Jason Coffman’s review published on Letterboxd:
Jimmy Screamerclauz's debut feature Where the Dead Go to Die was (in addition to being genuinely disturbing) technically rough, which is not surprising given the fact that he's a one-man show who basically taught himself to do the animation while he was in the process of making the film. His follow-up is still ragged around the edges, but it's a major step up on pretty much every conceivable level. When Black Birds Fly is a lot less serious than his previous film, featuring moments of effective black comedy, and he's created a fully-formed universe and mythology.
The swipes at organized religion are broad and obvious, but the specifics of the stories here are compellingly strange and much of the characterizations are convincing and poignant with great voice acting that gives the film a strong emotional anchor (just as it did in "The Masks That the Monsters Wear," the strongest segment of Where the Dead Go to Die). This is also a impressively dense assault on the senses, especially from a visual standpoint. When Black Birds Fly is packed to bursting with insane visuals that would be literally impossible to achieve in any other medium. This is a funny, creepy, unsettling film totally unlike anything else out there.