposure is not a likely
cause of this mortality, because of the lack of any identifiable
Why the birds ended up in the water is a mystery. It is known
that they cannot recover from landing in the water. Early morning
winds were about 16 mph from the northwest, but there were strong
gusts to 40 mph before the wind suddenly switched to the southeast
at 9 mph. Apparently a “lake effect” wind event occurred in the
early morning hours that caught the migrating birds.
“If the extent of the mortality is not vastly greater than that
indicated by these collections, the effect on bird populations is
not significant,” Ingebrigtsen said. “Passerines migrating through
Minnesota number in the hundreds of thousands. Any large bird kill
is concerning, however, because studies have documented a long-term
decline in many passerine species.”
Officials say the birds may also have been caught over the lake
in the high winds, and just could not make landfall.