[[WMG: The lovebirds are the masterminds.]]
I've always had a theory about what caused the birds to start acting so differently: the lovebirds. Somehow they orchestrated everything - this would explain why the attack at the end seems to be concentrated mainly, if not solely, on the Brenner house.

[[WMG: Global warming was causing the birds to attack]]
Thankfully the birds did not enter the [[{{Birdemic}} exploding phase]] that global warming causes.