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Grouse are a group of birds from the
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
Galliformes Galliformes is an order of heavy-bodied ground-feeding birds that includes turkeys, chickens, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems as seed dispersers and predators, and are ofte ...
, in the
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Phasianidae The Phasianidae are a family of heavy, ground-living birds, which includes pheasants, partridges, junglefowl, chickens, turkeys, Old World quail, and peafowl. The family includes many of the most popular gamebirds. The family is a large one ...
. Grouse are presently assigned to the
tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confl ...
Tetraonini (formerly the subfamily Tetraoninae and the family Tetraonidae), a classification supported by
mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
sequence studies, and applied by the
American Ornithologists' Union The American Ornithological Society (AOS) is an ornithological organization based in the United States. The society was formed in October 2016 by the merger of the American Ornithologists' Union (AOU) and the Cooper Ornithological Society. Its ...
, ITIS, International Ornithological Congress, and others. Grouse inhabit
temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...
and
subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Genera ...
regions of the
Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
, from pine forests to
moorland Moorland or moor is a type of habitat found in upland areas in temperate grasslands, savannas, and shrublands and montane grasslands and shrublands biomes, characterised by low-growing vegetation on acidic soils. Moorland, nowadays, generall ...
and
mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher ...
side, from 83°N (
rock ptarmigan The rock ptarmigan (''Lagopus muta'') is a medium-sized game bird in the grouse family. It is known simply as the ptarmigan in the UK. It is the official bird for the Canadian territory of Nunavut, where it is known as the ''aqiggiq'' (ᐊ� ...
in northern
Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland ...
) to 28°N ( Attwater's prairie chicken in
Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
). Turkeys are closely related to grouse and are also classified in the tribe Tetraonini. The koklass pheasant is also closely allied with them.


Description

Grouse are heavily built like other Galliformes, such as
chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...
s. They range in length from , and in weight from . Males are larger than females—twice as heavy in the
western capercaillie The western capercaillie (''Tetrao urogallus''), also known as the Eurasian capercaillie, wood grouse, heather cock, cock-of-the-woods, or simply capercaillie , is a heavy member of the grouse family and the largest of all extant grouse species. ...
, the largest member of the family. Grouse have feathered nostrils. Their legs are covered in feathers down to the toes, and in winter the toes, too, have feathers or small scales on the sides, an adaptation for walking on snow and burrowing into it for shelter. Unlike other Galliformes, they have no spurs.


Feeding and habits

These birds feed mainly on vegetation—buds,
catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect-pollinated (as in '' Salix''). They contain many, usually unisexual flowers, arrang ...
s, leaves, and twigs—which typically accounts for over 95% of adults' food by weight. Thus, their diets vary greatly with the seasons. Hatchlings eat mostly insects and other
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...
s, gradually reducing their proportion of animal food to adult levels. Several of the forest-living species are notable for eating large quantities of
conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ext ...
needles, which most other
vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
s refuse. To digest vegetable food, grouse have big
crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydroponi ...
and gizzards, eat grit to break up food, and have long
intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans an ...
s with well-developed caeca in which
symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or para ...
bacteria digest
cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wa ...
.
Forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
species flock only in autumn and winter, though individuals tolerate each other when they meet. Prairie species are more social, and
tundra In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mou ...
species (ptarmigans, ''
Lagopus ''Lagopus'' is a small genus of birds in the grouse subfamily commonly known as ptarmigans (). The genus contains three living species with numerous described subspecies, all living in tundra or cold upland areas. Taxonomy and etymology The ge ...
'') are the most social, forming flocks of up to 100 in winter. All grouse spend most of their time on the ground, though when alarmed, they may take off in a flurry and go into a long glide. Most species stay within their breeding range all year, but make short seasonal movements; many individuals of the ptarmigan (called rock ptarmigan in the US) and
willow grouse The willow ptarmigan () (''Lagopus lagopus'') is a bird in the grouse subfamily Tetraoninae of the pheasant family Phasianidae. It is also known as the willow grouse and in Ireland and Britain, where the subspecies '' L. l. scotica'' was previo ...
(called willow ptarmigan in the US) migrate hundreds of kilometers.


Reproduction

In all but one species (the
willow ptarmigan The willow ptarmigan () (''Lagopus lagopus'') is a bird in the grouse subfamily Tetraoninae of the pheasant family Phasianidae. It is also known as the willow grouse and in Ireland and Britain, where the subspecies '' L. l. scotica'' was prev ...
), males are
polygamous Crimes Polygamy (from Late Greek (') "state of marriage to many spouses") is the practice of marrying multiple spouses. When a man is married to more than one wife at the same time, sociologists call this polygyny. When a woman is marri ...
. Many species have elaborate courtship displays on the ground at dawn and dusk, which in some are given in leks. The displays feature males' brightly colored combs and in some species, brightly colored inflatable sacs on the sides of their necks. The males display their
plumage Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
, give vocalizations that vary widely between species, and may engage in other activities, such as drumming or fluttering their wings, rattling their tails, and making display flights. Occasionally, males fight. The nest is a shallow depression or scrape on the ground—often in cover—with a scanty lining of plant material. The female lays one
clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
, but may replace it if the eggs are lost. She begins to lay about a week after mating and lays one egg every day or two; the clutch comprises five to 12 eggs. The eggs have the shape of hen's eggs and are pale yellow, sparsely spotted with brown. On laying the second-last or last egg, the female starts 21 to 28 days of incubation. Chicks hatch in dense, yellow-brown down and leave the nest immediately. They soon develop feathers and can fly shortly before they are two weeks old. The female (and the male in the willow grouse) stays with them and protects them until their first autumn, when they reach their mature weights (except in the male
capercaillie ''Tetrao'' is a genus of birds in the grouse subfamily known as capercaillies. They are some of the largest living grouse. Taxonomy The genus ''Tetrao'' was introduced in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of hi ...
s). They are sexually mature the following spring, but often do not mate until later years.


