It's a falconry display - the birds are used for flying displays through the day; judging by the fact that we saw the smaller birds being loaded into a car at the end of the day I'd guess the birds are supplied by an outside falconry centre, which is not uncommon.
While you could debate the animal welfare implications of birds being kept this way (much depends on how often they are flown or if they move to aviaries when not 'working', to my mind), this is a pretty standard way of keeping and displaying falconers' birds.
That's fine for temporary purposes, as long as its not their permanent exhibit. I can see them being placed there for several hours between shows, but no more.
