Most of the US is uninhabited, so normally when these things happen, nobody notices, except maybe a farmer. The bird carcasses are quickly consumed. It's like it never happened, regardless of how large the flock of birds happened to be. This time of course, a very large flock of blackbirds met an unexpected end, and it just happened to be right over town, so lots of people were disturbed, making an interesting story for the media.
As with any such story, once it goes big, the media gets a taste for it and becomes hyper-sensitive, and will willingly report on any related topic, no matter how small, even up to the national level.
Thus the "dead birds" stories begin to show up:
(WDRB Fox 41) -- A Paducah television news station is reporting that a Gilbertsville, Ky. woman has found dozens of dead birds in her front yard. ...
Four days after an estimated 4000-5000 redwiged-blackbirds fell from the sky in Beebe, Ark., approximately 500 more dead birds were found lying lifeless on a quarter-mile-long stretch of highway in Pointe Coupee Parish in Louisiana ...
Between 50 and 100 black jackdaw birds were found dead by police in the snowy residential streets of Falkoeping, Sweden this week, mirroring the New ...
The problem here is that if the Beebe incident had not happened, then these other stories would barely have made the news. But suddenly every single little bird death is mentioned like it's part of a pattern. This repetition is self-reinforcing, and makes the press and the public even more hyper-aware of dead birds, and it gets to a stage where saying "it's normal" has no effect.
To some degree those writing the stories are aware of this, so you get odd contrast within the story, like:
Mass bird deaths aren't uncommon.
Beebe is 300 miles to the north of Point Coupee. So the likelihood of it being a related cause like poisoning is very small. If there was one source of poisoning, then the birds would all be dead in one place. If there was a widespread source of poisoning (like, as some have suggested, being sprayed from planes as "chemtrails"), then there would have been widespread carnage.
The only commonality between the two locations (and the KY incident is not worth much discussion, as it's almost certainly an overreaction to normal dead birds) is the weather. It's been pretty cold down in LA, dropping to below freezing overnight on Jan 3rd. The cold conditions were also repeated in Beebe, where it was below freezing on the night of Dec 31st.
So, we've got two mass blackbird deaths, and the media is acting like it's the end of the world, every time someone finds a few dead birds in their back yard then the local media is going to send round a news crew. But really - is it that unusual?
“These large events do take place,” he said. “It’s not terribly unusual.”
The USGS National Wildlife Health Center tracks events like these. You can see similar events on their Ongoing Mortality Events page, and the Quarterly Reports. You'll see things like in 1999, 27,000 blackbirds (and other birds) were found dead in a field in a poisoning incident. There's are several cases where hundreds of red-wing blackbirds were found dead with no cause. But if you read through the reports, you'll see there are lots of reasons why birds die.
Some people are going beyond birds and now every single mortality event gets blown out of proportion, like some sign of the apocalypse. It's just things dying, lek they do. Here's the USGS map of current mortality events. These things happen all the time, they just don't make the news, because they are normal.
Some more facts: