From Batman to Birdman to the Vulture, Michael Keaton has had a long career in Hollywood spreading his wings as costumed capers. But, in an exclusive visual effects breakdown of Spider-Man: Homecoming, which hits Blu-ray on October 17, the people responsible for turning Keaton into the Vulture reveal that they didn’t actually reference any birds throughout the movie’s complex post-production process.

In a clip premiering exclusively on Inverse, the film’s VFX team, Sony Imageworks, explains that actual jetpacks and flight suits were the primary references for the Vulture instead of badass birds of prey. “You might think that for a character like this, we might use vultures or condors for reference. But Marvel and Columbia needed him to be heavy, mechanical, inspired by steampunk aesthetic and military design,” the VFX team explains in the clip.

“So we looked at jetpacks and flight suits, seeing how actual people fly using metal machines. We saw that the jiggle and shake was less predictable than you might think.”

VFX supervisor Theo Bialek also discusses how Vulture was made into such a unique villain in all of the Marvel Cinematic Universe. “Spider-Man is fast and agile, wheras the Vulture is more heavy and powerful,” Bialek says. “The metaphor that we were using was Spider-Man is the rapier to the Vulture’s broadsword. He’s just too heavy to move fast, and that was really useful in keeping him grounded and feel real.”

Check out the exclusive clip above.

Spider-Man: Homecoming is available now on Digital HD and will be released on Blu-ray and 4K on October 17.