"Boids. Dirty filthy boids."

The bird songs introduced by restorers into Vertigo's Muir Woods scene establish a refreshing outdoorsy atmosphere which contrasts with the surrounding scenes, as well as with:

Documentary Style Dialogue Biography
Redwood forests tend to stifle non-redwood life "The music and the sound effects are elusive and lonely, fragile and ghostly...." -- Donald Spoto Madeline closes the scene by begging to be taken somewhere where it's light, indicating a claustrophobic mood In interviews and in his work, Hitchcock often expressed a fear of birds
Genealogy
From the shooting script:
           MADELEINE
       (Simply)
    Knowing I have to die....
    
She looks up at him with a shy embarrassed smile.
Then, seeing the wondering look in his eyes, she
brightens quickly.

           MADELEINE
    But I like the stream! It's
    a lovely stream!

She leaves him and moves quickly out onto the
bridge and leans on the railing to watch the water
rippling below. And then, as he approaches her,
she turns and looks at him, wide-eyed.

           MADELEINE
    But it makes no sound! Listen!

She listens intensely for a long moment, and looks
at him anxiously.

           MADELEINE
    Do you hear anything?

           SCOTTIE
       (Shaking his head)
    Only silence. It's always like
    this.

           MADELEINE
       (Wondering)
    And no birds sing.

           SCOTTIE
    No birds live here.

           MADELEINE
    No.


Copyright 1998 Ray Davis
Screenplay excerpt by Alec Coppel and Samuel Taylor