Willow ptarmigan inhabit primarily subalpine and subarctic zones. During the summer, they can be found in areas where lush vegetation and a moist environment are present, including arctic valleys, treeline areas, marshy tundra and coastal regions. In Alaska and northern Canada, they are commonly found in areas containing patches of dense vegetation, especially those in which willow (Salix species) or birch (Betula species) shrubs are present. As cooler weather approaches, willow ptarmigan seek more protected areas. This often involves moving further into valleys or more densely vegetated areas within their breeding zone. It has also been observed that during the winter, females and juveniles tend to move into boreal forests in some areas, while the males remain in a subalpine habitat.
Red grouse, Lagopus lagopus scotica, is a subspecies that inhabits Scotland and Ireland. Scottish and Irish populations of red grouse inhabit areas in which heather is readily available. This plant is not only required for shelter and nesting, but also provides a valuable source of food to the population, as it is rich in phosphorus and nitrogen. Although the general area they inhabit is referred to as 'heather moorland', this category can be further broken down into five groups based on specific characteristics of the heather present in that area: dry heath, wet heath, degraded heather, blanket bog and rough moorland grazing. Scottish and Irish red grouse populations generally inhabit areas 150 m above sea level; however, populations have been found to live around sea level and inhabit lowland blanket bogs in northwest Ireland. (Aniskowicz, 1994; Johnsgard, 2008)
Willow ptarmigan have chunky bodies, ranging from 28 to 43 cm long, and weighing and average of 0.57 kg. They have short legs with feathered toes, a feature that enables them to navigate through loose snow. They have short tails (with an average of 118 mm or more for males and 116 mm or less for females) and wings (when folded, an average of 190 mm or more for males and 190 mm or less for females).
Willow ptarmigan molt seasonally. Their winter plumage is usually complete by November, depending on the geographic region of the population. It consists of white feathers covering the entire body except the tail, which remains black. However, the tail is often covered by other feathers on the body, making the bird appear completely white. When the spring arrives, the females’ plumage becomes a mottled brown and ochre, while the males have a rusty hazel or chestnut coloring with darker brown barring on the entire body except for the wings and tail. They also have red “combs” on their eyes which are generally more visible during the warmer months. During the fall, the plumage of both male and female willow ptarmigan becomes lighter, with the females’ plumage becoming more gray and white. The males keep the dark barring pattern but take on more ochre tones.
Red grouse populations of Scotland and Ireland do not develop the same white winter plumage as willow ptarmigan populations living in more northerly areas of Europe and North America (which are covered by snow for much of the year). Instead, they retain a plumage that is predominantly dark reddish-brown. This is likely due to the fact that populations in Ireland and Scotland are exposed to a milder maritime climate than populations living inland and further north. Some studies have also found that there is a possible trade off between white winter camouflage and the thermal benefits of keeping a darker plumage for better heat absorption. However, it has also been found that white plumage has physical characteristics that allow for slightly better insulation. For this reason, more studies must be done to determine whether or not white plumage is thermally disadvantageous. ("Ptarmigans", 1974; Johnsgard, 2008; Lethbridge College Virtual Wildlife, 2009)
Territorial establishment of the male willow ptarmigan occurs during early spring, with the males arriving about 2 weeks before the females. During the period of territorial establishment, males become intolerant of other males establishing territory. Breeding territories are usually smaller when the population is larger. Polygynous males also have larger territories than monogamous males.
There have been many different documented courtship displays by willow ptarmigan. Some of these include Tail-Fanning, Waltzing, Rapid-Stamping, Bowing and Head-Wagging. Most of these behaviors are displayed by the males of the species. When Tail-Fanning occurs, the male cocks his tail, sometimes fanning it, and lowers his wings to scrape the ground as he approaches a female. This behavior may lead into Waltzing, in which the male drapes his wings around the female and slowly circles her using short, high steps. He may also tilt his tail and angle his body towards her. Rapid-Stamping occurs when the male runs toward the female while slightly fanning his tail, arching his neck and holding his head low with the beak open. Bowing is a display in which the male raises and lowers his head while holding his body low to the ground. Head-Wagging can be performed by males or females. One member of the mating pair will crouch by its mate, while wagging its extended head side to side. This display is usually performed alternately. Females may also show submissive behavior, after which mating usually occurs.
