The Gunnison grouse or Gunnison sage-grouse or lesser sage-grouse (Centrocercus minimus ) is a species of grouse endemic to the United States. It is similar to the closely related greater sage-grouse (Centrocercus urophasianus ) in appearance, but about a third smaller in size, with much thicker plumes behind the head; it also has a less elaborate courtship dance. It is restricted in range to southwestern Colorado and extreme southeastern Utah, with the largest population residing in the Gunnison Basin region in Colorado. Despite being native to a country where the avifauna is relatively well known, it was overlooked until the 1990s due to the similarities with the sage grouse, and only described as a new species in 2000—making it the first new avian species to be described from the USA since the 19th century. The description of C. minimus as a separate species is supported by a molecular study of genetic variation, showing that gene flow between the large-bodied and the small-bodied birds is absent.
The Gunnison sage-grouse is an endemic grouse of the United States. It was not recognized until 2000 as a different species to the greater sage-grouse. The Gunnison sage-grouse is smaller, and the male has a stronger banded pattern on its tail feathers. It is a large bird that has a small head, a chubby, round body, and a long tail. A male changes his shape dramatically when he displays, becoming almost spherical as he puffs up his chest, droops his wings, and fans his tail into a starburst.
These birds are found in south-west Colorado in the Gunnison Basin in the Gunnison and Saguache counties, and there are further small, fragmented populations within Colorado and a further one in south-east Utah. These birds inhabit sagebrush plains. They occur on open plains and in high valleys, only in the vicinity of sagebrush. Their prime nesting habitat includes lower wet areas where the young are able to forage for insects.
The Gunnison sage-grouse is a social bird that travels in flocks and spends most of its time preening, stretching, and feeding. The day begins with foraging, then it rests until twilight, when it begins looking for a place to shelter and roost. Sage grouse seem to spend 60% of their day foraging. They are considered sedentary, but will travel long distances seeking food or shelter. In winter, flocks are segregated according to gender, and sometimes they roost together in the sun to get warm. Flocks reunite in the spring, the males strutting and setting up territories to attract females. In summer, once most of the eggs have hatched, hens and chicks will forage together. Sage grouse can fly well, despite their heavy bodies, and flying is a good response to danger, as their short legs mean that they cannot run fast.
Gunnison sage-grouse are omnivores, they feed on forbs, leaves, buds, flowers, beetles, ants and grasshoppers. Where habitats are fragmented, they forage and roost in fields of alfalfa, beans and wheat.
Gunnison sage-grouse have a "clumped polygyny" mating system where multiple males are in competition to mate with females in an area called a lek. From mid-March to late May, many males migrate to lek sites, often returning to the same one every season. A male is very territorial and will defend his lek from intruders. Males do not participate in nesting or rearing of chicks. Nesting is from mid-April until June, after which hens may migrate some distance from the lek, seeking optimal nesting conditions. A hen produces one brood per season, laying 6 to 8 eggs that she incubates for 25 to 27 days. Chicks leave their nest soon after hatching to feed on insects. By 2 to 3 weeks old they can make short flights and are able to feed themselves. They can sustain flight by the age of 5 to 6 weeks and are independent when they are 10 to 12 weeks old. In winter, mothers and chicks separate into gender segregated flocks and may reunite in the spring when the flocks travel to lek sites. Females become mature when they are 1 year old and males at 2 years old.
The main threats to these birds are loss of habitat from human disturbance, their small population size and its structure, climate change, drought and disease. Specific threats as a result of human activity include ecologically harmful grazing practices, invasive plants, fences, changes to fire regimes, extraction of natural resources, encroachment of juniper and pinyon on sage lands, disturbance from recreation and water development.
This species has a very small occupied range. According to the IUCN Red List, the total Gunnison sage-grouse population size is around 2,500-2,600 individuals, including 1,700 mature individuals. Currently this species is classified as Endangered (EN) and its numbers today are decreasing.