Just before Thanksgiving, there was an unusual shower in Cumberland County, New Jersey. Somewhere around 200 red-winged blackbirds died suddenly and rained from the sky, littering the ground in a small rural community.

Now it's more than a month later, and state environmentalists still don't have an explanation for what caused the birds to plummet to the earth, despite conducting a battery of tests, reports the Press of Atlantic City.

The deceased birds were found in a housing development surrounding by massive farm fields. Less than a month earlier, a few dozen dead birds were found in the same area. Several months before, a similar situation occurred in another New Jersey farming community.

No obvious cause found

"Laboratory testing did not find pesticides that are typically used in nuisance bird control or other common pesticides," Larry Hajna, a spokesman for the New Jersey Department of Environmental Protection, tells MNN. However, the state cannot rule out pesticide poisoning "due to the highly localized nature of the die-offs," he said.

Wheat seed had recently been planted at a nearby farm, but no chemicals were detected during testing, even though it had been treated with three fungicides and one insecticide. Those compounds are not considered highly toxic to birds, according to the Press, so they likely did not cause the deaths.

"Additional testing also concluded that the birds likely did not did not die from infectious disease," Hajna said.

When necropsies were performed on the birds, the lab found trauma and internal bleeding from the birds hitting the ground, but no obvious signs of chemical poisoning or other possible causes.

Because the population of red-winged blackbirds is considered robust by the federal government, they are exempt from protections awarded to other migratory birds.

According to the Press, it's legal for farmers and landowners to poison blackbirds, cowbirds, crows, grackles and magpies "if they damage crops or livestock feed, cause a health hazard or structural damage, or to protect an endangered or threatened species." Habitat loss is typically a greater concern to bird survival than die-offs, say birding experts.

Locals, however, are baffled by this particular mystery and would like an explanation.

"Out in the country like this, you find dead stuff lying around all the time . . . but this was kind of weird," resident Debbie Hitchner told the Philadelphia Inquirer after finding six of the dead blackbirds in her backyard. "My dog just kept finding them, one after the other."