It's death on a wide scale, biblical-type stuff: Millions of spot fish died last week in the Chesapeake Bay; red-winged blackbirds tumbled from the skies by the thousands in Arkansas and Kentucky over the holidays; and tens of thousands of pogies, drum fish, crab and shrimp went belly up in the summer in a Louisiana bayou.

For an explanation of these mysterious events, some have turned to Scripture or to the Mayan calendar, which suggests the world will end in 2012. But wildlife experts say these massive wildlife kills were not the result of a man-made disaster or a spooky sign of the apocalypse.

They happen in nature all the time.

In Arkansas, state and federal biologists say they think that sleeping birds probably heard a loud boom in the night and freaked out. In Louisiana, low-oxygen ocean water regularly creeps into the higher-oxygen bayou and suffocates fish and crustaceans.

Maryland wildlife biologists are still investigating the deaths of 2 million spot and some croaker, also known as drum fish. But they have a theory: These fish are particularly vulnerable to cold and were killed when water temperatures dropped suddenly and sharply in late December. Most of the dead were juveniles.

"It's colder than it's been in 25 years," said Dawn Stoltzfus, a spokeswoman for the Maryland Department of the Environment. That's terrible news for the spot. In 1976, 15 million were killed during a cold snap.

The department's phones started ringing with reports of dead fish two days before the new year and haven't stopped. "The first ones we heard of were in Calvert County. Then some big ones over the last weekend in Annapolis and Kent Island. It could be over. It's too early to speculate," Stoltzfus said.

The state doesn't bother to clean up. Nature takes its course when fish wash up on shore, which began to happen Thursday, or birds pluck them from the water. "The best thing to do if you come across them is to not touch them, and bury them," Stoltzfus said, in advice to bayside residents.

In Arkansas, "5,000 birds falling dead in people's yards is just weird," said Kevin McGowan, an ornithologist at the Cornell Lab of Ornithology. "But the question is, has this happened before?"

The answer is yes, "but probably in a cornfield. And foxes ate them all," McGowan said.

"All birds die," he continued. "You rarely see them for several reasons. They're usually alone. They're often eaten by the thing that killed them, or they go to some sheltered place to die. You rarely see dead birds until they whack into your window."

When birds fall out the sky and fish float to the surface as if in a nightmare, people reach for an explanation. At least one Internet blogger cited the Mayan calendar, and another turned to the doomsday prophecies of Nostradamus.