Theses and Dissertations at Montana State University (MSU)
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Item Carry-over effects in partially migratory greater sage-grouse, southwest Montana(Montana State University - Bozeman, College of Letters & Science, 2022) Waxe, James Andrew; Chairperson, Graduate Committee: Andrea Litt; This is a manuscript style paper that includes co-authored chapters.Migration is a common natural phenomenon and an important life history strategy for many animal species. Migration allows individuals to accommodate changing environmental conditions, with the potential to increase survival or future reproduction. Many migratory species are subject to carry-over effects, where conditions experienced during one season or life stage influence subsequent life stages. Previous research has largely focused on evaluating the influence of carry-over effects on long-distance migrants, but less is known about these influences on shorter-distance migrants. During research in southwest Montana and southeast Idaho, we used VHF radio collars, red blood cells, stable isotopes, and morphometric information to understand the influence of carry-over effects on Greater Sage-grouse. In this population, some individuals migrate only short distances, while others may not migrate at all. We evaluated the influence of 1) different migration strategies and breeding locations on the body condition of females before breeding and 2) how variation in pre-breeding body condition influenced subsequent reproduction. We found non-migratory individuals were in better pre- breeding body condition than migrants during years with less winter precipitation. Similarly, individuals who experienced less precipitation during the breeding season also had higher pre- breeding body condition. Pre-breeding body condition positively influenced offspring weight early in the breeding season, but this relationship was less apparent later in the season. Our data suggest carry-over effects occur in this population of sage-grouse, but the magnitude of these effects was largely dependent on environmental conditions and timing of breeding. With increasing evidence of carry-over effects in sage-grouse populations, managers should broaden their conservation strategies to account for all life stages. Protecting a variety of winter habitat both near and distant from breeding areas will ensure the persistence and reproductive contribution of individuals with different migration strategies. Furthermore, protecting all known sage-grouse leks provides variation within a single population which allows for flexibility to respond in changing environments. Maintaining or enhancing landscape-level habitat heterogeneity supports variable life-history strategies and is critical for sage-grouse conservation.Item An appraisal of endocrine activity in strutting sage grouse(Montana State University - Bozeman, College of Agriculture, 1969) Thorvilson, Roger CecilItem Survival and summer habitat selection of male greater sage-grouse (Centrocercus urophasianus) in southwestern Montana(Montana State University - Bozeman, College of Letters & Science, 2007) Wisinski, Colleen Lyn; Chairperson, Graduate Committee: Jay J. RotellaDuring the 20th century, Greater Sage-Grouse (Centrocercus urophasianus) populations in North America have declined by 69-99%. In southwest Montana little is known about the factors leading to declines in sage grouse populations; as a result, there are strong concerns regarding sage grouse population trends and habitat quality. I used radio-marked male sage grouse to obtain known-fate survival data and provide locations for habitat analyses. The objectives of the study were (1) to estimate survival rates of marked birds, and (2) to characterize the habitat used by sage grouse in southwestern Montana and compare it with available habitat. I used known-fate data to estimate annual survival, and I measured habitat attributes associated with aerial locations of instrumented sage grouse (use sites) and a series of randomly chosen locations within each study site (available sites).Item Breeding ecology, survival rates, and causes of mortality of hunted and nonhunted greater sage-grouse in central Montana(Montana State University - Bozeman, College of Letters & Science, 2006) Sika, Jenny Lyn; Chairperson, Graduate Committee: Jay J. RotellaDeclines in productivity have been implicated in population declines for greater sage-grouse (Centrocercus urophasianus) in several areas, but there is considerable variation in reproductive effort, reproductive success and female survival, both temporally and spatially, and more data are needed. Despite declining populations, sage grouse are still legally harvested in most of their current range, including Montana, and uncertainty about how harvest impacts sage grouse vital rates remains. The reproductive activity, survival rates, and causes of mortality of hunted and nonhunted sage grouse females were monitored year round using radio-telemetry in central Montana during 2004 and 2005. Data on nest survival and brood survival were also collected. Nest survival was greater for renests, 0.56, than for first nests, 0.32. Brood survival to 30 days posthatch was estimated as 0.79. Reproductive effort and reproductive success were higher in 2005. Female survival during the nesting season was constant, 0.94 monthly.