In the Harry Potter movies, was their a specific owl, or owls that played Hedwig? What are their name/names and in what movies did they appears?
There were actually at least eight different animal actors used to portray Hedwig throughout the Harry Potter movies, but Gizmo seems to have been the primary animal actor.
Seven were needed to play Hedwig, the owl Hagrid purchased for the young wizard prodigy: named Gizmo, Kasper, Oops, Swoops, Oh Oh, Elmo and Bandit.
This other article mentions an eigth - White Terror Of The North. Why he was not mentioned in the other article is not clear, but he did not appear in The Sorcerer's Stone.
He starred in all the Harry Potter movies but the first
This same article mentions that there were nine owls used, but does not identify the others by name.
He was the more enthusiastic of the 9 owl actors that played Hedwig
The book The Animal Movies Guide mentions that Gizmo was the primary animal actor during The Sorceror's Stone.
Harry's own owl familiar is a snow named Hedwig, who was played mainly by Gizmo (Gizmo was doubled by Kasper, Oops, Swoops, Oh-Oh, Elmo, and Bandit).
Q: For Harry's owl—Hedwig#151how many owls played Hedwig, or did you use just one?
Gary: There really is just one Hedwig—his real name is Gizmo. He has a couple of helpers that help him out with the different things. We have a lighting stand-in, so he doesn't have to do all of the lighting. And we have a couple of owls that will help him with his flying shots, so he doesn't have to do all of the flying shots himself.
HP Wikia mentions the possible ninth owl, Sprout, but the linked source does not actually make any mention of an owl by that name.