Migration in a Local Population of Spruce Grouse

Abstract

-Migration of Spruce Grouse was observed in southwestern Alberta from 1970 to 1975 in a population of grouse that included both migratory and resident birds. Migrants comprised 39% of this population; these individuals migrated each year regardless of weather conditions. Migration occurred from mid-February to late May and from early September to midDecember. More females than males were migratory and females migrated longer distances. Distance between breeding and wintering sites ranged from 0.5 to 9.5 km. Survival and reproductive success was similar for migrant and resident grouse during the study. Migration was generally related to the dispersal history of birds as yearlings. Yearlings that dispersed in spring tended to establish migratory patterns by returning to winter sites used as juveniles. Why these birds did not remain on summer areas for the winter, as did resident Spruce Grouse, is uncertain. The quality of winter habitat may be an important factor in establishment of migration; further investigation is required to determine the qualitative aspects of the breeding and wintering habitat of Spruce Grouse. Migration has been reported for some species of the Tetraonidae, most notably Blue Grouse (Dendragapus obscurus; Anthony 1903, Marshall 1946, Wing 1947, Bendell 1955, Zwickel et al. 1968) and North American ptarmigan (Lagopus spp.; Weeden 1964, Irving et al. 1967, Hoffman and Braun 1975). Sage Grouse (Centrocercus urophasianus) undertake long seasonal movements but only in certain regions (Dalke et al. 1963, Eng and Schladweiler 1972, Wallestad 1975, Beck 1977). Sharptailed Grouse (Pedioecetes phasianellus) and Greater Prairie Chicken (Tympanuchus cupido) may travel long distances (Hamerstrom 1949, Hamerstrom and Hamerstrom 1951) although such movements occur only sporadically and have been difficult to document. Most reports suggest that changes in diet or food availability during winter may cause such movements, yet evidence is lacking. This paper is the first report of migration in Spruce Grouse (Canachites canadensis). Observations were made during studies of population size and movements of this species in southwestern Alberta (Keppie 1975, Herzog 1977). We report the proportion of a local population that was migratory, evaluate characteristics of seasonal travel, and investigate a possible relationship between the occurrence of migration and earlier dispersal of young birds. STUDY AREA AND METHODS Studies were conducted in the eastern foothills of the Rocky Mountains from May 1970 through September 1973 (Keppie 1979), April through October 1974, and February through December 1975 (Herzog and Boag 1978). The main study area encompassed 555 ha adjacent to Gorge Creek (50'39'N, 114'39'W), 27 km west of Turner Valley, Alberta. Forest cover was predominantly lodgepole pine (Pinus contorta) with scattered clumps of white spruce (Picea glauca) and poplar (Populus spp.). The study area was contiguous with habitat suitable for grouse except for a 1-km wide area along the east side. Grouse were censused regularly on the primary study area with the aid of pointing dogs. Birds were captured with extendable snare poles (Zwickel and Bendell 1967) and individually marked with colored leg bands. Essentially all birds (95%) were marked. Grouse were separated into three age-classes: juvenile (0-9 months of age; from hatching until 1 April), yearlings (9-21 months), and adults (greater than 21 months). Thus, yearlings were birds entering their first breeding season and were distinguishable from adults by tail feather patterns (Zwickel and Martinsen 1967) and shape of primaries until 14 months of age. Monthly we searched outside the main study area to obtain additional observations of migratory birds and distances they had travelled. Four migratory females were also radio-marked and monitored in 1975, using techniques described by Herzog (1979). Minimum daily movements were the distances between initial sightings on successive days. Contingency and goodness of fit chisquare tests, t-tests, G-tests and rank tests (Sokal and