A 1981 episode of the PBS television program “Mister Rogers’ Neighborhood” suggests otherwise. When Big Bird visited the Neighborhood of Make-Believe on the show, he told the character X the Owl he was a golden condor, a fictional bird species. Later in the episode, the character King Friday XIII asks Big Bird if he’s related to the cassowary. Big Bird tells the king he’s more like a condor.
The “conflict” over Big Bird’s species stems from two mediums: print and television. In his book “Sesame Street Unpaved: Scripts, Stories, Secrets, and Songs,” David Borgenicht lists Big Bird’s scientific name as Bigus canarius. The name would presumably translate into the pseudo-English phrase “Big canary.”