According to Wikipedia,
Species
The book
"G" is for Growing: Thirty Years of Research on Children and Sesame Street refers to Big Bird as a
canary.
[9] In an episode of
Sesame Street, Big Bird was asked if he was related to the
cassowary; he replied, "I'm more of a
condor." On the January 23, 1976 episode of
Hollywood Squares, Big Bird was asked what kind of bird he is and said he was a
lark, causing host
Peter Marshall to crack up.
[10] In the film
Don't Eat the Pictures, Osiris calls Big Bird an
ibis. Big Bird appeared in a
series 11 episode of
Mister Rogers' Neighborhood, in which he declares he is a "golden condor". Regardless, he is always described as being flightless.
So who knows, but I guess I'll have to go with CRaP...