Bird-Boy, alias Bird-Brain, was created by the mad scientist calling himself the Ani-Mator. He was created as one of gene-spliced animal/man hybrids. The crazed Ani-Mator was a scientist working for the paramilitary and anti-mutant organization, the Right, supposedly on a project to halt and reverse mutation, but actually was working to create a pool of "Ani-Mate" slaves for mankind. Bird-Boy, like many of the Ani-Mates, was intelligent and resented the torture and barbaric training of the Ani-Mator.
Soon, Bird-Boy escaped the Ani-Mator's laboratory/island. He was captured and placed on display as a freak of nature in New York City, where he was inadvertently freed by the young mutant Cannonball. Cannonball's team, the New Mutants, later spotted Bird-Boy on the television news, and tried to capture him for their school, Xavier's School for Gifted Youngsters, in order to help him. The New Mutants fought their counterparts, the villainous Hellions, and took Bird-Boy back to their school without telling their current headmaster, the mutant Magneto. Eventually, the mutants convinced Magneto to let Bird-Boy stay with them.
Bird-Boy created chaos by going into public, however, and was grounded at the school. Instead, he escaped to try to rescue other Ani-Mates. The New Mutants followed and helped Bird-Boy free the Ani-Mates, defeat the Right, and imprison the Ani-Mator in the extradimensional world of Limbo.
Bird-Boy assumed leadership of the Ani-Mates, and began to teach them about civilization and what it means to be human.
De-evolved to an actual condor by the Sphinx, Condor was found by Bird-Brain. Sensing intelligence inside the bird, Bird-Brain used the Ani-Mator's machines to re-evolve Condor.