<p>The Golden-winged Warbler (Vermivora chrysoptera) is an imperiled songbird that breeds in early-successional plant communities of eastern North America. Conservation efforts on the breeding grounds have become a priority because population declines are understood to be driven chiefly by the loss/degradation of breeding habitat. Although the species is known to use a variety of upland and wetland habitat types, most previous research on the species has been conducted solely in uplands. I studied Golden-winged Warbler use and habitat characteristics in the Poconos region of Pennsylvania. Density estimates suggest that both timber harvests and wetlands support similar densities of Golden-winged Warblers. Microhabitat occupancy models revealed that those wetlands I surveyed with high densities of 1-2 m tall shrubs (>2x as many shrubs) supported fewer Golden-winged Warblers whereas wetlands with more saplings (>2x as many saplings) and sedge cover (~1.3x as many sedge observations) supported more warblers. Finally, I found that macro-scale habitat variables that I quantified did not predict species occupancy of wetlands, likely due to the homogeneous nature of the study area. My study suggests that both wetlands and timber harvests have similar capacity to support Golden-winged Warblers. Further, wetlands in the Poconos should be evaluated at the microhabitat-scale for vegetative attributes that meet Golden-winged Warbler habitat requirements, rather than at the macro-habitat scale.

<p> Sea-level rise is a concern for the future of coastal marsh obligate species such as the Clapper Rail (<i>Rallus crepitans</i>). Clapper Rails possess the potential to indicate changes to marsh ecological state due to population variation related to habitat features exhibited in previous study. Estimates for Clapper Rail survival are among the key missing parameters to create predictive models for Clapper Rail populations. I estimated Clapper Rail survival using data collected from six automated telemetry towers located in two Mississippi marshes. Thirty adult rails were harnessed with radio transmitters around telemetry towers to provide evidence of a rail&rsquo;s status, alive or dead. Using survival estimates in conjunction with existing empirical data, I created an individual-based model that incorporated existing Sea-level Affecting Marsh Models, which predict changing land cover. These models showed that Clapper Rails will likely persist, though at decreased populations, through changes in habitat due to sea-level rise.</p><p>

<p> Historically, black bears occurred throughout Mississippi but by 1932, &lt;12 bears remained. Repatriation in neighboring states and conservation efforts in Mississippi have led to the recolonization of at least 2 subspecies (<i>U. a. luteolus</i> and <i>U. a. americanus</i>) of black bears in the state. I compiled available data to provide a synthesis of the history, current status, and management of black bears in Mississippi. Additionally, I used global positioning data collected from radio collared bears to determine the influence of distance to source population, cover type, distance to roads, distance to water, wetland reserve program areas, and human population density on black bear resource selection at various spatial scales. I studied characteristics of space use and resource selection of recolonizing bears in the Mississippi Alluvial Valley (Delta). I assessed the influence of environmental parameters at the female core annual home-range (using 50% kernel density estimator) and male and female seasonal and annual home-ranges (95% kernel density estimator). Distance to source population and distance to roads had significant influence at the core female home-range scale. I found a sex-based difference in annual and seasonal home-ranges. I also found that bears exhibited response to and selection for specific resources with an affinity toward hardwood stands, particularly young-aged hardwoods. My research illustrates the importance of analyzing resource selection at multiple scales to gain a full understanding of parameters that influence the recolonization of a bear population.</p><p>

