<p>The success of medusahead (Taeniatherum caput-medusae ssp. asperum) as an invasive exotic grass in the western US is attributed in part to its low palatability. The nutritional context where medusahead grows can be modulated by the use of supplements that increase herbivores? preference for unpalatable feeds. Additionally, positive experiences early in life (with mother, with supplements) can have long-life influences on preference for unpalatable feeds. To test the influence of the nutritional context on medusahead intake, ewes grazed with their lambs during summer of 2013 on medusahead-infested rangeland with (Treatment) or without (Control) the daily provision of an energy-rich supplement. To test for the effect of experience early in life at grazing medusahead on use of this weed later in life, lambs that grazed with their mothers during 2013 (Experienced) were exposed to medusahead (in pens and during grazing) as yearlings during summer of 2014 along with inexperienced (Control) animals. To better understand the unpalatability of medusahead, the fermentation kinetics of medusahead at different phenological stages and particle sizes was assessed. Ewes grazing with their lambs showed low use of medusahead (5% of the grazing events recorded), even when supplemented. Nevertheless, medusahead use increased across the grazing period and utilization was similar to medusahead abundance in the plant community. Use of medusahead by nursing lambs was correlated with that observed by their mothers and lambs utilized medusahead to the same extent either before or after weaning. Yearlings in pens showed low intake of medusahead and a cyclic pattern of intake across days. However, experienced yearlings displayed a more even intake of medusahead across days and a greater gain-to-feed ratio than Control yearlings. All yearlings showed low to nil use of medusahead during grazing. Medusahead had lower fermentation rates than alfalfa hay and fermentation rates declined with plant maturity. Organic matter digestibility for medusahead declined as particle size of the substrate increased, a relationship that explains the low palatability of the weed. These results provide the foundation for grazing treatments aimed at reducing the abundance of the weed or at preventing its spread in rangelands with different levels of medusahead infestations.

Implementing conservation in the face of unprecedented landscape change requires an understanding of processes and scales that limit wildlife populations. We assessed landscape-level processes influencing sage-grouse (Centrocercus urophasianus), to a migratory population in the Milk River Basin (MRB), northeast Montana, USA, and south-central Saskatchewan, Canada. A regional analysis of leks (e.g., communal breeding sites) documented that populations impacted by the increasing extent of agricultural tillage, roads, and energy development out to spatial scales larger than previously known. Using bird abundance as a novel way to evaluate human impacts revealed relationships that would have been missed had we not incorporated lek size into analyses. For example, large leks are 4.5 times less likely to occur than small leks when agricultural tillage fragments 21% of land within 1.0km of breeding sites. Sage-grouse in the MRB met or exceeded demographic rates of stable or increasing populations, and thus, are not likely the cause for annual declines. Spring and summer survival of radio-marked females was higher in 2008 (0.91), than in 2007 (0.55), the year we documented an outbreak of West Nile virus. Nest sites in the MRB had lower shrub cover (15%) than range-wide estimates (15-56%), and overall shrub cover instead of sagebrush cover, was a better predictor of nest-site selection. Plains silver sagebrush (Artemesia cana cana) made up half of total shrub cover (7.1%) at nest sites, suggesting that other shrubs compensate for lower sagebrush densities in the MRB. We discovered the longest migratory event observed for sage-grouse, with females travelling 40km to120km from breeding to wintering areas in Wyoming big sagebrush (A. tridentata wyomingensis) habitats in Montana. Habitat may be sufficient to maintain a small population in the MRB, but its ability to persist through time and to buffer against stochasticity is depressed now that this once-large population has become small and isolated. For example, impacts of disease are compounded when acting on fewer individuals and working synergistically with fluctuations in growth rates. Consequently, conservation of sage-grouse in the MRB will depend on maintaining the current habitat base, and on restoring sagebrush-dominated grasslands currently occupied by agricultural tillage.

