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Item Associations of broad scale vegetation characteristics and abundances, nest densities, and nest survival of mixed-grass prairie songbirds in northern Montana(Montana State University - Bozeman, College of Agriculture, 2019) Pulliam, John Patrick; Chairperson, Graduate Committee: Lance McNewGrassland bird populations are declining faster than any other avian guild. In northern Montana, four species are experiencing severe population declines: Baird's sparrow (Centronyx bairdii), chestnut-collared longspur (Calcarius ornatus), McCown's longspur (Rynchophanes mccownii), and Sprague's pipit (Anthus spragueii). In 2017 and 2018, I evaluated abundance, nest density and nest survival of these species in relation to local vegetative conditions with the goal of identifying important breeding season vegetation conditions to inform management. I conducted fixed-radius point-counts at 100 sites to estimate local abundance, rope drag surveys to estimate nest density, nest monitoring to estimate nest survival, and vegetation surveys to estimate vegetation structure and composition across grassland habitats in Phillips County, MT. Point-counts and rope drag surveys were carried out with replicated visits to allow estimation of species-specific detection probabilities. Vegetation conditions were measured at the plot level (9-ha) to provide information at scales relevant for land managers. The abundance of Baird's sparrows was positively associated with residual grass cover and litter cover. Chestnut-collared longspur abundance was negatively associated with residual grass, exotic grass, and shrub cover and had a quadratic relationship with biomass. Plot-level abundance of McCown's longspurs was negatively associated with both shrub cover and biomass. Sprague's pipit abundance declined with exotic grass cover and exhibited a quadratic relationship with biomass. Limited sample size only allowed inference of nest density and nest survival for chestnut-collared longspurs. Nest density was negatively associated with plot scale exotic grass cover, biomass, and slope. I did not find support for any vegetation covariates on nest survival for chestnut-collared longspurs. These results provide some guidance for landscape managers interested in improving habitat for these species. The contrasting results among species, however, emphasize the need for heterogeneity in vegetation structure and composition. The disconnect between relevant covariates for nest density and nest survival suggest possible maladaptation for chestnut-collared longspurs. This result suggests that an index of productivity for this species that does not include both nest density and nest survival may produce erroneous results.Item Factors affecting nest survival of three species of migrant songbirds in the Greater Yellowstone Ecosystem(Montana State University - Bozeman, College of Letters & Science, 2006) Carle, Robin Jean; Chairperson, Graduate Committee: Jay RotellaIn the Greater Yellowstone Ecosystem (GYE), spatial patterns of habitat types and human land uses create an overlap between high-intensity human disturbance and productive habitat types at low elevations. This overlap suggests concern for species such as Neotropical Migrant songbirds, whose populations may depend on the productivity of individuals breeding in low-elevation habitats. We examined patterns of nest survival of three songbird species within the GYE to determine the relative importance of covariates of interest at nest-, patch-, and landscape-level spatial scales to nest survival. We hypothesized that covariates at several spatial scales would be important to nest survival and that broad-scale characteristics of the surrounding landscape would have the strongest spatial-level influence on nest survival. From 1997 to 1999 we located and monitored 233 nests of Dusky Flycatchers (Empidonax oberholserii), 129 nests of Warbling Vireos (Vireo gilvus), and 290 nests of Yellow Warblers (Dendroica petechia) in aspen and cottonwood habitats across southwestern Montana and adjoining portions of Idaho. We found that covariates at multiple spatial scales were important to the nest survival of all three species and that landscape-level variables had the strongest spatiallevel effects on the nest survival of Dusky Flycatchers and Yellow Warblers. For all three songbird species, higher substrates appeared to provide the most favorable nesting habitat and date and parasitism status were important variables in the model suites. Variation in the nest survival of Dusky Flycatchers was influenced by all spatial-level covariates, while the variation in nest survival of Yellow Warblers was influenced primarily by surrounding home density. Warbling Vireos appeared to be an edge species in the GYE, and their nest survival was influenced by smaller-scale covariates. Overall, our results emphasize variation in species' responses to surrounding habitat and land use features. We suggest that future studies should evaluate both a variety of species and a variety of habitat and land use features in order to determine how surrounding habitat and anthropogenic factors influence songbird communities.Item Effects of volcanic ash on the insect food of the Montserrat Oriole Icterus oberi Lawrence 1880(Montana State University - Bozeman, College of Agriculture, 2005) Marske, Katharine Ann; Chairperson, Graduate Committee: Michael A. Ivie.The Montserrat Oriole, Icterus oberi Lawrence, endemic to the West Indian island of Montserrat, has grown critically endangered since volcanic eruption began on that island in 1995. The Soufriere Hills Volcano has devastated much of the oriole's native habitat, and populations within intact forests have plummeted in recent years. One hypothesized cause for the Montserrat Oriole's decline is that low insect prey numbers during the nesting season, as a result of volcanic ash in the environment, is resulting in increased nest failure. The hypothesis of a negative effect of ash on canopy arthropods was tested. Four sites, varying in the level of ash deposition they typically receive, were sampled via canopy fogging over a 14-month period. Results indicate that ash is having a significant negative impact on canopy arthropods, particularly at the sampling sites closest to the volcano, but that the decline is limited to a few insect taxa.