Male willow ptarmigan develop nuptial plumage during April or May. This is a key visual signal for female attraction. The nuptial plumage is predominantly bright brown and white, and the supraorbital comb also becomes more prominent. Females are generally more attracted to males with larger territories, combs and more vigorous courtship displays. However, females may leave the territory if the display is too aggressive. Mating usually occurs after the female displays a submissive posture.
Male willow ptarmigan are usually monogamous within a season. Approximately 83 to 86% of pairs will remate the following year if both members of the mating pair survive. However, 5 to 20% of male willow ptarmigan are polygynous (mating with more than one female), and usually have larger territories than unpaired or monogamous males. Few female willow ptarmigan are polygynous. This is possibly due to the higher predation on nests of polygynous females. Monogamous females are accompanied by their mate for around 94% of their active diurnal period, which contributes to the slightly higher survival rate of monogamous females’ broods over broods of polygynous females. It has been suggested that most willow ptarmigan are generally not polygynous because hens are capable of preventing other females from settling with their mate. (Aniskowicz, 1994; Hannon and Martin, 1998; Hannon, 1984; Hannon, 1995; Johnsgard, 2008; Lethbridge College Virtual Wildlife, 2009)
Willow ptarmigans mate seasonally during the spring and summer. After mating, the ptarmigan pair excavates a bowl-shaped nest in the ground. These bowl nests are often sheltered from most sides, but one side of the nest is usually left unprotected as a means of escape. They are usually lined with leaves, grass and feathers, and range from 15 to 20 cm wide and 8 to 16 cm deep. Willow ptarmigan generally lay between 4 and 14 eggs which are usually incubated for 20 to 23 days in late June to early July. When a developed chick is ready to hatch and makes the first cracks on it's eggshell (also known as 'pipping'), eggs usually hatch within a few hours. Hatching occurs during daylight hours. Willow ptarmigan hatchlings are precocial and usually weight about 15 g. They grow extremely fast and leave the nest to feed the same day they hatch. They no longer rely on their parents for warmth after 7 to 10 days, and are able to fly within 10 to 12 days. Chicks are usually adult-sized by autumn and are able to fend for themselves by this time (about 5 to 7 months of age). Both male and female willow ptarmigan are capable of breeding as yearlings however, not all yearling males will acquire territory or a mate. (Aniskowicz, 1994; Hannon and Martin, 1998; Johnsgard, 2008; Lethbridge College Virtual Wildlife, 2009)
Willow ptarmigan are the only members of the grouse family in which males exhibit significant parental care. A male willow ptarmigan stays by the nest to defend his clutch and female during the incubation period, and will defend the brood until the chicks are independent (around autumn). Females usually brood the chicks however, lone males are capable of successfully raising chicks. It has also been observed that parents and replacement males may adopt unrelated chicks. A study in which male mates were removed from the territory after incubation had begun showed that 50% of the previously unpaired males and 5% of the paired males joined the widows to give care to and defend the chicks. Observations show that replacement males are generally younger, more vocal and sit closer to the nest than parental males. Possible motivations for unpaired males to adopt unrelated chicks include the possibility of mating with the female should the first brood be unsuccessful and gaining mating experience in order to attract a mate in subsequent breeding seasons. (Aniskowicz, 1994; Hannon and Martin, 1998; Martin, 1989)
Willow ptarmigan have an extremely high population turnover, with an annual mortality rate of 60% to 72%. This high mortality rate means there is significantly less competition for territory during breeding seasons than in other species. The primary cause of death in willow ptarmigan populations is predation, whereas death due to weather conditions or food shortage is rarely observed. However, it has been observed that in Scottish willow ptarmigan (red grouse) populations, hens’ access to sprouting vegetation noticeably influences the viability of chicks. Chick weight and egg size also play a role in the survival of Scottish willow ptarmigan chicks both in captivity and in the wild. The longest survival record of a male specimen is 9 years, and the longest survival recorded for a female is 8 years (both recorded in British Colombia). These survival records are based on banded birds returning to breeding areas.
Willow ptarmigan, like many Arctic species, undergo cyclical population fluctuations, with peaks every 9 to 10 years. It is thought that weather conditions and therefore the availability and quality of food may contribute to these fluctuations. (Campbell, et al., 1997; Hannon and Martin, 1998; Steen, et al., 1988)
Male and female willow ptarmigan behavior patterns are generally quite similar. Willow ptarmigan are nomadic during the winter, and move depending on where they are able to find necessary food and shelter. This period of movement generally occurs between November and March. During this time, willow ptarmigan are quite social and generally feed and roost close together, possibly to conserve body heat. Resting is usually done in a standing or crouching position with the neck pulled back and the head close to the body. In order to save energy, willow ptarmigan will often build snow burrows and roost in them during colder weather.
