Condor was an alien bird-man who teamed up with Diamondhead to fight Sphinx, lost the battle, and got turned into a real bird. Bird-Brain was a mutant who also got turned into a bird for various reasons. In some prior issues of this series, we’ve seen some birds talking about becoming people. This issue is the big reveal that they were Condor and Bird-Brain.
As revenge for Nova’s role in the Sphinx conflict, Condor goes after the people Nova loves. Nova gets him to stop.
At the end, we see that Sphinx was watching and plans to attack The New Warriors in issue #47.