Populations generally occur at low densities, spaced by male and female territoriality during breeding, nesting, and, to a lesser extent, brood rearing (Keppie 1987). Females are territorial during breeding and nesting, and clearly avoid one another during this period (Herzog and Boag 1977, Robinson 1980). Males maintain their own territories during the courtship and nesting period, often using the same territory year-round for life (Robinson 1980). Only one male, in 5 years of study on two populations in Gogama, Ontario, was known to move its territory, and then only about 300 meters (Szuba and Bendell 1988). Female aggressive calls during mating and egg laying apparently resulted in evenly spaced female territories in Herzog and Boag's (1977) study in Alberta.
Rarely are "flocks" larger than 2 individuals in spring and summer (except for females with broods), and even in fall and winter, the average flock size calculated from observations of 268 flocks was 3.0 birds per flock (Ellison 1973). Larger autumn flocks (average of 3.8 birds) were partially accounted for by females still with broods. Telemetered birds showed that in late fall and winter flocks were very temporary, with the same birds associating for only a few days, and that birds were probably unrelated (Ellison 1973). The largest flocks recorded were 6 to 15 birds. Adult males apparently remain quite solitary even in winter, but juveniles are less solitary (Ellison 1973). Robinson (1980), in Michigan, found fall flocks of 4 to 12 spruce grouse, composed of mixed sexes, ages and families. The proportion of unbanded birds in these flocks was somewhat higher than that encountered in August, suggesting that birds were moving in from outside the study area, and that these larger flocks were probably composed of dispersing birds.
In Alaska, Ellison (1973) found that home range sizes were highly variable among individuals, ranging from 6 to 21 ha for preincubating females, 6 to 155 ha for brood-rearing females, 3 to 20 ha for molting males, 6 to 160 ha for either sex in fall, and 3 to 113 ha in winter. Robinson (1980) also reported highly variable range size for females with broods, but concluded that 12 to 16 ha would be adequate on the Yellow Dog Plains of Upper Michigan. Home range for broods on Mt. Desert Island, Maine, was 13-26 ha (O'Connell et al. 1995).
Two populations at Sevogle, New Brunswick, ranged from 9.8 to 21.9 grouse per sq km (adult males and females and yearlings present during period of 1 May to 30 June) over a 4 year period (Keppie 1987). Similar densities were reported for a population in southwestern Alberta, where population density in spring varied between 10.5 and 19.3 birds per sq km over a ten year period (Boag et al. 1979). Further data showed a fluctuation of between 5 and 30 birds per sq km over 21 years; a population decline was attributed to forest maturation (Boag and Schroeder 1987). It is interesting that population densities were so similar in these populations, because habitat characteristics were quite different. Populations in New York occur at estimated densities of 1.0 to 9.6 birds per sq km (composition unspecified, "breeding population;" Bouta and Chambers 1988). A Michigan population in the Yellow Dog Plains of Marquette County had 4.6 to 9.0 birds per sq km (presumably both sexes and yearlings) in spring (Robinson 1980). Grouse from Alaska's Kenai Peninsula occurred at intermediate spring densities of 7 to 11 birds per sq km (presumably both sexes and yearlings) over an area of habitat some 2000 sq km. This population must have numbered over 10,000 birds in the 1960s (Ellison 1973). The highest reported densities for this species are from central Ontario, where populations exceed 50 birds per sq km in prime habitat (Szuba and Bendell 1983). Keppie (pers. comm.) also has documented population densities of 50 birds per sq km. At Gogama, Ontario, Szuba and Bendell (1988) found densities of 28.0 to 36.0 males per sq km in May. One study in Alberta suggested that late spring population size was rather stable (Boag et al. 1979).
Young tend to disperse in the fall, but more so in some areas than others. Overall emigration rates for both sexes in New Brunswick exceeded emigration in an Alberta population (Keppie 1982). A higher percentage of female juveniles disperse than males (e.g., 95% vs. 77% in New Brunswick). Females were shown to disperse farther than males (an average of 5 km vs. 3.7 km, respectively) in a Michigan population (Robinson 1980).
In Alberta, yearling and adult annual survival averaged 68% overall (Boag et al. 1979). Female survival, at 63%, was lower than male survival, at 72%, producing a slight, but significant, male bias in sex ratio among adults (1.12 males: 1 females) (Boag et al. 1979). Annual survival rates for all adults and yearlings in New Brunswwick was 47% (Keppie 1987). Keppie (1979) reported an overwintering survival rate of 88% for all ages and sexes in a population in southwest Alberta. Overwinter survival of adults and yearlings, males and females was similar in this population. In Michigan's Yellow Dog Plains, adult males survived at rate of 50% per year, while females had a slightly lower rate of 45% per year. Robinson (1980) noted that the Michigan population's survival rate was intermediate between the Alberta populations and an Alaskan population described by Ellison, which had 31-38% adult survival. Robinson concluded that survival seems to balance clutch size variation throughout the range: the Alaskan population having the largest clutches, and lowest adult survival, Alberta at the opposite end with smaller clutches and highest survival, and Michigan in the middle on both traits.
There is little in the literature about longevity, despite many banding studies. The oldest individuals in Robinson's studies were three males, two that reached 6 years, and one that was at least 7.5 years old. The oldest female lived 5.5 years (Robinson 1980).
Although a number of studies of population dynamics have been conducted, it is still not possible to generalize about the main factors influencing population size across the species' range. Results in different populations and in different years within the same population have been contradictory. Rates of emigration and juvenile recruitment, especially survival through the first winter, clearly have a strong impact on population size, but these factors are not clearly related to density, or predictable from simple physical variables such as habitat characteristics or weather (Boag et al. 1979, Robinson 1980, Keppie 1982). Female and male territoriality may also affect some aspects of population density and production (Ellison 1973, Herzog and Boag 1977, Szuba and Bendell 1988).