<p> Rails (Family: Rallidae) are among the least studied birds in North America, in large part due to their elusive nature. As a wetland-dependent species, understanding the timing of their migration and their habitat needs during migration is especially important since management needs to be timed to balance the needs of many species. I developed and verified a new distance sampling based nocturnal ATV spotlight survey because traditional call-broadcast surveys are not effective during autumn migration because of the drop off in call rate after the breeding season. These surveys allow us to ask point-level questions about what habitats rails select during migration and how it changes over time. Through these standardized surveys from 2012-2016 across 11 public properties in Missouri, USA, I documented the migratory timing and habitat use of migratory rails. Sora (Porzana carolina) have a wide migratory window, beginning in early August and continuing through the end of October with a peak in late September. Virginia Rail (Rallus limicola) and Yellow Rails (Coturnicops noveboracensis) have shorter migratory periods, from late September through the end of October. Rails, especially Sora, migrate earlier than waterfowl, which can create a mismatch of habitat needs. We performed a 3 year experiment to examine the response of Sora and waterfowl to early autumn wetland flooding. Sora responded positively without a negative impact on waterfowl. I used monitoring data to create species distribution models to inform estimates of migratory connectivity for all three species using stable hydrogen isotopes. Sora and Yellow Rails were estimated to migrate generally north-south, with Virginia Rails coming from a wider east-west range. Through better understanding the migratory connectivity, timing and habitat use of rails in the autumn I provide a foundation to inform conservation and management of these fascinating and elusive birds. We provide a description of all variables used (Appendix II), GPS data of survey tracks and detection points (Appendix III), data sets of bird observation points, survey data, and vegetation information (Appendix IV), data sets of stable hydrogen isotope data (Appendix V), data sets of species distribution models (Appendix VI).</p>

<p> The Pacific Coast population of the western snowy plover (<i>Charadrius nivosus</i> nivosus; plover) is listed as a federally threatened species under the U.S. Endangered Species Act due to poor reproductive success from anthropogenic habitat loss, and high predation pressure. Plovers in the South San Francisco Bay use dry salt evaporation ponds, and wildlife-managed ponds, to breed and winter. However, the South Bay Salt Pond Restoration Project aims to restore up to 6,110 hectares of this habitat back to native tidal marsh, which will force plovers to breed in smaller areas and in higher densities. In order to recover plovers in these unique conditions, remaining habitat can be enhanced using oyster shells, which may camouflage breeding plovers, and decrease predation. This study evaluated the effect of oyster shell enhancement on plover breeding success by comparing nesting density, success, and brood behavior between enhanced and unenhanced areas. Plovers did select to nest in enhanced areas; however, nest survival did not increase relative to unenhanced areas. Brood behavior was also affected by enhancement, though highly correlated with the location of optimal foraging habitat. It is likely that enhancement will only improve nesting success if predators are concurrently controlled. Ultimately, plovers may benefit from the application of oyster shells as it attracts nesting effort, and may be strategically used by resource managers.</p><p>

Virtually any person exposed to American movies or television has likely heard the call of a common loon (Gavia immer). Its use as a sound prop has become ubiquitous in any scene related to the outdoors or the wilderness, even if the area filmed is in no way related to true loon habitat. The reason behind this is that the common loon and its haunting cries have come to symbolize the great outdoors. The sound of their call is meant to make the audience feel like the scene they are watching is in a remote area, far from the trappings of civilization, and, in our experience, it works. Hollywood has picked up on a sentiment held by many outdoor enthusiasts and is using it successfully. Unfortunately the southern range of the common loon is contracting and concern has been expressed over disturbance to breeding pairs by human activities, such as shoreline development, boating, and water-skiing, as well as possible contamination with lead, mercury, and other pollutants. If this alarming trend continues it may be that Hollywood movies will be the last place where a loon call can be heard in the United States. In the following chapters I will explore various threats to common loon populations. I will start in Chapter 1 with an evaluation of the potential effects of global warming on common loons within the North American breeding range. In Chapter 2 I review the available literature on wildlife disturbance and discuss some of the shortcomings and future research needs. I then go to a finer scale of study in Chapter 3 with a spatial analysis of disturbance factors and the effects on breeding common loons at Lake Umbagog National Wildlife Refuge. From there, in Chapter 4, I proceed to an analysis of specific behavioral responses exhibited by common loons in response to observed and experimentally imposed disturbance events. Finally, in Chapters 5 and 6, I briefly describe two natural disturbance events observed during our research, an immature bald eagle (Haliaeetus leucocephalus) predating a loon nest, and a loon nest defense of an aggressive American mink ( Nevison vison).