Populations

Grouse make up a considerable part of the vertebrate
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...
in the Arctic and Subarctic. Their numbers may fall sharply in years of bad weather or high predator populations—significant grouse populations are a major food source for
lynx A lynx is a type of wild cat. Lynx may also refer to: Astronomy * Lynx (constellation) * Lynx (Chinese astronomy) * Lynx X-ray Observatory, a NASA-funded mission concept for a next-generation X-ray space observatory Places Canada * Lynx, ...
, foxes,
marten A marten is a weasel-like mammal in the genus ''Martes'' within the subfamily Guloninae, in the family Mustelidae. They have bushy tails and large paws with partially retractile claws. The fur varies from yellowish to dark brown, depending on ...
s, and birds of prey. However, because of their large clutches, they can recover quickly. The three tundra species have maintained their former numbers. The prairie and forest species have declined greatly because of habitat loss, though popular game birds such as the
red grouse The red grouse (''Lagopus lagopus scotica'') is a medium-sized bird of the grouse family which is found in heather moorland in Great Britain and Ireland. It is usually classified as a subspecies of the willow ptarmigan but is sometimes conside ...
and the ruffed grouse have benefited from habitat management. Most grouse species are listed by the
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
as "least concern" or "near threatened", but the greater and lesser prairie chicken are listed as "vulnerable" and the Gunnison grouse is listed as "endangered". Some subspecies, such as Attwater's prairie chicken and the Cantabrian capercaillie, and some national and regional populations are also in danger. The wild turkey suffered a precipitous decline in the past, but has since become abundant, even in developed areas.


Sexual size dimorphism


Male size selection

The phenotypic difference between males and females is called
sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
. Male grouse tend to be larger than female grouse, which seems to hold true across all the species of grouse, with some difference within each species in terms of how drastic the size difference is. The hypothesis with the most supporting evidence for the evolution of sexual dimorphism in grouse is sexual selection. Sexual selection favors large males; stronger selection for larger size in males leads to greater size dimorphism. Female size will increase correspondingly as male size increases, and this is due to heredity (but not to the extent of the male size). This is because females that are smaller will still be able to reproduce without a substantial disadvantage, but this is not the case with males. The largest among the male grouse (commonly dubbed 'Biggrouse') attract the greatest numbers of females during their mating seasons.


Mating behavior selection

Male grouse display
lekking A lek is an aggregation of male animals gathered to engage in competitive displays and courtship rituals, known as lekking, to entice visiting females which are surveying prospective partners with which to mate. A lek can also indicate an avail ...
behavior, which is when many males come together in one area and put on displays to attract females. Females selectively choose among the males present for traits they find more appealing. Male grouse exhibit two types: typical lekking and exploded lekking. In typical lekking, males display in small areas defending a limited territory, and in exploded lekking, displaying males are covered over an expansive land area and share larger territories. Male grouse can also compete with one another for access to female grouse through territoriality, in which a male defends a territory which has resources that females need, like food and nest sites. These differences in male behavior in mating systems account for the evolution of body size in grouse. Males of territorial species were smaller than those of exploded lekking species, and males of typical lekking species were the largest overall. The male birds that exhibit lekking behavior, and have to compete with other males for females to choose them, have greater sexual dimorphism in size. This suggests the hypothesis of sexual selection affecting male body size and also gives an explanation for why some species of grouse have a more drastic difference between male and female body size than others.


Contrast with other bird species

Sexual size dimorphism can manifest itself differently between grouse and other birds. In some cases, the female is dominant over the male in breeding behavior, which can result in females that are larger than the males.


In culture

Grouse are
game A game is a structured form of play, usually undertaken for entertainment or fun, and sometimes used as an educational tool. Many games are also considered to be work (such as professional players of spectator sports or games) or art (suc ...
, and hunters kill millions each year for food, sport, and other uses. In the United Kingdom, this takes the form of driven grouse shooting. The male
black grouse The black grouse (''Lyrurus tetrix''), also known as northern black grouse, Eurasian black grouse, blackgame or blackcock, is a large game bird in the grouse family. It is a sedentary species, spanning across the Palearctic in moorland and step ...
's tail feathers are a traditional ornament for hats in areas such as
Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to ...
and the
Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Sw ...
. Folk dances from the Alps to the North American prairies imitate the displays of lekking males.


Species


Extant genera


Extinct genera

* Genus ''
Proagriocharis ''Proagriocharis'' is a genus of extinct turkey relatives from the upper Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58
'' † ** '' Proagriocharis kimballensis'' † * Genus ''
Rhegminornis ''Rhegminornis calobates'' is an extinct species of turkey from the early Miocene of Florida. It was described by Alexander Wetmore Frank Alexander Wetmore (June 18, 1886 – December 7, 1978) was an American ornithologist and avian paleontolo ...
'' † ** '' Rhegminornis calobates'' †


References


Footnotes


General

* *


External links


Grouse videos
on the Internet Bird Collection * * {{Authority control * Bird common names Taxa named by William Elford Leach