Scholarly Work - Animal & Range Sciences
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/8931
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Item Evaluating the Cumulative Effects of Livestock Grazing on Wildlife With an Integrated Population Model(Frontiers Media SA, 2022-05) Milligan, Megan C.; McNew, Lance B.Livestock grazing can shape temperate grassland ecosystems, with both positive and negative effects on wildlife documented depending on a variety of grazing and site factors. Historically, research investigating the impacts of livestock grazing on wildlife has been limited by a narrow focus on simple “grazed” vs. “ungrazed” treatments or examining how grazing affects only a single vital rate in isolation. To overcome these limitations, we used a two-stage class, female-based integrated population model (IPM) to examine whether three grazing management regimes (season-long, rest-rotation, and summer rotation) differentially impacted population growth rates of sharp-tailed grouse (Tympanachus phasianellus) in eastern Montana and western North Dakota. We estimated 14 vital rates related to survival and fecundity and examined whether subtle cumulative effects of livestock grazing were present but not detected in prior analyses focused on single vital rates. While the management regimes did not differentially impact survival or fecundity of female grouse in our study system, we found evidence for significant cumulative impacts of grazing regime on population growth rates that were only apparent when all vital rates were evaluated concurrently. Population growth rates were higher in areas managed with season-long livestock grazing. The IPM framework encourages comprehensive investigations into the influence of covariates on critical components of species life histories and can assist in guiding management decisions in a world of limited resources. This integrated approach allowed us to more efficiently use multiple data types to provide a more complete picture of the effects of management on an important indicator species.Item Habitat Targets for Imperiled Grassland Birds in Northern Mixed-Grass Prairie(2020-07) Pulliam, John P.; Somershoe, Scott; Sather, Marisa; McNew, Lance B.Grassland bird populations are declining faster than any other avian guild in North America, and promotion of favorable habitat conditions in rangeland breeding cores is important for their maintenance. There is much information on associations between breeding grassland songbirds and vegetation attributes. However, previous results have been difficult to translate into management practices due to mismatch between the scale and metrics used in biological sampling and those used in management. Here, we evaluate the response of imperiled grassland bird species to vegetation conditions using metrics and scales accessible to managers. We focus on four species that are experiencing particularly 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, we evaluated the abundances of these species within their core distributions in northern Montana. We used temporally replicated point-counts and hierarchical models to estimate abundance and associations with plot-level (9-ha) vegetation conditions while accounting for spatially and temporally variable detectability. Exotic grass encroachment and shrub cover had negative or neutral effects on all species. Birds responded strongly to biomass at this scale, with chestnut-collared longspurs and Sprague's pipit preferring a range of 1 100 kg ha−1 to 1 400 kg ha−1, and McCown's longspurs selecting for the lowest available. Residual grass and litter cover were important for Baird's sparrows. Variable results among species emphasize the need for heterogeneity in vegetation structure and composition at scales larger than the plot. Our results provide guidance for managers interested in improving habitat for these species.Item Autonomous acoustic recorders reveal complex patterns in avian detection probability(2017-09) Thompson, Sarah J.; Handel, Colleen M.; McNew, Lance B.Avian point-count surveys are typically designed to occur during periods when birds are consistently active and singing, but seasonal and diurnal patterns of detection probability are often not well understood and may vary regionally or between years. We deployed autonomous acoustic recorders to assess how avian availability for detection (i.e., the probability that a bird signals its presence during a recording) varied during the breeding season with time of day, date, and weather-related variables at multiple subarctic tundra sites in Alaska, USA, 2013-2014. A single observer processed 2,692 10-minute recordings across 11 site-years. We used time-removal methods to assess availability and used generalized additive models to examine patterns of detectability (joint probability of presence, availability, and detection) for 16 common species. Despite lack of distinct dawn or dusk, most species displayed circadian vocalization patterns, with detection rates generally peaking between 0800 hours and 1200 hours but remaining high as late as 2000 hours for some species. Between 2200 hours and 0500 hours, most species\' detection rates dropped to near 0, signaling a distinctive rest period. Detectability dropped sharply for most species in early July. For all species considered, time-removal analysis indicated nearly 100% likelihood of detection during a 10-minute recording conducted in June, between 