The world’s biodiversity is concentrated in tropical ecosystems, yet tropical forests are being converted for agriculture at a rapid rate. I evaluated the potential of an alternative coffee production system known as Integrated Open Canopy (IOC) to contribute to avian conservation. This study was conducted from 2005–2010 in the Cordillera de Tilarán, Costa Rica. My results indicate that species richness of forest-dependent birds was significantly higher in IOC farms than in shade coffee farms, and was comparable to secondary forest sites. There was no difference in species richness of Neotropical-Nearctic migrants between IOC and shade coffee farms. Overall similarity was higher between IOC farms and primary forest than between shade coffee farms and primary forest. The golden-winged warbler (Vermivora chrysoptera) is a declining Neotropical-Nearctic migrant bird, yet little is known about its non-breeding season ecology and demographics. I found that golden-winged warbler abundance was highest at intermediate precipitation levels found at middle elevations (1000–1200 m) of the Pacific slope, but they were absent from the dry forests at lower elevations on the Pacific slope. Abundance peaked in forests with canopy heights of 22 m, and was positively related to the quantity of hanging dead leaves. Radio-telemetry data indicated that golden-winged warblers used microhabitat features characteristic of disturbance more frequently than expected by chance. Selection of these microhabitat features was related to their highly specialized dead-leaf foraging behavior, which may also have contributed to their high degrees of site fidelity, mixed-species flock attendance, and territoriality. These behaviors have important conservation implications because they constrain density, and thus could affect carrying capacity. Population dynamics were characterized by estimating plot-level and individual-level apparent survival and recruitment rates within and among non-breeding seasons. Both levels of analysis suggested that recruitment was too low to offset mortalities within this study area. This study indicates that increasing forest cover in tropical agricultural landscapes may be the most effective way of providing habitat for bird species of high conservation concern, including the golden-winged warbler. Integrated open canopy coffee production is one option for achieving this goal because it provides a financial incentive to protect or restore forest.

<p> Breeding bird surveys were conducted on 7 properties belonging to 2 ranches in South Texas. Using these data I calculated temporal trends, and tested the effects of total May&ndash;April precipitation and cattle stocking rate on avian abundance. Trends were calculated for each ranch, the East Foundation and King Ranch, individually due to different range and wildlife management practices. Total avian abundance increased significantly on the 3 East Foundation properties between 2008 and 2015. During 39 breeding bird surveys, 16,441 individual birds of 88 species were recorded. Non-breeding bird surveys were also conducted on East Foundation properties, an increasing trend in total avian abundance was also calculated from these data. Total breeding bird abundance was stable on the 4 King Ranch properties between 2005 and 2013. A total of 19,162 individual birds of 87 species were recorded during 40 breeding bird surveys. The combined effect of livestock use and precipitation had a significant effect on total avian abundance on all King Ranch properties, and on the abundance of some individual species and groups. </p>

<p> Interest in renewable energy and governmental mandates has motivated land managers to consider cellulosic feedstocks for bioenergy. I investigated plant community response to a system including switchgrass (<i> Panicum virgatum</i>) as a feedstock intercropped with loblolly pine (<i>Pinus taeda</i>). I estimated plant species evenness, richness, and diversity and biomass production, with emphasis on white-tailed deer (<i> Odocoileus virginianus</i>) forages. I detected 225 species in 2,220 1-m² quadrats, and 7,495 biomass samples (96.4 kg dry weight) from 960 quadrats. Intercropping reduced plant species diversity, total non-pine tree biomass, and biomass of deer forages during switchgrass establishment. These effects were no longer apparent at treatment level two years after switchgrass establishment, except that deer browse and total deer forage biomass remained less in intercropped interbeds. Intercropping in managed pines may temporarily effect plant communities but further studies are needed to examine longer term effects and to quantify effects on nutritional carrying capacity for deer.</p>

<p> The extent of human disturbance is increasing, even in protected areas. I evaluated human disturbance impacts in Murchison Falls Conservation Area (MFCA), Uganda, a park in the Albertine Rift biodiversity hotspot, using two approaches. First, I quantified vegetation patterns and edge effects using remote sensing data in the MFCA interior, a boundary zone, and exterior zone. I observed abrupt changes in productivity between the park and adjacent unprotected areas, indicating a "hard edge", and found evidence of edge effects that extended 4-6 km into MFCA. Second, I evaluated the impact of restored oil pads, roads, the park boundary, and anthropogenic noise on mammal distribution using camera traps and occupancy modeling. Few species avoided, and some were attracted to, more disturbed sites, where restoration may have provided food resources. As human populations continue growing around MFCA and oil production begins, evaluating human disturbance impacts on the landscape will be increasingly important.</p>