While observed on the zoo grounds, these are not captive vultures. The Elmwood Park Zoo, somewhat notoriously, is known to attract large flocks of black vultures. Zoo staff have started to install fake, vulture-like stuffed carcasses around their usual hangouts to dissuade them from roosting, but the vultures don't seem bothered all that much. For what it’s worth, the captive bald eagles don’t seem to mind their company, but I have seen them harass a poor capybara who was just trying to take a nap.