Environmental sources of mortality can exert strong selection pressures on growth strategies across taxa. Studies of growth responses need to consider multiple body components because components can compete for resources during growth in an integrated growth strategy. However, such studies are lacking and little is known about the extent to which body components may differ in their growth responses to environmental selection pressures. Theory predicts that growth of body components with relatively higher advantages for survival should be prioritized. For example, increases in time dependent mortality, like nest predation risk in birds, should favor growth of body features that enhance the ability to leave nests earlier. We studied 12 coexisting species of passerines to specifically test predictions that species with higher nest predation rates would prioritize growth of locomotor components (e.g. tarsi and wings) at the expense of growth of body mass. We also tested the prediction that these altricial birds should develop endothermy earlier to facilitate their ability to leave the warm nest environment. We found species that experience higher nest predation rates exhibited relatively faster growth rates of wing chord, but not tarsus, compared with body mass. Furthermore, species with higher nest predation rates achieved adult-sized tarsi and 60% of adult wing-chord lengths at relatively smaller body mass, further demonstrating the prioritization of wing and tarsus development. Species with higher nest predation risk also developed endothermy earlier at relatively smaller body mass. Thus, our results suggest that growth responses among species to differences in nest predation risk include an integrated strategy across body components to facilitate an ability to escape a risky environment.

<p>Biological control, using introduced, specialist insects is a common strategy for controlling plant invasions. However, the efficacy of biological control agents in controlling their host plants is rarely quantified population level. I quantified the impact of a specialist biological control agent, the cinnabar moth <i>(Tyria jacobaeae)</i> on its host plant, tansy ragwort <i>(Senecio jacobaea)</i> in northwest Montana. Cinnabar moth damage and its effects on important plant vital rates were tested with and without specialist herbivores. The presence of moth larvae corresponded to a reduction in population growth rates to less than one, compared to herbivore-free controls, indicating the potential for successful biological control by this insect. However, delayed effects of cinnabar moth herbivory on tansy ragwort vital rates were realized during the year following moth herbivory, after the moths had disappeared from the system. Individual damage to flowering plants in 2005 led to increased survival of these plants in the following year compared to controls, by reverting back to a vegetative state. In addition, seed set was reduced in plants that were damaged as juvenile rosettes in 2005 that went on to flower in 2006. When these delayed effects were combined in matrix models, gains in adult survival did not outweigh the decreases in fecundity or transition rates in terms of population growth and our initial conclusions remained unchanged. However, further study revealed that moth larvae were more likely to be depredated by carpenter ants in xeric sites suggesting that moth populations may not be sustained in these areas. Cinnabar moth larvae can be effective in this system provided they consume a large number of seeds (>90%) in consecutive years, but requires that moth populations are established and sustained from year to year. While herbivores do show the ability to control an invasive plant species, this relationship is strongly contextual in this system. This work emphasizes the importance of recognizing the influence of habitat context on the outcome plant-herbivore interactions, specifically in invaded ecosystems.</p>

<p>Effective conservation planning in the face of rapid land use change requires knowledge of which habitats are selected at landscape scales, where those habitats are located, and how species ultimately respond to anthropogenic disturbance. I assessed sage-grouse (Centrocercus urophasianus) large scale habitat ecology and response to energy development in the winter and nesting seasons using radio-marked individuals in the Powder River Basin, Montana and Wyoming, USA. Landscape scale percent sagebrush (Artemisia spp.) cover at 4-km2 was the strongest predictor of use by sage-grouse in winter. After controlling for vegetation and topography, the addition the density of coal-bed natural gas wells within 4 km2 improved model fit (AIC -6.66, wi = 0.965) and indicated that sage-grouse avoided energy development. Nesting analyses showed that landscape context must be considered in addition to local scale habitat features (wi = 0.96). Findings provide managers a hierarchical filter in which to manage breeding habitats. Twice the amount of nesting habitat at 3, 5 and 10-km scales surrounded active leks versus random locations. Spatially explicit nesting and wintering models predicted independent sage-grouse locations (validation R2 ≥ 0.98). I incorporated knowledge of energy impacts into a study design that tested for threshold responses at regional scales analyzing 1,344 leks in Wyoming from 1997-2007. Potential impacts were indiscernible at 1-12 wells within 32.2 km2 of a lek (~1 well / 640 ac). At higher wells densities a time-lag showed higher rates of lek inactivity and steeper declines in bird abundance 4 years after than immediately following development. I spatially prioritized core areas for breeding sage-grouse across Wyoming, Montana, Colorado, Utah and the Dakotas and assessed risk of future energy development. Findings showed that bird abundance varies by state, core areas contain a disproportionately large segment of the breeding population and that risk of development within core areas varies regionally. My analyses document behavioral and demographic responses to energy development, offer new insights into large scale ecology of greater sage-grouse and provide resource managers with practical tools to guide conservation.</p>

