Editing Red grouse (section)

==Description==
The red grouse is distinguished from the [[willow ptarmigan]] and [[rock ptarmigan]] by its reddish brown plumage, rather than the white winter plumage. The tail is black and the legs are white. There are white stripes on the underwings and red crests above the eyes. Females are less reddish than the males and have less prominent crests. Juveniles are duller and lack the red crests.

Birds in Ireland are sometimes thought to be a separate subspecies ''L. l. hibernica''. They are slightly paler than those in Britain and the females have yellower plumage with more finely barred underparts. This may be an adaptation to [[camouflage]] them in moorland with more grass and sedge growth and less heather.

It is audially identified by its {{'}}''chut!chut!chut!chut!chut!chuttt....''{{'}} call, or the {{'}}''Goback, goback, goback''{{'}} vocalisation. The wings make a whirring sound when the bird is disturbed from a resting place.

Grouse populations exhibit periodic cycles in which the population peaks to very high densities before crashing and recovering a few years later. The main causative agent of this cyclical pattern is thought to be the parasitic [[nematode]] worm ''[[Trichostrongylus tenuis]]''.

However, in his book,<ref>Wynne Edwards, V. C. ''Evolution through Group Selection'' 1986 Blackwell Scientific Publications Oxford</ref> [[V. C. Wynne-Edwards]] suggests that the primary cause of mortality in grouse populations is [[homeostasis]], which is largely dependent on food availability, and that the 'Grouse disease', due to the parasitic worm ''Trichostrongylus tenuis'' is a misdiagnosis of the after-effects of social exclusion.