Willow ptarmigan have many types of aggressive behavior. Two common displays are jumping and facing. Jumping occurs when two or more birds of either sex jump around and flap their wings. Chasing may also occur if a dominant male overpowers a more submissive bird. Chasing can last over great distances, and often ends with the more dominant bird injuring or even killing the submissive bird. Facing occurs when two equally dominant birds face each other with combs erect and heads forward. Both birds flick their wings, and neither shows signs of submission or retreat. Intersexual competition is quite rare, but it may occur during early courtship. Females show less conspicuous displays of aggression than males. It has also been observed that polygynous females spend more time fighting than monogamous females.
Willow ptarmigan move by either walking or running. They may also creep slowly when crossing snowfields or if they sense a predator is nearby. They rarely swim or dive, and do not often fly unless trying to escape from a predator or survey an area.
Willow ptarmigan usually bathe in dust, sand, dry dirt or snow by fluffing their feathers up and using their wings to flip sand, dirt or snow onto their backs.
Frolicking is a form of play that occurs in willow ptarmigan family groups, or sometimes entire flocks. The birds crouch low to the ground and jump around erratically while flapping their wings. (Andreev, 1991; Hannon and Martin, 1998; Johnsgard, 2008; Nash, 2005)
The size of a willow ptarmigan’s territory varies between breeding and winter seasons and also depends on availability of food and shelter. For this reason, it is difficult to obtain any reliable information for their population density and territory size. In Canada, estimates of population density range from 1 adult per square mile to as many as 8 adults per square mile. A study of Scandinavian willow ptarmigan populations determined territory sizes ranging from 6.7 to 7.9 hectares per male during the breeding season. Once pairs have been established, hens do not leave their partner’s territory for the duration of the breeding season. (Johnsgard, 2008; Steen, et al., 1992)
Several different communication sounds have been observed in willow ptarmigan and at least 11 different calls have been observed. Both sexes have territorial calls that are similar. However, ‘flight-song’, ‘rattle’, ‘kohwa’ and ‘aroo’ are only heard in males. ‘Koks’, ‘ko-ko-ko’ and ‘krrow’ sounds are heard in both males and females during threat, mating or territorial situations. These sounds may also be used to stay in contact with a mate or offspring. Females will ‘purr’ or ‘moan’ to communicate with their chicks. Both sexes will ‘hiss’ or ‘moan’ in defense of their offspring or mates. Males give calls that are noticeably stronger and more modulated than females' calls. Like all birds, willow ptarmigan perceive their environments through auditory, visual, tactile and chemical stimuli. (Hannon, 1995)
Willow ptarmigan generally maintain diets that contains 13 to 18% protein, 10 to 20% fiber, 5 to 10% lipids and up to 50% carbohydrates. However, during the winter their diets consist of less protein, but is much more abundant in fiber and carbohydrates. During the summer months, willow ptarmigan consume a variety of different foods, including willow (Salix species) buds, grass shoots, flowers, seeds, berries (including Vaccinium angustifolium, Vaccinium oxycoccos, Vaccinium vitis-idaea and Empetrum nigrum), insects, caterpillars and beetles. As winter approaches and the availability of insects and caterpillars decreases, the amount of berries, seeds and buds consumed increases. During the winter, food is often more difficult to find and willow ptarmigan must dig through the snow to find sustenance. Their winter diet is composed mainly of willow buds and twigs, as well as some birch (Betula species). Up to 94% of the winter diet may come from willow, with up to 80% being from a single Salix species. The adaptation of digestive enzymes and intestinal microflora to provide nutrition and energy from a single food source is unusual; however, studies suggest that willow ptarmigan are well adapted for obtaining nutrition and energy from a variety of different diets, and that although willow is a primary food source, the species is capable of deriving their nutrition from other sources.
Contrary to North American willow ptarmigan populations, Scotland's red grouse population (a subspecies of willow ptarmigan) has a diet consisting of mainly heather. This accounts for 95% of their diet during fall and midwinter months, falling to 90% with the approach of spring. During this time, the increased availability of Erica tetralix and Erica cinerea make up the remaining 10% of the diet. It has also been found that during nesting season, red grouse tend to select for heather rich in nitrogen and phosphorus.
