Centrocercus minimus

Geographic Range

Gunnison sage grouse are native to North America, and are found in southwestern Colorado and southeastern Utah. However, population distributions have been declining rapidly due to habitat destruction. Only five distinct populations remain, and the Gunnison Basin has the highest population diversity. Efforts to introduce sage grouse to New Mexico, Oregon, Montana, Wyoming, Utah, Colorado, and Idaho have been unsuccessful.

Gunnison sage grouse have a potential distribution of 46,521 sq km, but a current range of 4,787 sq km. There is a large difference between the potential and actual distribution of populations, which may be due to habitat alteration and degradation.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Gunnison sage grouse are a sagebrush ( Artemisia ) obligate species and also depend on a variety of other grasses and habitats for mating, nesting, and brood-rearing. There are three categories of sage grouse populations: non-migratory, one stage migratory, and two stage migratory. Populations that are non-migratory display limited movement regardless of season. One stage migratory populations prefer different habitat conditions in summer and winter. Three stage migratory populations prefer different habitats for winter, summer, and mating seasons. Mating habitats are often low vegetative density areas with high visibility called leks. Regardless of migratory preferences, all sage grouse populations rely on sagebrush and riparian habitats for feeding and cover. They are found at elevations of 2,200 to 4,300 m.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland

• Other Habitat Features
• agricultural agricultural
• riparian riparian

Physical Description

Gunnison sage grouse display sexual dimorphism. Males have white breasts with two round yellow air sacs (cervical apteria) on their chest. These air sacs have scale-like feathers that males inflate (making a popping noise) during the spring to attract mates. Males have a black belly with a white V-shaped area separating their throat from their chest. They also have spiky brown and white tail feathers that can be fanned out for sexual signaling. Females are smaller and lighter than males and have a gray-brown coloration. Female have shorter tail feathers with less plumage and also lack the prominent air sacs present on males. Chicks resemble females and have a brown and white speckled appearance for camouflage. Adult sage grouse from southwestern Colorado have shorter and narrower beaks than adult sage grouse from northern Colorado. There are also morphological variations between Gunnison sage grouse and their close relative, greater sage grouse Centrocercus urophasianus . Gunnison sage grouse are smaller with longer black filoplumes on their heads. They are typically 32 to 51 cm long with a wingspan of 6 to 76 cm and a mass of 990 to 2435 g.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• male more colorful
• sexes shaped differently
• ornamentation ornamentation

Reproduction

Gunnison sage grouse display "clumped polygyny," where multiple males compete to mate with females on an arena called a lek. Beginning mid-March through late May, many males begin to migrate to lek sites and often return to the same one each season. Males are very territorial and may defend their lek from intruders. Only one or two males (10-15%) is rewarded with the chance to reproduce with the surveying females. Adult and yearling females often get the opportunity to breed, whereas only select adult males and rarely any yearling males are able to mate.

Leks are often in places with low vegetation and sagebrush cover to maximize visibility. Males compete for females by popping their air sacs and strutting back and forth around the lek for hours. A male can also fan out his tail to try and impress females. Male Gunnison sage grouse have slower courtship displays than their close relatives, greater sage grouse ( Centrocercus urophasianus ). There are structural differences in mating calls between the two species as well. Females in the Gunnison Basin and northern Colorado can distinguish between male courtship vocalizations. Due to regional differences, females often prefer courtship vocalizations from regions nearby. This preferential breeding behavior creates a reproductive barrier between populations of Gunnison sage grouse that are geographically separated and may be an underlying factor causing species isolation and endangerment. Research has also shown that mating outside of the lek occurs occasionally.

• Mating System
• polygynous polygynous

Males do not participate in either nesting or brood rearing processes. The pre-laying period is from late March to April, when hens search for the ideal nesting sites. Better nesting sites have a greater diversity of forbs and sagebrush for both nutrition and cover. Forbs are a good source of calcium, phosphorous, and proteins that hens feed on during the gestation period to lay healthy eggs. Nesting occurs from mid-April to June and hens may then migrate to locations far from the lek to find optimal nesting conditions. Hens select nest sites that have adequate sagebrush and grass to provide cover from predators while the hen is incubating the eggs. Hens are loyal to successful nesting areas and will return season after season.

