By Stephen M. Silverman
Updated April 29, 2003 08:11 AM

Not surprisingly, Big Bird has a big mouth.

Actually, it’s the man behind the “Sesame Street” Bird — Caroll Spinney, 69, who’s been the overgrown fine, yellow-feathered friend for the past 34 years on the children’s show, which is an institution on PBS.

Now, Spinney’s autobiography, “The Wisdom of Big Bird,” is hitting book stores Tuesday. It’s anything but feather-brained, and Spinney — sensitive to what his young fans might think — is entering the tell-all arena carefully.

“For years I’ve kind of hidden from the public because I’ve seen disappointed kids,” Spinney tells the Associated Press from his Connecticut home.

Case in point: Spinney was once introduced to a 9-year-old neighbor who was a big fan. “He comes running in … and said, ‘Wow, where’s Big Bird?’ And (the boy was told) ‘This is the fellow who’s in it.'”

Recalls Spinney: “He looked at me and you’ve never seen such a crestfallen face.”

Spinney, who is also the voice of Oscar the Grouch, reveals that Oscar’s scratchy voice was inspired by a foul-mouthed cab driver from the Bronx.

“Some people have asked which am I most like, Big Bird or Oscar?” Spinney said. “And my wife says mostly I’m like Big Bird. But if anything can get me sounding like Oscar, it’s frustrating drivers.”