There are typically two peak feeding times for willow ptarmigan during the winter months. During the morning, feeding occurs for approximately 2 hours, with the same time period being followed for evening feeding. It has been observed that as the daylight hours increase, feeding time also increases.
Willow ptarmigan chicks consume mainly caterpillars, insects, flowers and seeds, largely due to their need for a diet high in protein in order to facilitate extremely fast growth. Willow ptarmigan usually feed in flocks. The size of the flock generally increases or decreases depending on the availability and amount of food present. (Andreev, 1991; Aniskowicz, 1994; Bergerud and Mercer, 1972; West and Meng, 1966)
Willow ptarmigan have many known predators, many of which prey solely on eggs or willow ptarmigan chicks. It has been observed that predation on willow ptarmigan nests is much more common by avian predators than by mammalian predators.
In response to predators, willow ptarmigan will often freeze in a crouching position with their heads lowered and extended. They may perform a diversionary walk to distract predators from the nest or their mate, and may also feign injury by moving slowly along the ground while quivering their wings. This movement makes the ptarmigan appear as though it is dragging itself.
One of the most important anti-predator adaptations of willow ptarmigan is plumage that seasonally changes with the environment. As the snow melts and the surroundings change color, moulting from white to mottled brown occurs very quickly to ensure optimal camouflage. The same pattern is followed for each seasonal change, with the plumage rapidly changing to match the environment. It has also been observed that female willow ptarmigan will choose feeding areas in which they will be better camouflaged rather than ones that offer better nutritional benefits.
Several known predators of North American willow ptarmigan populations include: hooded crows, ravens, magpies, red foxes, pine martens, mink, short-tailed weasels, least weasels, gulls, northern harriers, golden eagles, bald eagles, rough-legged hawks, gyrfalcons, peregrine falcons, northern goshawks, snowy owls, wolverine, wolves, Arctic foxes, lynx and polar bears.
Known predators of Scottish red grouse populations include: red foxes, wildcats, golden eagles, hen-harriers, sparrow-hawks and common buzzards and rough-legged buzzards. Merlins and short-eared owls have been known to kill young red grouse (up to the age of about 8 weeks) however, they are not important predators for adult red grouse. (Hannon and Martin, 1998; Pedersen, et al., 2009; Steen, et al., 1992)
Willow ptarmigan are predators of various insect and beetle species. They may be infected with flukes (Trematoda species), tapeworms (Cestoda species), roundworms (Nematoda species) and ectoparasites. Many parasites are thought to decrease the body weight of willow ptarmigan, which can lead to death if the weight loss is severe enough. Although this has not been formally observed in North America, populations of red grouse in Scotland have experienced significant decline due to body parasites.
As well as being a predator to many invertebrates, willow ptarmigan are also prey to a number of larger bird and mammal species, including hooded crows, ravens, magpies, red foxes, gyrfalcons, wolverines, wolves and Arctic foxes. (Hannon and Martin, 1998; Holmstad, et al., 2005)
Willow ptarmigan are extremely popular upland game birds in North America and Europe and are regularly used for sport. A subspecies of willow ptarmigan, Scottish red grouse, have particularly important economic value in Scotland. The abundance of red grouse is often a determining factor in land value and revenue, and thus employment and use of the land. The decline of the Scottish red grouse population has lead to loss of revenue in the Central Highlands. (Barnes, 1987)
There are no known adverse effects of willow ptarmigan on humans. (Aniskowicz, 1994)
Willow ptarmigan are extremely widespread and their conservation status is of least concern. However, as of 2009, they were classified as critically imperiled in the province of Alberta, Canada. This does not follow the general trend for Canadian willow grouse populations, as populations in other provinces are classified as being either secure, apparently secure or unknown/under review.
Several new possible threats to ptarmigan populations have emerged in recent years. Although ecotourism has not directly altered ptarmigan populations, it has inadvertently contributed to the destruction of already fragile habitats that support this species. Pollutants are also becoming a more serious problem to many Arctic populations, including willow ptarmigan.
