Let's list where all these events occurred and causalities first:
Beebe, Arkansas - 5000+ birds dead
Baton Rouge, Louisiana - 500 dead birds
Falkoping, Sweden - 100 birds dead
Kentucky - X00+ birds dead
Little Bay and Waikawau Bay, Coromandel Peninsula, New Zealand - X00+ birds dead
Thanet, Kent, England - 40,000+ dead crabs
Chesapeake Bay, Maryland - 2,000,000+ dead fish
Coast of Paranaguá, Brazil - Just said 100+ tons of fish
Port Orange, Florida - X00+ dead fish
Just for the sake of visuals, here are all the places these events are popping up:
[image width=750]http://www.zerohedge.com/sites/default/files/images/user5/imageroot/havenstein/Birds_0.PNG[/IMG]
Lighting/toxins - Likely not. Birds get hit by lightning very rarely, let alone in mass, and toxins would affect far more than 1-4 species of fish and sealife.
Honestly, looking at all the data, I would pin this on an act of nature. We've had record low temperatures around the world this last year, so bitter cold can be one factor.
The second theory is an infection, but having that many in such a short time die is beyond weird. It would have to impact a large mass that traveled together for a time, and then killed them all within a very narrow period of time. Even the Black Death didn't do that overnight.
The third theory is divine intervention or a sign thereof. (I'm Lutheran, just as an advance notice.) Now, one of the original plagues was indeed the death of all of Pharaoh's livestock within days, however from the species of fish/birds/crabs listed, in the world, they far outnumber the number of cattle and other farm animals the Egyptians had.