the owlery,

The Owlery is a room on the top of Hogwarts Castle's West Tower, where the school owls and the owls belonging to students live during the school year. The Owlery is a circular stone room, rather cold and drafty, because none of the windows had glass in them. The lack of glass on the windows allow the owls to come and go freely. The floor was entirely covered in straw, owl droppings, and the regurgitated skeletons of mice and voles. Many owls were nestled here on perches that rose right up to the top of the tower. During the winter months, the room is very cold, to the point that one has to be careful with ice on the higher landings.