The Scottish red grouse population has shown significant decline in recent years. This is thought to have occurred primarily due to the reduction of heather abundance (which are a main food source for red grouse), caused by afforestation and farming. ("Lagopus lagopus", 2009; Lethbridge College Virtual Wildlife, 2009)
has several common names. These include: Alaska ptarmigan, Alexander ptarmigan, Allen ptarmigan, Arctic grouse, red grouse (found in Scotland), Scottish grouse, white grouse, white-shafted ptarmigan, willow grouse, willow partridge and willow ptarmigan.
There are several subspecies of willow ptarmigan in North America. Some of these include Lagopus lagopus albus, L. l. alascensis, L. l. alexandrae, L. l. ungavus, L. l. leucopterus, L. l. alleni, L. l. muriei, and Scottish red grouse (Lagopus l. scoticus). Most of these subspecies occupy their own geographical area. ("Red grouse (Lagopus lagopus)", 2010; "Scotland's Wildlife: Red Grouse", 2008; Aniskowicz, 1994; Johnsgard, 2008)
Sarah Morland (author), University of Alberta, Augustana Campus, Doris Audet (editor), University of Alberta, Augustana Campus, Rachelle Sterling (editor), Special Projects.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
A substance that provides both nutrients and energy to a living thing.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
having more than one female as a mate at one time
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
uses sight to communicate
young are relatively well-developed when born
2009. "Lagopus lagopus" (On-line). The IUCN Red List of Threatened Species. Accessed January 10, 2011 at http://www.iucnredlist.org/apps/redlist/details/141361/0.
Environment Canada Wildlife Service. Ptarmigans. CW 69-4/39. Ottawa: Information Canada. 1974.
2010. "Red grouse (Lagopus lagopus)" (On-line). ARKive. Accessed November 06, 2010 at http://www.arkive.org/red-grouse/lagopus-lagopus/#text=Biology.
2008. "Scotland's Wildlife: Red Grouse" (On-line). Scotland Outdoors. Accessed November 06, 2010 at http://www.bbc.co.uk/scotland/outdoors/articles/swrg/.
Andreev, A. 1991. Winter Adaptations in the Willow Ptarmigan. Arctic, 44/2: 106-114. Accessed September 28, 2010 at http://pubs.aina.ucalgary.ca.login.ezproxy.library.ualberta.ca/arctic/Arctic44-2-106.pdf.
Aniskowicz, B. 1994. "Bird Fact Sheets: Ptarmigan" (On-line). Hinterland Who's Who. Accessed September 21, 2010 at http://www.hww.ca/hww2.asp?id=64#sid7.
Barnes, R. 1987. Long-Term Declines of Red Grouse in Scotland. Journal of Applied Ecology, 24/3: 735-741. Accessed November 06, 2010 at http://www.jstor.org/stable/pdfplus/2403977.pdf.
Bergerud, A., W. Mercer. 1972. Spring Foods of Willow Ptarmigan Lagopus lagopus alleni in Southeastern Newfoundland. Oikos, 23/2: 213-217. Accessed November 05, 2010 at http://www.jstor.org/stable/pdfplus/3543408.pdf?acceptTC=true.
Campbell, R., N. Dawe, I. McTaggart-Cowan, J. Cooper, G. Kaiser, M. McNall. 1997. The Birds of British Columbia: Volume Two: Nonpasserines. British Columbia: University of British Columbia Press. Accessed October 12, 2010 at http://books.google.ca/books?id=U1TRsth_9j0C&pg=PA80&lpg=PA80&dq=willow+ptarmigan+territory+size&source=bl&ots=A3X5q5CX1K&sig=_hj9GvNxXJgU57sYmesp3om7vSE&hl=en&ei=rAq0TMvBN8KcnAfCpqznDA&sa=X&oi=book_result&ct=result&resnum=7&ved=0CDIQ6AEwBg#v=onepage&q=willow%20ptarmigan&f=false.
Hannon, S., K. Martin. 1998. "Willow Ptarmigan (Lagopus lagopus)" (On-line). The Birds of North America Online. Accessed September 18, 2010 at http://bna.birds.cornell.edu/bna/species/369/articles/introduction.
Hannon, S. 1984. Factors limiting polygyny in the willow ptarmigan. Animal Behaviour, 32/1: 153-161. Accessed November 05, 2010 at http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4K3KBJR-K&_user=1067472&_coverDate=02/29/1984&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1528975876&_rerunOrigin=google&_acct=C000051251&_version=1&_urlVersion=0&_userid=1067472&md5=b1ec6271c1ef79312508899b947ea113&searchtype=a.
