Authorities say that a legally applied pesticide is to blame.
Residents of Millville saw birds - mostly red-winged blackbirds buts also some sparrows - falling around 8:30 a.m.
Police responded to calls by using a reverse 911 system to tell people living on a few streets to stay inside while they figured out what was going on.
Cumberland County spokesman Troy Ferus told WPVI-TV that county officials traced the deaths to Avitrol, a chemical that suppresses a bird's nervous system. Ferus said the farmer, who was licensed to use the chemical, acknowledged spraying the pesticide Monday.
Michelle Cavalieri told The News of Cumberland County that it was like a horror movie. Birds would fall, try to get up and fall again until they could not move at all.
Darlene Knoll said she saw birds fall to the ground off a feeder.
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