Understanding the relationship between a species important vital rates and how they respond to environmental factors is essential for developing appropriate conservation strategies. Historically, breeding populations of common loons existed across much of the northwestern United States, but that area of distribution within the lower 48 states has been significantly reduced. Montana still has the largest breeding population of common loons in the western continental United States, averaging 40-70 territorial pairs annually. Most research to date on loon population dynamics, habitat use, and response to disturbance was conducted in much larger populations of the Midwest and Northeast United States and did not account for individual vital rate importance. Recent sensitivity analysis showed that fecundity was the vital rate had the most influence on the population growth rate in common loons. Therefore, I designed my research to evaluate the relationships between disturbance (as measured by the number of houses, resorts, and campgrounds in relation to lake size), habitat, intraspecific interactions and territory occupancy and reproduction. I used occupancy models to explore the dynamics underlying occupancy of potential lakes. I observed that landscape scale effects were important to occupancy of loon territories. The abundance of feeding lakes and the number of territorial pairs within 10 km were equally important for explaining probabilities of occupancy. I suggest managers protect both occupied, as well as, unoccupied lakes, especially when in close proximity to clusters of territorial pairs and feeding lakes. I observed that lake scale effects were more important to reproductive potential than landscape scale effects. I found a significant negative relationship with islands and a significant positive relationship with shoreline complexity on reproduction. Shoreline disturbance did not appear important when compared to other factors, but there are factors associated with Montanas outreach and education program that probably affected this result. For increasing reproduction I suggest managers continue current management activities, but include a greater focus on protecting nesting habitat on lakes without islands. I also suggest managers continue to mitigate for disturbance while exploring other ways to evaluate the effects of disturbance on occupancy and reproduction.

Elk (Cervus elaphus) are increasing in fragmented landscapes that result from exurban human development throughout western North America. This problem is increasing human-wildlife conflicts and represents a significant new challenge to wildlife managers. Elk hunting must be intensively managed, if allowed at all, to reduce public relations problems. For example, the Montana Department of Fish, Wildlife & Parks has focused three hunts on a rapidly growing (~11% annually) elk herd in the wildland-urban interface (WUI) of Missoula, Montana, USA. Their goals were to reduce population growth rate, crop depredation, and habituation to humans. However, little was known about the indirect effect hunting has on anti-predator behavior, movement, resource selection, and human-elk conflicts. We first investigated the indirect effects of hunting on elk using an extensive comparison of elk anti-predator behavior across four human predation risk levels in western Montana. We collected 361behavioral observations across this predation risk gradient from October 2008 to March 2009. Vigilance was highest in highest predation risk areas and lowest in lowest risk areas. Vigilance and movement attenuated with the removal of human predation risk within 3-5 weeks under intermediate human predation risk in Missoula, Montana. I then used an intensive investigation of elk outfitted with global positioning system (GPS) collars in the WUI of Missoula to test the indirect effects of hunting on elk. We used data from nine GPS collared adult female elk during three hunting seasons with increasing hunting pressure (2007-2009) to test relationships between movement rates measured by first passage time (FPT) and resource selection. FPT decreased annually, by season type, and by hunting mode (archery vs rifle), and was negatively correlated with hunter predation risk. Elk slowed down ~750 meters from and selected for areas ~1200 meters from houses and trails, suggesting habituation to humans contributed to WUI human-wildlife conflict. These results support the risk allocation hypothesis that elk modify behavior in relation to temporal and spatial variation in human predation risk, and provide some of the first insights as to the indirect effects of hunting on elk in the WUI.