Hannon, S. 1995. The calls and associated behavior of breeding willow ptarmigan in Canada. The Wilson Bulletin, 107/3: 496-509. Accessed September 28, 2010 at http://links.jstor.org.login.ezproxy.library.ualberta.ca/sici?origin=sfx%3Asfx&sici=0043-5643(1995)107%3A3%3C496%3ATCAABO%3E2.0.CO%3B2-X&.
Hannon, S., P. Eason. 1995. Colour bands, combs and coverable badges in willow ptarmigan. Animal Behaviour, 49/1: 53-62. Accessed September 28, 2010 at http://www.sciencedirect.com.login.ezproxy.library.ualberta.ca/science?_ob=MImg&_imagekey=B6W9W-4B7PWGF-6-3&_cdi=6693&_user=1067472&_pii=0003347295801537&_origin=search&_coverDate=01%2F31%2F1995&_sk=999509998&view=c&wchp=dGLbVlb-zSkzk&md5=be0b6781aacf6bfb8585a7f700d9c1b6&ie=/sdarticle.pdf.
Holmstad, P., P. Hudson, A. Skorping. 2005. The influence of a parasite community on the dynamics of a host population: a longitudinal study on willow ptarmigan and their parasites. OIKOS, 111/2: 377-391. Accessed October 11, 2010 at http://onlinelibrary.wiley.com/doi/10.1111/j.0030-1299.2005.13640.x/pdf.
Johnsgard, P. 2008. "Willow Ptarmigan" (On-line). University of Nebraska, Lincoln Nebraska. Accessed January 10, 2010 at http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1014&context=bioscigrouse.
Lethbridge College Virtual Wildlife, 2009. "Willow Ptarmigan" (On-line). Lethbridge College Virtual Wildlife Project. Accessed January 10, 2010 at http://www.lcvirtualwildlife.ca/index.php?option=com_content&view=category&layout=blog&id=89&Itemid=113.
Martin, K. 1989. Pairing and adoption of offspring by replacement male willow ptarmigan: behaviour, costs and consequences. Animal Behaviour, 37/4: 569-578. Accessed November 05, 2010 at http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4F1RW93-5M&_user=1067472&_coverDate=04/30/1989&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1529003309&_rerunOrigin=google&_acct=C000051251&_version=1&_urlVersion=0&_userid=1067472&md5=552cdf639b8f03779dc77d6b6fb70487&searchtype=a.
Mo Leng Wong, M. 2010. "Niche partitioning and spatial variation in abundance of Rock (Lagopus muta) and White-tailed Ptarmigan (L. leucura): a case of habitat selection at multiple scales" (On-line pdf). Accessed September 25, 2010 at http://repository.library.ualberta.ca/dspace/bitstream/10048/825/1/Wong_Mark_Spring+2010.pdf.
Nash, S. 2005. "Age and Sex Segregation of Wintering Willow Ptarmigan in Labrador" (On-line pdf). Accessed September 26, 2010 at http://www.bioone.org/doi/pdf/10.1656/1092-6194(2005)012[0113:AASSOW]2.0.CO;2.
Pedersen, A., N. Yoccoz, R. Ims. 2009. Prevalence of nest predators in a sub-Arctic ecosystem. European Journal of Wildlife Research, 56: 221-232. Accessed September 21, 2010 at http://www.springerlink.com.login.ezproxy.library.ualberta.ca/content/d8817706w6061j07/fulltext.pdf.
Steen, J., Ø. Andersen, A. Sæbø, H. Pedersen, K. Erikstad. 1988. Viability of Newly Hatched Chicks of Willow Ptarmigan Lagopus l. lagopus. Ornis Scandinavica, 19/2: 93-96. Accessed November 06, 2010 at http://www.jstor.org/stable/pdfplus/3676457.pdf.
Steen, J., K. Erikstad, K. Høidal. 1992. Cryptic Behaviour in Moulting Hen Willow Ptarmigan Lagopus l. lagopus during Snow Melt. Ornis Scandinavica, 23/1: 101-104. Accessed November 06, 2010 at http://www.jstor.org/stable/pdfplus/3676433.pdf?acceptTC=true.
West, G., M. Meng. 1966. Nutrition of Willow Ptarmigan in Northern Alaska. The Auk, 83/4: 603-615. Accessed November 06, 2010 at http://www.jstor.org/stable/pdfplus/4083152.pdf.