Predation is the leading cause of nest failure in songbirds. My study identified nest predators of black-capped vireos and white-eyed vireos, quantified the activity of potential predator species, examined the relationships between vegetation and nest predators, and examined the relationship between nest predation and parasitism by brown-headed cowbirds. In 2008 and 2009 I monitored black-capped and white-eyed vireo nests on privately-owned properties in Coryell County and black-capped vireo nests on Kerr WMA in Kerr County and at Devils River State Natural Area in Val Verde County (2009 only). I monitored vireo nests using a video camera system to identify predators and nest fate. I also collected at-nest vegetation measurements including nest height, distance to nearest habitat edge, and nest concealment. Additionally, I sampled potential predator activity at a subset of black-capped vireo and white-eyed vireo nests in Coryell County using camera-trap bait stations and herptofaunal traps. I monitored 117 black-capped vireo nests and 54 white-eyed vireo nests. Forty-two percent of black-capped vireo and 35% of white-eyed vireo nests failed due to predation. I recorded >10 total predator species and 37 black-capped vireo and 15 white-eyed vireo nest predation events. Snakes (35%) and cowbirds (29%) were the most frequently identified nest predators; however, major predator species varied by location. I observed no significant relationship between nest fate (fledge vs. fail) and nest concealment or distance to edge for either vireo species. Nest height, concealment and distance to edge may relate to predator species in Coryell Co. for snake species, and Kerr for avian species. Additionally, I observed no difference between the predator activity and the fate of the nest. Both vireos have multiple nest predator species. Additionally, multiple cowbird predations demonstrate this species may have multi-level impacts on vireo productivity, even with active cowbird management. Vegetation structure and concealment may also affect predator species. However, the activity of other predator species near active nests may not negatively affect nest success.

Texas A&M University (TAMU) supports a substantial breeding population of mourning doves (Zenaida macroura) with one of the highest nest densities in Texas. There has been a long history of mourning dove research on the TAMU Campus, with initial population studies conducted in the 1950’s, and the most recent studies occurring in the 1980’s. The TAMU Campus and surrounding areas have experienced substantial changes associated with urbanization and expansion over the last 50 years, altering mourning dove habitat on and around campus. The objective of this study was to examine mourning dove nesting and production in an urban setting and determine how microhabitat and landscape features affect nest-site selection and nest success. Specifically, I (1) examined trends in mourning dove nesting density and nest success on the TAMU Campus, and (2) identified important microhabitat and landscape features associated with nest-site selection and nesting success. Mourning dove nests were located by systematically searching potential nest sites on a weekly basis from the late-March through mid-September. Nests were monitored until they either failed or successfully fledged at least 1 young. A total of 778 nests was located and monitored on campus. All nest locations were entered into ArcView GIS. An equal number of nests were randomly generated in ArcView and assigned to non-nest trees to evaluate habitat variables associated with nest-site selection for mourning doves. Binary logistic regression was used to evaluate the significance of microhabitat and landscape variables to nest-site selection and nest success. Comparisons with data collected in 1950, 1978, and 1979 showed relatively similar nesting densities, but a significant decrease in nest success over time. A comparison of microhabitat features between actual nest trees and random locations (non-nest trees) indicated increasing values of tree diameter at breast height and tree species were important predictors of mourning dove nest-site selection. Landscape features found important in dove nest-site selection were proximity to open fields, roads, and buildings. Proximity to roads and buildings also were significant predictors of nest success. Combining significant microhabitat and landscape variables for nest-site selection increased the predictability of the model indicating a possible hierarchical nest-site selection strategy.

Predation is an important ecological process that shapes life-history traits, community dynamics, and species coexistence and therefore has been suggested to explain many patterns in avian ecology. Although many studies have reported spatial, temporal, or interspecific patterns in nest predation, relatively few studies have been designed to identify the specific mechanism(s) that underlie these patterns. I examined mechanisms underlying the risk of nest predation in birds by (1) reviewing nine of the most commonly cited hypotheses to explain spatial, temporal, and interspecific variation in the risk of nest predation, (2) conducting a comparative analysis of the nest-concealment hypothesis to examine which methodological issues, extrinsic factors, and species traits influence whether or not foliage density affects the risk of nest predation, and (3) testing six mechanistic hypotheses to determine the underlying cause(s) of intra-seasonal decreases in the risk of nest predation.Many of the hypotheses invoked to explain spatial, temporal, and interspecific variation in the risk of nest predation lack clearly defined mechanisms. I suggest that future studies explicitly define the mechanism and assumption(s) of each hypothesis prior to implementing empirical tests.I found that the discrepancy in results among past studies that have examined the nest-concealment hypothesis was due to interspecific differences in a variety of intrinsic and extrinsic factors that affect nest predation but have previously been ignored. The effects of nest concealment on nest placement and probability of nest predation vary among species and this variation is predictable based on the bird's morphological traits and characteristics of the ecosystem.Increased risk of nest predation early in the breeding season appears to be due, in part, to foliage phenology and spatial and temporal changes in predator behavior. The risk of nest predation was negatively associated with foliage density early, but not late, in the breeding season. Supplemental food provided to nest predators resulted in a numerical response by nest predators, increasing the risk of nest predation at nests located near feeders. I show that intra-seasonal changes in environmental features and predator behavior affect patterns of nest predation, which can influence timing of breeding.