The smaller clutch size of tropical as opposed to north temperate birds has intrigued researchers for a long time. An untested hypothesis posits that higher nest predation in the tropics favors smaller nests thereby constraining clutch-size. We tested this hypothesis by conducting an experiment to test whether nest predation increases with nest size in a tropical forest. Furthermore, we studied north temperate and tropical birds to examine if: (1) predation rates increased with nest size, (2) nest sizes were smaller in the tropics, and (3) clutch size was explained by nest size controlled for body size. We used data on predation rates, nest sizes, and clutch sizes for > 2000 north temperate and tropical bird nests of 36 altricial bird species that nest in open cups. Nest predation risk increased with nest size in both the experiment and in the comparison across latitudes, justifying a major premise underlying the nest size hypothesis. However, nest sizes were not smaller in the tropics. As a result, clutch sizes were not related to nest sizes either between latitudes or within sites. Nest sizes were strongly correlated with adult body sizes. Hence, (1) body size might influence reproductive success by affecting nest predation through nest size; and (2) we rejected the hypothesis that nest size explains clutch size in the tropics.

Paternal care has been neglected in behavioral studies because it is rare among most animals. Birds express wide variation in male care across a broad life-history gradient, but such variation among species remains poorly explored. At the same time, contributions of male assistance with incubation have been largely overlooked with the assumption that incubation is a time of low parental energy expenditure. We compared male versus female biparental incubation effort between two tropical antbird species in the northern Andes of Venezuela. We found that males and females apportion reproductive effort differently between these two species, but that male contributions of time and incubation effort were generally greater than for north temperate species which exhibit different life-history strategies. Males spent an equal or greater amount of time incubating, yet maintained lower egg temperatures than females during different age-specific stages of the incubation period. Despite sex differences in incubation temperatures, males rewarmed cold clutches at similar rates to females suggesting similar sex-specific physiological incubation abilities. For the first time in a nidicolous species, we found that temperatures experienced by developing embryos increased with age of eggs independent of male and female time spent on the nest. Our results suggest that males may benefit embryo development by minimizing time eggs experience cold temperatures during female absences, and concurrently benefit female physiological condition for future nesting efforts. Lastly, we report standardized measures of reproductive traits in these two endemic tropical species in hope of improving data collection efforts outside of North America. Standardized measures of reproductive traits are essential for improving our understanding of reproductive biology and avian life-history evolution among different regions of the world. The Tropical Andes are among one of the most species-rich areas in the world and represent an area of critical conservation concern. Yet, for many endemic taxa inhabiting this region even basic descriptions of reproductive traits are entirely absent. This study extends the range of variation in reproductive strategies among a broader range of species among geographical regions.

Prairie is one of the most imperiled ecosystems, and grassland birds have experienced steeper and more consistent declines than any other group of birds in North America. Habitat-based planning tools are a cornerstone of conservation in forested ecosystems, but remain a novel approach in grasslands. In Chapter 2, I develop spatially-explicit habitat models as decision support tools for conservation. I survey birds, measure local vegetation and quantify landscape features at 952 sites in western Minnesota and northwest Iowa. Findings indicate that cropland provides little habitat for grassland songbirds and that hayland does not compensate for loss of grasslands. Multiscale models show that conservation actions that integrate management at local and landscape scales have the greatest chance of success. At landscape scales, conserving and creating grasslands, removing trees from the landscape, or both, increase songbird density. Density of many species is positively related to amount of grassland at the smallest scale evaluated (0.5km2), but large grasslands are vital for others whose density is related to grassland abundance at large scales (32km2). At local scales, managing for a mosaic of vegetation that varies in structure and composition increases bird diversity. Model validation shows that planning maps can be used reliably (r2 ≥ 0.90) to establish a regional conservation strategy. I used spatially-explicit maps to identify five landscapes capable of attracting the highest densities of the greatest number of songbirds, and show that most of this habitat is unprotected from risk of conversion to other land uses. Models in Chapter 2 confirm that woody edges exacerbate effects of habitat loss, so in Chapter 3 I test whether birds use otherwise suitable habitats by experimentally removing trees in a before-after/control-impact design. This is the first study to experimentally show that songbirds avoid woody edges in otherwise suitable habitat. Avoidance of trees is apparent as far away from woody edges as surveys were conducted (240m). The spring following tree removal, the four most common species redistributed themselves ubiquitously in grasslands where trees were removed. I recommend that managers remove trees from grasslands and avoid planting trees in grasslands where conservation of songbirds is the management goal.