Unfortunately one of the lovebirds did attack if I've heard right. One of the lovebirds attacked and killed the other lovebird during the making of the movie according to some sources.

Because they were in a cage the whole movie.
Doy.
This signature really brings the room together, Does It Not?

warn and set off other birds. I still reckon that it was that pair that stirred things up, despite there being an isolated attack in Bodega Bay before they got there.
Yeah that's what it seemed like
Donna is the only member of filmboards that nimda punished for wanting to leave.

Birds are dinosaurs. They lost their inheritance.

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They were a sleeper cell. Their scene was cut. In the car, at the end, as they drove away.the love birds made their move.
(oh god.do I HAVE to say that this was a dumb joke??? i have such little faith in humanity anymore that I'm just compelled to explain my joke. our species is doomed. Maybe the birds will inherit the earth.).

Because they were in love.

I agree and your post has given me further evidence to think so. The woman in the restaurant that accuses Melanie is in part right, but it was the Lovebirds and not Melanie that stirred the attacks. The attacks started soon after Melanie left the Lovebirds "trapped" in the cabin. Notice at the end that the birds stay calm as soon as the Loverbirds leave the cabin. It's as if the birds were rioting because their own kind (Loverbirds) are imprisoned. They calm down when they realise that the birds are released from the cabin or "prison".