Mottled ducks (Anas fulvigula) are a non-migratory waterfowl species endemic to the western Gulf Coast, with a separate, genetically distinct subspecies (A. fulvigula fulvigula) occurring in peninsular Florida. Birds from Texas, Louisiana, and Florida were released in coastal South Carolina from 1975-1983, and banding data suggest an expanding population. I monitored 72 mottled duck nests and captured and radio-marked 196 pre-breeding and nesting females between 2010 and 2014 to study breeding ecology of these birds in the Ashepoo, Combahee, Edisto Rivers Basin. Nest success averaged 12% and varied with vegetation height and year. Indicated breeding pair surveys revealed breeding mottled ducks select managed wetland impoundments, predominately influenced by water depth. Future research should investigate ecology of nest predators of mottled ducks to devise successful habitat management strategies for breeding birds. Preliminary evidence suggests that managed wetland impoundments are important to breeding and brood rearing mottled ducks in coastal South Carolina.

Grassland birds are the most rapidly declining bird guild in North America, due in large part to extensive loss and fragmentation of grassland habitat resulting from the spread of agriculture and other human-dominated landscapes. Over the past several decades, grassland birds have increasingly become a guild of high conservation and management interest as their populations continue to decline and suitable grassland habitat becomes continually scarcer. Although studies investigating grassland bird responses to management actions and habitat structure are common, few studies are concerned with clarifying the mechanisms through which habitat structure may affect grassland birds. Filling this knowledge gap is critical for increasing our understanding of grassland bird ecology and improving the effectiveness of management and restoration actions for grassland birds. To address this knowledge gap, I took a uniquely holistic approach to traditional grassland bird-habitat studies by concurrently gathering data on multiple wildlife taxa that may interact with birds to examine how these different taxa respond to habitat characteristics across multiple spatial scales, and how those responses may in turn impact grassland birds. Research was conducted on 10 grassland sites at Burning Star State Wildlife Management Area in northeast Jackson County, Illinois, during the bird breeding season (May-July) from 2018 to 2021. My first five objectives were to determine the grassland habitat characteristics that were most highly associated with the following taxa: arthropods, an important food source for adult and nestling grassland birds; small mammals, which are occasional nest predators and an alternate prey source for more prolific nest predators; snakes; raccoons; and grassland birds. My final objective was to estimate the extent to which grassland bird habitat associations were mediated through nest predator abundance, alternate prey abundance, and food availability. In Chapter 2, I examined associations between grassland arthropod communities and habitat characteristics representing three spatial scales: local (within-patch vegetation structure and composition), patch (size, shape, edge composition), and landscape (landcover composition within a 400 m buffer). In addition to their relevance for grassland birds, arthropods play important functional roles in grasslands and are useful indicators of grassland health. I collected arthropod samples using pan traps in grassland patches at Burning Star, and used generalized linear mixed models to relate variation in arthropod biomass and diversity to habitat predictor variables. I found that arthropod biomass increased with vegetation height at the local scale and proportion of forest/shrub edge at the patch scale, while arthropod diversity responded only to local-scale variables, including a negative association with vegetation height and woody vegetation cover, and a positive association with forb cover. I conclude that local vegetation structure and composition are the main drivers shaping arthropod communities at Burning Star, and that limiting woody encroachment and increasing forb cover and variation in vegetation height within grassland patches may encourage arthropod abundance and diversity in tallgrass prairies. In Chapter 3, I estimated associations between small mammal abundance and habitat variables, again representing three spatial scales. I surveyed small mammal communities using a grid of 100 Sherman traps set out for three nights at each study site. I identified all captured individuals to genus, individually marked them with ear tags, and estimated abundance using a combination of Huggins P and C models in Program Mark and generalized linear mixed models in Program R. I found that small mammal abundance was positively related to vegetation density and negatively related to plant diversity, though variation in plant diversity affected Microtus voles more strongly than Peromyscus mice. At the landscape scale, small mammal abundance was positively associated with the amount of water surrounding a patch, and negatively associated with the amount of grassland surrounding a patch. Variation in small mammal community composition (proportions of Microtus vs Peromyscus) was mostly governed by differences in habitat structure at the landscape scale, rather than differences in vegetation structure at the local scale. I suggest that managers interested in influencing small mammal abundance in grasslands encourage dense vegetation growth by