Specimen Maintenance is an area in Borderlands 2, inside the Shipping Yard
You get sent there in the mission Wildlife Preservation
Walkthrough
Upon entering the Specimen Maintenance, Mordecai tells you that Bloodwing should be in one of these cells and not to worry about the other ones, they can't get to you. Mordecai wants you to just get Bloodwing and you'll have what you need to upgrade Claptrap and get through that Death Wall.
Go across the room and through the door that's aptly labeled "Domesticated, Extremely Dangerous - Bloodwing".
Enter Bloodwing's Enclosure