The largest and most numerous of North America's 3 species of ptarmigan, the Willow Ptarmigan is a characteristic feature of arctic, subarctic, and subalpine tundra. This species has developed a variety of behavioral and physiological adaptations for living in extreme northern environments, where temperatures and light levels vary dramatically and predators abound: feathered tarsi that function as snowshoes, use of snow burrows for shelter, and a complex pattern of molting that results in cryptic plumage year-round. Both the Willow Ptarmigan and its congener the Rock Ptarmigan (Lagopus muta), have Holarctic distributions; they are the only 2 grouse species with a circumpolar distribution.

Willow Ptarmigan are usually monogamous, but 5–9% of males may be polygynous. Unusual for grouse, pairs remain together from the beginning of the breeding season until their chicks are independent. This is the only grouse in which the male is regularly involved in parental care.

Field studies of the conspecific Red Grouse (Lagopus lagopus scoticus) in Great Britain and Willow Grouse (L. l. lagopus) in continental Europe conducted during the past century have yielded comprehensive information on the life history and behavior of the species, in addition to substantive contributions to wildlife population dynamics and life history theory ( Jenkins, D., A. Watson and G. R. Miller. 1963. Population studies on Red Grouse, Lagopus lagopus scoticus (Lath.) in north-east Scotland. J. Anim. Ecol. no. 32:317-376. Close Jenkins et al. 1963, Watson, A. and D. Jenkins. 1964. Notes on the behaviour of the Red Grouse. Br. Birds no. 57:137-170. Close Watson and Jenkins 1964, Cramp, S. and K. E. L. Simmons. 1980a. Handbook of the birds of Europe and the Middle East and north Africa: the birds of the western Palearctic, Vol. 2. Hawks to bustards. Oxford: Oxford Univ. Press. Close Cramp and Simmons 1980a, Pedersen, H. C., J. B. Steen and R. Andersen. 1983. Social organization and territorial behaviour in a Willow Ptarmigan population. Ornis Scand. no. 14:263-272. Close Pedersen et al. 1983). Unlike its wily European counterpart, the Willow Ptarmigan in most of North America (with the exception of Newfoundland) is relatively tame and may be observed and captured readily. Population dynamics studies began more than 30 yr ago in Newfoundland ( Peters, S. S. 1963b. Population dynamics of the Newfoundland Willow Ptarmigan on the Avalon Peninsula. Ph.D. thesis, Cornell Univ., Ithaca, NY. Close Peters 1963b, Mercer, W. E. 1967b. Ecology of an island population of Newfoundland Willow Ptarmigan. St John's: Newfoundland and Labrador Wildl. Serv. Close Mercer 1967b, Bergerud Bergerud, A. T. 1970a. Population dynamics of the Willow Ptarmigan Lagopus lagopus alleni L. in Newfoundland 1955-1965. Oikos no. 21:299-325. Close Bergerud 1970a, Bergerud, A. T. 1970b. Vulnerability of Willow Ptarmigan to hunting. J. Wildl. Manage. no. 34:282-285. Close Bergerud 1970b) and in Alaska (Weeden Weeden, R. B. 1965c. Grouse and ptarmigan in Alaska: their ecology and management. Alaska Dep. Fish Game. Close Weeden 1965c, Weeden, R. B. 1967. Seasonal and geographic variation in the foods of adult White-tailed Ptarmigan. Condor no. 69:303-309. Close Weeden 1967). Studies on bioenergetics, nutrition, and biogeographic variation were conducted in Alaska (West and Meng West, G. C. and M. S. Meng. 1966. Nutrition of Willow Ptarmigan in northern Alaska. Auk no. 83:603-615. Close West and Meng 1966, West, G. C. and M. S. Meng. 1968. Seasonal changes in body weight and fat and the relation of fatty acid composition to diet in the Willow Ptarmigan. Wilson Bull. no. 80:426-441. Close West and Meng 1968, Irving et al. Irving, L., G. C. West and L. J. Peyton. 1967a. Winter feeding program of Alaska Willow Ptarmigan shown by crop contents. Condor no. 69:69-77. Close Irving et al. 1967a, Irving, L., G. C. West, L. J. Peyton and S. Paneak. 1967b. Migration of Willow Ptarmigan in arctic Alaska. Arctic no. 20:77-85. Close Irving et al. 1967b, West West, G. C., S. Savage, L. Irving and L. J. Peyton. 1968c. Morphological homogeneity of a population of Alaska Willow Ptarmigan. Condor no. 70:340-347. Close West et al. 1968c, West, G. C. 1972. Seasonal differences in resting metabolic rate of Alaskan ptarmigan. Comp. Biochem. Physiol. no. 42A:867-876. Close West 1972). Since 1980, multiyear studies of behavior, mating systems, reproductive ecology, and fitness of individuals have been conducted in northwestern British Columbia (Hannon Hannon, S. J. 1983. Spacing and breeding density of Willow Ptarmigan in response to an experimental alteration of sex ratio. J. Anim. Ecol. no. 52:807-820. Close Hannon 1983, Hannon, S. J. and J. N. M. Smith. 1984. Factors influencing age-related reproductive success in the Willow Ptarmigan. Auk no. 101:848-854. Close Hannon and Smith 1984, Martin, K. and S. J. Hannon. 1987. Natal philopatry and recruitment of Willow Ptarmigan in north central and northwestern Canada. Oecologia no. 71:518-524. Close Martin and Hannon 1987, Mossop, D. H. 1988. "Winter survival and spring breeding strategies of Willow Ptarmigan." In Adaptive strategies and population ecology of northern grouse., edited by A. T. Bergerud and M. W. Gratson, 330-378. Minneapolis: Univ. of Minnesota Press. Close Mossop 1988, Hannon and Martin Hannon, S. J. and K. Martin. 1992. Monogamy in Willow Ptarmigan: is male vigilance important for reproductive success and survival of females? Anim. Behav. no. 43:747-757. Close Hannon and Martin 1992, Hannon, S. J. and K. Martin. 1996. "Mate fidelity and divorce in ptarmigan: polygyny avoidance on the tundra." In Partnerships in birds: the study of monogamy., edited by J. M. Black, 192-210. Oxford: Oxford Univ. Press. Close Hannon and Martin 1996); near Hudson Bay, Manitoba (Martin Martin, K. 1984b. Reproductive defense priorities of male Willow Ptarmigan (Lagopus lagopus): enhancing mate survival or extending paternity options? Behav. Ecol. Sociobiol. no. 6:57-63. Close Martin 1984b, Martin, K. 1991a. Experimental evaluation of age, body size and experience in determining territory acquisition in Willow Ptarmigan. Can. J. Zool. no. 69:1834-1841. Close Martin 1991a, Martin, K. and F. Cooke. 1987. Bi-parental care in Willow Ptarmigan: a luxury? Anim. Behav. no. 35:369-379. Close Martin and Cooke 1987, Martin, K., S. J. Hannon and R. F. Rockwell. 1989. Clutch size variation and patterns of attrition in fecundity of Willow Ptarmigan. Ecology no. 70:1788-1799. Close Martin et al. 1989); and in Ontario ( Thomas, V. G. 1984b. Winter diet and intestinal proportions of Rock and Willow Ptarmigan and Sharp-tailed Grouse in Ontario. Can. J. Zool. no. 62:2258-2263. Close Thomas 1984b). Much remains to be learned, however, about migration patterns, scale of dispersal, and life history differences among subspecies.