Sage grouse movements and habitat selection in North Park, Colorado
Date
1982
Authors
Schoenberg, Thomas John, author
Ryder, Ronald A., advisor
Braun, Clait E., advisor
Hein, Dale A., committee member
Walter, Richard G., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Sage grouse (Centrocercus urophasianus) movements and habitat selection were studied in North Park, Colorado during April-August 1979 and February-August 1980. Sixteen male (12 adults, 4 juveniles) and 22 female (13 adults, 9 juveniles) sage grouse were captured and fitted with radio transmitters. Mortality of radio-marked sage grouse during the monitoring period was low (13%). Raptors were the most important predators. Twenty-two of 36 (61%) transmitters were recovered after use on sage grouse. Wildlife Materials transmitters had longer (P< 0.05) average life (209 days) than AVM transmitters (136 days). Sage grouse used 2 major wintering areas in the northeast and southeast quadrats of North Park in 1980. Preferred winter habitat encompassed only 3. 7% of the sagebrush (Artemisia spp.) – dominated land in North Park. There was no difference (P > 0.05) between sexes in average daily winter movements or size of winter range areas. Daily movements averaged 1.6 and 1.5 km for males and females, respectively. Winter flock break-up and dispersal to breeding areas began during the 2nd week of April coincident with the onset of the spring thaw. Movements of 3 radio-marked males from the wintering area to leks averaged 27.5 km. Four hens traveled an average of 29.9 km from the wintering area to nests. Daily movements of males from leks to feeding-loafing (FL) sites averaged 0.9 km. Dispersal direction from Raven Lek to FL sites was nonrandom (P < 0.001). Average distance that hens traveled from leks to nest sites was 2.7 km. Adult hens traveled farther (P < 0.05) than juvenile hens. Pre-incubation movements from nests to FL sites averaged 0. 4 km. Movements of both sexes from breeding areas and nests to meadows along the Michigan and Canadian rivers occurred throughout June, primarily during the latter half of the month. Four of 5 radio-marked males and 5 of 6 radio-marked hens moved to the meadow nearest the lek attended or nest site, respectively. Summer movements were restricted to relatively small areas along the Michigan and Canadian rivers. Few differences in slope and aspect were observed between habitats selected by sage grouse and random sites. Greater differences in habitat selection were seen when topographic features were examined. Sage grouse winter FL sites were primarily in sagebrush-dominated draws and on windswept ridges whereas breeding season FL sites were predominantly on 0-5 and 6-10% open slopes. Hens with broods preferred draws with little sagebrush and high forb and grass cover. Sage grouse selected winter FL habitats with better (P ≤ 0.05) structural cover (sagebrush clump size, plant dimensions, canopy cover) than breeding season FL sites. Structural characteristics of nest sites, however, were more similar to winter FL sites. Only leks had poorer (P < 0.05) structural cover than random sites. Except for FL sites of males during the breeding season, sage grouse chose sagebrush with higher (P < 0. 05) percent foliation (75-78 %) than found at random sites (65%). Males, hens with broods, and unsuccessful hens chose summer meadow habitats with similar (P > 0. 05) forb and grass cover and grass height. Males selected breeding season FL sites with higher (P < 0. 05) soil organic matter content than did hens or that found at random sites. The higher organic matter content was attributed to 2, 4-D spraying of the area around Raven Lek in 1963 and subsequent decomposition of sagebrush plants. Discriminant function and principal components analyses were also used to investigate sage grouse habitat selection. Three discriminant functions explained 93. 6% of the total sample variance whereas 5 principal components explained 94. 1% of the sample variance. In both analyses, sagebrush plant size was the most important habitat factor separating different types of sage grouse use and random sites. Degree of microhabitat selection was the 2nd most important factor followed by sagebrush clump size and canopy cover. These analyses revealed differences in habitats selected by sage grouse between and within seasons as well as habitat differences between random and sage grouse use sites.
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Subject
Sage grouse -- Habitat -- Colorado
Game and game-birds -- Habitat -- Colorado
Bird populations -- Colorado -- North Park
Habitat selection -- Colorado -- North Park
Sage grouse -- Colorado -- North Park