Readers who worry that there's something nefarious afoot in the multiple reported bird die-offs in the nation this past week can take heart. There's actually excellent historical evidence that this sort of thing happens all the time, according to Randall Cerveny, a professor of geography at the School of Geographical Sciences & Urban Planning at Arizona State University in Tempe.

"Massive bird falls have long been noted," he tells USA Today. Here he lists 12 over the past century:

1. Baton Rouge LA: July 1896:

On Friday morning last early risers in the little capital [Baton Rouge La.] witnessed a peculiar sight in the shape of a shower of birds that fell from a clear sky, literally cluttering the streets of birds that fell from a clear sky, literally cluttering the streets of the city. There were wild ducks, catbirds, woodpeckers, and many birds of strange plumage, some of them resembling canaries, but all dead, falling in heaps along the thoroughfares, the singular phenomenon attracting many spectators and causing much comment.

The most plausible theory as to the strange windfall is that the birds were driven inland by the recent storm on the Florida coast, the force of the current of air and the sudden change of temperature causing death to many of the feathered creatures when they reached Baton Rouge. Some idea of the extent of the shower may be gathered from the estimate that out on National Avenue alone the children of the neighborhood collected 200 birds.

2. Worthington MN, March 13, 1904: 750,000 Bird Fall.

"Roberts tells the fate of migrating Lapland Longspurs on the night of March 13-14, 1904 which 'was very dark but not cold, and a heavy, wet snow was falling with but little wind stirring. Migrating Longspurs came from the Iowa prairies in a vast horde, and from 11 P.M. until morning, incredible numbers met their deaths in and about villages by flying against buildings, electric light poles and wires, and by dashing themselves forcibly onto the frozen ground and ice.' In Worthington, Minnesota, an attempt was made to compute the numbers lying dead on two lakes with an aggregate area of about two square miles. 'A conservative estimate showed that there were at least 750,000 dead Longspurs lying on the two lakes along!' The total area on which dead migrants were found covered approximately 1,500 square miles."

The reality, say biologists, is that these mass die-offs happen all the time and usually are unrelated.

Federal records show they happen on average every other day somewhere in North America. Usually, we don't notice them and don't try to link them to each other.

"They generally fly under the radar," said ornithologist John Wiens, chief scientist at the California research institution PRBO Conservation Science.