From National Audubon Society:
A charging Stegosaurus, a bloodthirsty Indominus rex, a screeching Pteranodon, and . . . a baby pelican? The digitized dinosaurs of Jurassic World aren’t as terrifying as you might think, at least if you listen closely: Their roars, growls, and squawks are actually provided by their living descendants—birds.
“Birds are a great source for dinosaur sounds,” says Al Nelson, one of the sound designers for the film, “because they are tonal, musical, and expressive, and that is what we are always on the hunt for.”
This is something the franchise already knew well: Gary Rydstrom, the sound designer on the original 1993 version, employed several birds to voice his dinos. That Velociraptor death hiss? It’s really an irate goose.