Stephen King's The Mist Wiki has a more comprehensive article on the same creature. For it, see http://stephenkingsthemist.wikia.com/wiki/Pterobuzzard
Pterobuzzards are vicious, extradimensional beings who inhabit The Mist.
Albino, nocturnal pterosaur-like creatures from another dimension (possibly Todash space), which pluck the aforementioned fly creatures off of the store windows. One enters through a hole in the store's display window and kills a man named Tom Smalley. The creature is then killed by David Drayton.