Pigeon Pete was created by Old Hob using some of the mutagen that created him in order to begin building his mutant army.
Vs. Rocksteady and Bebop
Pete is later sent off by Hob to find some more animals from the pet shop for mutation. He instead gets the idea to find real mutants and stumbles into Rocksteady and Bebop. He explains to them Hob's plan for a mutant army even mentioning that there are "turtles" in their army. Rocksteady and Bebop then decide to investigate to continue their feud with the Turtles on behalf of the Foot Clan.
Rocksteady and Bebop attacks the combined forces of the Turtles and Hob's gang, which results in Pete running away and hiding. He soon appears to rescue Raphael and Alopex whom are tangled up in a pigeon coop on a rooftop after being thrown there by Rocksteady. Pete returns to the site of the battle after it's over begging Hob not to throw him out of the mutant army; and he's quickly forgiven.
Pete hasn't displayed any sort of powers or even skill at the moment. He's very friendly to everyone but not very smart in the least, and he loves to remind folks his name. Old Hob usually calls him every name in the book related to being stupid.