The feathers of birds, collectively called plumage, play several roles. Brightly coloured plumage, sometimes including ornamental feathers called plumes, is often influential in attracting a mate, but display of such plumage is used with equal frequency by males to try to intimidate other males competing for females or for territory. Some birds are camouflaged to resemble their surroundings, thus escaping the notice of possible predators (see camouflage). They sometimes even adopt a pose that enhances the protective coloration. The marsh-dwelling herons called bitterns “freeze” with their striped necks and long bills pointing straight up, emphasizing their resemblance to the surrounding reeds. .