Why are thousands of dead birds suddenly falling from the sky?S

This week, 5,000 blackbirds fell from the skies over Arkansas, followed by 500 more in Louisiana. And now it's happening in Sweden too. You've got to wonder what the hell is going on. We'll explain.

Let's quickly review the facts. Just before midnight on New Year's Eve, anywhere from 1,000 to 5,000 red-winged blackbirds and starlings fell from the sky within a one-mile area over the town of Beebe, Arkansas. The last few days have also seen a mass fish kill, in which an estimated 100,000 drum fish washed up on a twenty-mile stretch near the town of Ozark, Arkansas, which is about 125 miles away from Beebe.

And then, around 500 red-winged blackbirds, starlings, and grackles fell to their deaths over a quarter-mile stretch of highway near Labarre, Louisiana, which is 360 miles from Beebe and 450 from Ozark. And then last night, hundreds of what were most likely jackdaws fell to the ground all over Falköping, Sweden.

So, now that we've got all the facts, what on earth is causing all these animals to die?

Some of the more fanciful interpretations have put these forward as signs of the Apocalypse, undoubtedly as the first act of some macabre play of bizarre death and destruction that will end in December 2012. But there are perfectly rational explanations for all of this. Still, I'll warn you now - the explanations might be scientific, but they're not exactly likely, and they sure as hell aren't elegant or logically pleasing.

Why are thousands of dead birds suddenly falling from the sky?S

The first thing to understand is that there isn't one single cause for all this because this isn't one connected event. These are completely separate events that are, according to all experts and investigators, entirely unrelated. Indeed, there's no great mystery behind the 100,000 dead fish. The fact that only drum fish died means the cause of death was localized in a specific species, which rules out pollutants or toxins. Some as yet unidentified disease killed the fish, which is something that happens from time to time. This particular fish kill is more severe than most, to be sure, but it's still not unprecedented.

The birds are a little more complicated. We're still waiting on analyses of the dead birds that will solve the mystery, but there are already several theories to account for the deaths. So far all we know for sure is that the Arkansas birds showed signs of blunt-force trauma, although it's possible that was just caused by slamming into the ground.

Why are thousands of dead birds suddenly falling from the sky?S

Weather could be the culprit. High-altitude hail or lightning might have hit the birds, which caused them to fall from the sky. Arkansas Game and Fish Commission ornithologist Karen Rowe says a severe weather system did move through Arkansas on New Year's Eve, so it's not impossible. The only problem is the birds don't seem to have any of the telltale bruises or injuries that a weather-related explanation would cause.

Thankfully, we can probably rule out disease and toxins. Arkansas experts say a disease would take down a lot more than just one isolated flock - and no, the second group of dead birds in Louisiana isn't enough to make disease seem like a viable possibility. The same thinking goes for poisoning - if that were the case, birds would be falling all over Arkansas, and that just isn't the case. The Arkansas Department of Environmental Quality tested the area for any air toxins, but the skies are officially clean.

One thing to remember is what day and time the incident occurred: near midnight on New Year's Eve. Plenty of people mark the beginning of the new year with fireworks, and it's possible these celebrations caused this nasty accident. Arkansas Game and Fish Commission spokesman Keith Stephens says the commission currently favors this theory, as fireworks that were shot off in just the right area near the birds when they were roosting could have scared them, creating a traumatic stress event.

Why are thousands of dead birds suddenly falling from the sky?S

Obviously, birds don't usually fall from the sky when fireworks are shot off, so what would have happened here? We do know that birds tend to be more highly concentrated in rural areas, meaning one big fireworks blast in just the wrong area would have terrified thousands of birds all at once.

This would have happened at night, when birds are roosting on the ground - and if this did indeed happen when the birds were asleep, experts say the trauma would have been enough to kill them, as the terrified birds frantically flew into each other in the heavy night fog. Witnesses have since come forward to say they saw a person setting off industrial-grade fireworks near the roosting area, which would seem to back up that theory.

For what it's worth, a lot of Beebe residents don't buy that theory, saying they've shot up plenty of fireworks before and nothing like this has ever happened. That might well be true, but the thing is that whatever caused this was staggeringly unlikely, and that all of the theories require a very unlikely confluence of factors. That's the problem with vastly improbable events - their explanations don't tend to be terribly logical.

So then, the fish were done in by disease, and the Arkansas birds were probably killed either by a freak weather event or some fireworks. That leaves the birds in Louisiana and Sweden. This is where those who like their explanations to be neat and tidy are probably going to be less than thrilled...because these things almost certainly had nothing to do with either of the other two events.

Why are thousands of dead birds suddenly falling from the sky?S

Officials with the Louisiana Department of Fisheries and Wildlife have stated that many of the 500 birds found near Labarre had broken beaks and wings, along with other signs of violent injury that probably weren't simply caused by hitting the ground. In all likelihood, the birds hit some power lines while flying at night, which can occasionally happen because blackbirds and starlings don't have particularly good night vision.

So that's that then...or it would be, if yet another bird death event hadn't happened last night in Sweden. Again, it is unusual for this to occur, particularly so soon after two other similar incidents. Still, once again the causes themselves don't seem to be all that hard to work out - the birds were likely traumatized by an unusual event, much like the Arkansas blackbirds and the fireworks. It's strictly the timing of all this that is weird.

Indeed, this whole thing is odd. It is sort of hard to accept that three freak events occurred in a 500-mile area within five days of each other...and it really was just a weird coincidence. Fish do sometimes die off, and 100,000 dead isn't all that unusual if a particularly virulent disease hits. Blackbirds and starlings sometimes hit power lines when they're flying at night, which can then cause mass chaos in their flock that can leave hundreds of birds dead. And, though it's slightly less common than either of those two events, birds can every so often be so terrified by loud fireworks that the entire flock suffers a catastrophic stress event.

Is any of this likely? Absolutely not. But that's the fun thing about living on this planet (well, unless you're a blackbird or drum fish) - if you wait around long enough, deeply improbable things will eventually happen. And this is all very definitely deeply improbable.

Previously on io9:
Over a thousand dead black birds rain down on Arkansas town
100,000 fish wash up 100 miles away from massive bird die-off
Hundreds of dead black birds rain down from the sky in Louisiana
Taiwanese news coverage of the Southern USA bird die-offs is expectedly deranged