When is the climax in The Birds?

At the end of the movie, Melanie and the Brenners escape during one of the breaks between attacks.

After a terrifying night of attacks, dawn has come, and everything is quiet. Melanie, however, goes upstairs to investigate a strange noise -- which as we all know is always a huge mistake in Horror movies -- and ends up trapped in an upstairs room that the birds have managed to break into.

She is blitz-attacked by an entire flock of them and is very badly injured. Mitch saves her before she is killed, but she needs medical care. So they decide they have to risk it, and try to escape.

The birds are completely surrounding the house, but they're not attacking. They're just kind of meandering around in a restless and vaguely threatening way.

So, Melanie, Mitch, Mrs. Brenner and young Cathy creep slowly out of the house through the endless flocks of birds and into the car, and they drive away. The end.