What's Up? Deaths of Thousands of Black Birds in Arkansas?

We are wondering about the black birds falling from the sky.  Has some new death ray been created that kills dark colored creatures?  Was some sort of wide-field laser used to down the flock? About 4,000 red-winged blackbirds fell from the sky dead on New Year's Eve near Beebe, Arkansas. The birds fell in an area about a mile long and a half-mile wide. An aerial survey indicated that no other dead birds were found outside of that area.

It is being speculated that the flock could have been hit by lightning or high-altitude hail, or may have been startled by fireworks.  Although some are saying that such bird deaths are not unusual, we have never heard of such an incident before.  Anywhere.