Hens have one brood per season and lay 6 to 8 eggs that hatch in 25 to 27 days. Small clutch sizes and annual mating opportunities have resulted in decreasing population numbers. Despite the small clutch size, most eggs hatch in June. Chicks are precocial and weigh 30 g at birth on average. Soon after hatching, they leave the nesting area for a riparian habitat to feed on insects. Chicks are able to make short flights and feed on their own by 2 to 3 weeks of age. They may follow their mothers until the fall. Chicks are able to sustain flight by 5 to 6 weeks of age and are considered independent at 10 to 12 weeks of age. In the winter, chicks and mothers separate into sexually segregated flocks and may be reunited in the spring when flocks migrate to lek sites to compete for mates.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Besides reproduction, males take no part in nest building or brood rearing. Females look for nesting sites that have adequate coverage and resources to raise chicks. Herbaceous dicots are an important dietary requirement for egg laying and provide a rich source of protein and phosphorous. Females often return to the same nesting sites annually if nest success rates are high. Chicks follow the mothers shortly after hatching. Hens offer a limited amount of parental care and chicks are mostly on their own for food procurement.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
• pre-weaning/fledging
  • provisioning
    • female
• pre-independence
  • provisioning
    • female

Lifespan/Longevity

In the wild, Gunnison sage grouse have an expected lifespan of 3 to 6 years but can live up to 9 years. Survival rates are low in captivity, and their expected lifespan in captivity is 1 years. This makes rescue efforts difficult for this endangered species. The Colorado Division of Wildlife (CDOW) tried captive rearing and only 11 of 40 chick eggs survived their first year. Despite low survival rate in captivity, CDOW believe that better techniques for raising Gunnison sage grouse have been attained from the process. Sage grouse mortality is higher for males than for females in the wild due to their larger size and flashy appearance. Females and chicks have lower mortality rates because they have a speckled brown and white coloration that functions as camouflage.

Behavior

Sage grouse are social birds that travel in flocks and spend most of the day preening, stretching, and feeding. Each day begins with foraging, and then broods relax until twilight, when they begin looking for shelter and a place to roost. It has been estimated that sage grouse spend 60% of the day foraging. Sage grouse are considered sedentary, but are willing to travel long distances to find food and cover. In the winter, sage grouse have sexually segregated flocks and sometimes sage grouse will roost together in the sun for warmth. Flocks then reunite in the spring at leks where males strut and set up territories to try and mate with females. Often, older and more experienced males have better territories in the lek and attract more mates. In the summer, after most of the eggs hatch, hens and chicks forage together. Despite their heavy bodies, sage grouse are decent fliers and can fly up to 78 km/hr (50 mph). Flying is one of the best ways for them to respond to danger because Gunnison sage grouse have short legs which inhibit running.

• Key Behaviors
• terricolous
• flies
• diurnal diurnal
• motile motile
• sedentary sedentary
• social social

Home Range

Average migration distance and home range varies by season and sex, according to research in Utah from 2002 to 2004. From summer to winter, adult males and females traveled 4.6 km and 4.4 km, respectively, between 2002 and 2003. Home range that year for adult males and females was 2.4 sq km and 3.5 sq km, respectively. From summer to winter the next year, adult males and females traveled 2.9 km and 5.9 km, respectively. Home range that year for adult males and females was 2.8 sq km and 2.5 sq km, respectively. Distance traveled by sexes fluctuates from year to year to mimic resource abundance changes.

Communication and Perception

Species can communicate with callings, courtship vocalizations, and feather signaling. Callings can be used to defend territory or to alert others about a threat. Courtship vocalizations help females distinguish the fitness between males during mating season. On the lek, older males will establish and defend their territory by sometimes chasing or fighting other males. Males will often position themselves laterally to females to project the loudest sound. Feather signals are made by the spreading of the tail feathers or the flapping of the wings.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Gunnison sage grouse have varying food preferences, depending on the life stage and season. In the early summer, insects and forbs are an essential component of the chicks' diet. Insects provide a source of protein for growth and development. In late summer, chicks begin to forage on forbs, and sagebrush is later added to the diet. As sagebrush habitats dry out in colder months, adults and chicks forage on forbs and sagebrush in riparian habitats. In the fall and winter, most sage grouse consume mainly sagebrush leaves. Certain types of sagebrush can be preferred based on protein levels and leaf textures. Gunnison sage grouse do not have muscular gizzards, so it is difficult for them to grind and digest seeds.

