Yes indeed, I believe they were kept in there to deter pest species which were a problem, they did have free-flight in the large walk-through. However they were not kept in there for long.
Thanks temp and Nanook, I don't think I've seen many walkthroughs with raptors, although I know of a couple of "walk-ins" with some species, including rescued Bald Eagles. I guess these were removed because they would have preyed on chicks if there were any in the Snowdon?