There are high poles in the orang-utan enclosure and as it was the end of the day, the gulls were looking for somewhere to perch on. They were playing a kind of "king of the castle game". Despite the low light and very dull sky I managed to take this picture which shows the details of the wings of the gulls.
Location: Twycross zoo, Leicestreshire, UK
Photographer: Arnaud Germain