[General] Freaked out of his bird?

coolfool said:

I don't understand the following highlighted parts:

In fact, some of the things you see in the film - like my looking away and trying to keep myself from breaking up - were caused by my looking at Denis off-camera over in the bushes, totally freaked out of his bird, laughing his head off while I'm in there trying to do my Lyndon Johnson and keep everything together. - page 168, Jack Nicholson, December 2012, Playboy

I can't figure out the exact meaning of the former and guess the do of the later may mean act but ain't sure.

Please lend a hand. Thanks a lot.

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Gillnetter said:

Totally freaked out = Lost control. Acting in a strange manner. Teenagers use the term "freak out" to mean that someone, or that they, are reacting to an event in an abnormal manner.
His bird = His mind.

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