About 500 dead birds were discovered in Louisiana this week and 5,000 in Arkansas at New Year, many of them red-winged blackbirds. Swedish authorities have been investigating the deaths of 100 jackdaws found in a street in Falkoping.
"We made an autopsy on five of the birds yesterday and found internal bleeding but no external lesions," said Marianne Elvander of Sweden's National Veterinary Institute.
Read more: [link to www.foxnews.com
Shreveport LA, March 20, 1941:
Associated Press: Blackbirds by the hundreds dropped dead from the sky at Barksdale Field. They cluttered the army airbase so thickly that its police were called out to clear the ground. A soldier said that large flocks of the birds broke flight suddenly and plopped to the ground. Some of the dead birds were taken to the post hospital, where surgeons began autopsies."
New York City NY, September 11, 1948:
Thousands of birds (of various species) were killed when they crashed into the Empire State Building in New York City and into the transmitting tower of Radio Station WBAL in Baltimore. In this case, "there was no fog and weather conditions were good during the night and morning."
Warner Robbins Air Force Base, Georgia, October 7, 1954:
50,000 birds, representing 53 species littered the runways of Warner Robbins Air Force Base south of Macon, Georgia.
"On the night of October 7-8, 1954, the largest recorded ceilometer kill in history occurred at Warner Robbins Air Force Base, a few miles south of Macon, Georgia. It involved 53 species and an estimated 50,000 birds, 2552 of which were examined... An advancing cold front in autumn is believed to have precipitated these mass mortalities by bringing together adverse weather conditions (especially a lowered cloud ceiling), nocturnal migrants, ceilometers and/or all obstructions."
Eau Claire, WI, September 20, 1957:
According to Charles Kemper, a local bird watcher in Eau Claire, Wisconsin, the largest single killed ever recorded was a 20,000 bird fall discovered on September 20, 1957. The article suggests radio towers as the cause.
[link to content.usatoday.com
Just a small sampling, all seem to implicate electromagnetic waves.