A breeding colony, or  ternery, exists on Mud Islands where each summer about 1,500 pairs nest in a compact group, each bird is scarcely out of pecking range of the ones adjacent to it. This give some level of protection against predatory gulls that snatch eggs and young wherever possible. It feeds on small fish that are caught by diving from 5m or more. Usually seen in small flocks, terns often congregate on the rocky platforms or beach when not feeding.