0500 hours and 2000 hours. This indicates that non-detections during appropriate survey times and dates were attributable to the species\' absence or that silent birds were unlikely to initiate singing during a 10-minute interval, whereas vocally active birds were singing very frequently. Systematic recordings revealed a gradient of species\' presence at each site, from ubiquitous to incidental. Although the total number of species detected at a site ranged from 16 to 27, we detected only 4 to 15 species on 5% of the site\'s recordings. Recordings provided an unusually detailed and consistent dataset that allowed us to identify, among other things, appropriate survey dates and times for species breeding at northern latitudes. Our results also indicated that more recordings of shorter duration (1-4min) may be most efficient for detecting passerines. Our paper describes in detail the vocalization patterns of subarctic birds based on analysis of >2,600 acoustic recordings. We found that most species were highly detectable immediately upon arrival on breeding areas and that detectability remained high for most hours of the day. Additionally, when processing audio recordings, we found that in any single 10-minute recording, the majority of species detected were noted within the first minute; thus, individuals that are present and available to be detected by song or call tend to be highly detectable during a discrete time interval and more frequent, shorter duration recordings might be a more efficient way to detect the species using a given sampling area.Item Fine-scale distribution modeling of avian malaria vectors in north-central Kansas.(2016-06) Ganser, Claudia; Gregory, Andrew J.; McNew, Lance B.; Hunt, Lyla A.; Sandercock, Brett K.; Wisely, Samantha M.Infectious diseases increasingly play a role in the decline of wildlife populations. Vector-borne diseases, in particular, have been implicated in mass mortality events and localized population declines are threatening some species with extinction. Transmission patterns for vector-borne diseases are influenced by the spatial distribution of vectors and are therefore not uniform across the landscape. Avian malaria is a globally distributed vector-borne disease that has been shown to affect endemic bird populations of North America. We evaluated shared habitat use between avian malaria vectors, mosquitoes in the genus Culex and a native grassland bird, the Greater Prairie-Chicken (Tympanuchus cupido), by (1) modeling the distribution of Culex spp. occurrence across the Smoky Hills of north-central Kansas using detection data and habitat variables, (2) assessing the occurrence of these vectors at nests of female Greater Prairie-Chickens, and (3) evaluating if shared habitat use between vectors and hosts is correlated with malarial infection status of the Greater Prairie-Chicken. Our results indicate that Culex occurrence increased at nest locations compared to other available but unoccupied grassland habitats; however the shared habitat use between vectors and hosts did not result in an increased prevalence of malarial parasites in Greater Prairie-Chickens that occupied habitats with high vector occurrence. We developed a predictive map to illustrate the associations between Culex occurrence and infection status with malarial parasites in an obligate grassland bird that may be used to guide management decisions to limit the spread of vector-borne diseases.Item Responses of male Greater Prairie-Chickens to wind energy development(2015-05) Winder, Virginia L.; Gregory, Andrew J.; McNew, Lance B.; Sandercock, Brett K.Renewable energy resources have received increased attention because of impacts of fossil fuels on global climate change. In Kansas, USA, optimal sites for wind energy development often overlap with preferred habitats of the Greater Prairie-Chicken (Tympanuchus cupido), a lek-mating prairie grouse of conservation concern. We tested for potential effects of energy development on male Greater Prairie-Chickens in north-central Kansas. We captured males at 23 leks located 0.04 to 28 km from wind turbines during a 2-yr preconstruction period (2007–2008) and a 3-yr postconstruction period (2009–2011). First, we tested for effects of proximity to turbines, habitat, and lek size on annual probability of lek persistence and changes in male numbers. We predicted that energy development might result in behavioral avoidance of areas close to turbines, resulting in increased rates of lek abandonment and fewer males attending surviving leks. We found that distance to turbine had a negative effect on lek persistence for leks <8 km from turbines during the postconstruction period, supporting the 8-km buffer zone recommended by the U.S. Fish and Wildlife Service as an offset for wind energy projects. Additionally, lek persistence was positively related to number of males counted at a lek and with grassland cover surrounding the lek. Second, we tested for effects of wind energy development on male body mass. We predicted that degraded habitat conditions might result in decreased body mass for males attending leks near turbines during the postconstruction period. Male body mass was ~2% lower during the postconstruction period, but distance to turbine did not affect body mass. Additional study is needed to determine whether short-term effects of turbines on lek persistence influence population viability of Greater Prairie-Chickens.