• Primary Diet
• omnivore omnivore

• Animal Foods
• insects

• Plant Foods
• leaves
• seeds, grains, and nuts
• fruit

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Sage grouse are easy targets due to their large size and inability to run fast. Males are also ostentatious and can be spotted by predators relatively easily. Females and chicks have a lower mortality rate due to smaller mass and the ability to camouflage with their surroundings. There has been research showing that a decrease in black tailed jackrabbit ( Lepus californicus ) populations has led to an increase in predation of sage grouse. In other regions, decreases in preferred prey populations have resulted in a shift of preferred prey to sage grouse. Dense, tall vegetation can help provide cover to protect nests from predators. Coyotes ( Canis latrans ), ground squirrels ( Sciuridae ), and American badgers ( Taxidea taxus ) are common nest predators. Sage grouse are also a popular game bird. Colorado and Utah have prohibited hunting for sage grouse in certain areas to protect dwindling population numbers.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Light to moderate grazing in the early season can promote forb and arthropod abundance in both upland and riparian habitats, whereas intense foraging can cause detrimental decreases in sagebrush distribution and promote introduction of invasive grasses. Gunnison sage grouse are infected with some kinds of blood parasites ( Haemoproteus ).

• Ecosystem Impact
• keystone species keystone species

Economic Importance for Humans: Positive

Sage grouse and ranchers both depend on the same habitats. If ranching profits decrease, the pressure to sell land increases, which often results in habitat fragmentation. If sustainable yields can be attained from these lands, it can help protect the remaining sage grouse populations. Gunnison sage grouse have diverse seasonal habitat requirements which make them a potential keystone species for other grassland species.

• Positive Impacts
• ecotourism ecotourism
• research and education

Economic Importance for Humans: Negative

Gunnison sage grouse and ranchers depend on the same habitats, which may lead to competition of resources between livestock and sage grouse. However, this is a minor problem, as both ranchers and sage grouse seem to have a mutually beneficial relationship.

Conservation Status

Habitat fragmentation, invasive plant species, and low vegetative diversity are the main issues endangering Gunnison sage grouse populations. The Colorado Parks and Wildlife is working with the Colorado Cattlemen's Association, Gunnison County, and the Bureau of Land Management to better understand factors impacting Gunnison sage grouse populations. The Bureau of Land Management (BLM) has been working with the Candidate Conservation Agreement (CCA) to try and conserve public lands that have sage grouse populations. Locals have also shown an interest in protecting the remaining populations. In 2010, the US Fish and Wildlife Service (FWS) listed the sage grouse as "warranted but precluded" under the Endangered Species Act to indicate that, although the species is not of top priority, they play an important ecological role. By listing the sage grouse, it has helped raise awareness and protect sagebrush habitats from further fragmentation.

Other Comments

Gunnison sage grouse were not considered their own species until the 1990s because of close behavioral similarities to the greater sage grouse ( Centrocercus urophasianus ). However there are morphological, genetic, and mating pattern differences that distinguish the two species.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Priscilla Kuo (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Catherine Kent (editor), Special Projects.

References

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Falsetto, R., J. Soceka, J. Sowell, A. Stork. 2011. "Western State Colorado University" (On-line). Digital Land-Cover Map of the Gunnison Basin. Accessed November 14, 2012 at http://www.western.edu/academics/geology/research/landcover/digital-land-cover-map-of-the-gunnison-basin.html .

Gibson, R. 1996. Female choice in sage grouse: the roles of attraction and active comparison. Behavioral Ecology and Sociobiology , 39/1: 55-59. Accessed November 04, 2012 at http://www.springerlink.com/content/68wyw9qflmy27duh/ .

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Sohl, T. 2012. "Gunnison Sage-Grouse" (On-line). South Dakota Birds and Birding. Accessed October 29, 2012 at http://sdakotabirds.com/species/gunnison_sage_grouse_info.htm .

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Young, J., C. Braun, S. Oyler-McCance, J. Hupp, T. Quinn. 2012. A New Species of Sage Grouse from Southwestern Colorado. The Wilson Bulletin , 112 (4): 445-453. Accessed October 04, 2012 at http://newweb.western.edu/faculty/jyoung/files-documents/Young%20et%20al%202000.pdf .

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Fish and Wildlife Service. Determination for the Gunnison Sage-grouse as a Threatened or Endangered Species. FWS-R6-ES-2009-0080. MO: National Archives and Records Administration. 2010. Accessed November 14, 2012 at http://www.fws.gov/mountain-prairie/species/birds/gunnisonsagegrouse/75FR59804.pdf .

2012. "Encyclopedia of Life" (On-line). Centrocercus Minimus: Gunnison Sage Grouse. Accessed October 29, 2012 at http://eol.org/pages/900212/details .

2012. "Gunnison Reservoir" (On-line). Water Quality Utah. Accessed November 14, 2012 at http://www.waterquality.utah.gov/watersheds/lakes/GUNNISON.pdf .

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