Indeed, not to say that "something" isn't going on, but I wonder how many dead fish and birds we'd find if we were at ZOMG-Defcon1 all the time and actively LOOKING for them.
Correlation not equaling causation, and all that.
Plus, all the birds going nuts and migrating at odd times, or going nuts and flying into windows etc. is a pretty standard trope for the opening sequence/foreshadowing of disaster movies over the past decade or so. So it's kind of a mental fixture in many people's minds, and subject to having greater significance than the event really has being assigned in people's minds.
And the fireworks/thunder thing is plausible to me, as much as anything else. My mother and uncles used to amuse themselves by hypnotizing the chickens on the family farm in the 1950's. They'd take a piece of feed pinched in their fingers and slowly move it back and forth until the bird was out of it, and they could even lay the bird on it's back in their hands. They'd then leave it there, and it would take 10-15 minutes and suddenly come to.
One day they did this, and three days later the chickens they'd hypnotized all died. Grandpa was pretty pissed.
Also thinking about how dolphins/whales can get confused and beach themselves etc. too.