limiting disturbance if increased small mammal abundance is desired, or reduce vegetation density by increasing disturbance frequency to reduce small mammal abundance. Additionally, increasing plant diversity by sowing a high diversity of seeds may be an effective way to control Microtus vole populations. In Chapter 4, I estimated the habitat associations of snakes at Burning Star, focusing on the relative abundance of snakes among different grassland sites, as well as snake diversity and species-specific occupancy. Although snakes are prolific nest predators of grassland birds, they are also integral components of grassland systems, and there may be instances where managers and decision-makers wish to increase, rather than decrease, their abundance in grasslands. I found that snake community metrics were strongly and positively related to an increase in woody plant cover at the local (within-patch) scale. Snake relative abundance was also positively related to an increase in grass cover and a decrease in forb cover, though my occupancy results suggest that this was primarily driven by an increase in black kingsnakes (Lampropeltis nigra). At the patch scale, snake relative abundance and diversity were both positively related to the proportion of patch edge composed of roads. Habitat structure at the landscape scale had the smallest impact on snakes in this study, though the proportion of trees in the landscape was positively related to snake diversity. I suggested that managers and conservationists interested in manipulating snake abundance in grasslands focus on within-patch vegetation structure and composition. Decreasing woody cover in grasslands, or increasing the ratio of forbs to grasses, may reduce the presence of snakes, while maintaining a woody component could encourage both snake abundance and diversity. In Chapter 5, I estimated the habitat characteristics that were most strongly associated with raccoon abundance estimates in grassland patches at Burning Star. Raccoons have become increasingly important avian nest predators in midwestern grasslands due to rampant habitat fragmentation. I estimated raccoon abundance using an occurrence index from a series of baited trail cameras located in grassland sites. I found no convincing evidence of raccoon abundance being influenced by local scale habitat structure, beyond a weak association with vegetation height. At the patch scale, raccoon abundance was positively related to the proportion of patch edge composed of roads. At the landscape scale, raccoon abundance was negatively related to grassland, and positively related to water, within 400 meters of a grassland patch. I recommended that managers concerned with minimizing the presence of raccoons in grasslands should limit roads along grassland perimeters, maximize the proportion of grassland in the landscape surrounding a grassland patch, and avoid planning a grassland restoration in close proximity to open water if possible. In Chapter 6, I estimated the habitat characteristics that were most strongly associated with daily nest survival, nest density, and abundance of Dickcissels (Spiza americana), Field Sparrows (Spizella pusilla), and Common Yellowthroats (Geothlypis trichas), but also considered responses of all grassland bird species combined. I considered habitat characteristics representing four spatial scales: nest site, within-patch, patch, and landscape, though the nest site scale was only considered for nest survival analyses. I found that Dickcissels, an obligate grassland species, exhibited the strongest response to fire, as nest density drastically improved after previously undisturbed grasslands were burned. Dickcissel abundance was positively related to agriculture at the landscape scale and negatively related to woody cover. Field sparrows demonstrated a preference for woody cover and proximity to forests and shrublands, and Common Yellowthroats were positively associated with forb cover. Both Field Sparrow and Common Yellowthroat nest survival increased with greater distance from an edge, though no edge effect was detected for Dickcissel nest survival. All bird species benefitted from increased plant diversity and greater patch size. All species also responded negatively to vegetation height or litter depth, suggesting that fire, which reduces vegetation biomass and litter, may indirectly benefit the facultative grassland birds of Burning Star in addition to Dickcissels. In Chapter 7, I used structural equation models and data gathered in the previous five chapters to estimate whether the effects of habitat structure on breeding Field Sparrows is mediated through changes in predator (snake and raccoon) abundance, alternate prey availability, or arthropod biomass. I used Field Sparrows as the focal species for this chapter because they were the most common grassland bird in my dataset. I found no evidence of nest survival or nest density of Field Sparrows being directly influenced by nest predator abundance, alternate prey, or arthropod biomass, although habitat characteristics associated with increased nest survival were also associated with greater arthropod biomass and reduced predator abundance. I suggested that habitat structure at Burning Star may primarily impact breeding Field Sparrows through direct means, such as influencing nest concealment or foraging efficiency. These results also suggest that nest success and nest density are decoupled in this study area, so Field Sparrows may be preferentially selecting nest sites with structural characteristics that do not increase nest survival. Ultimately, my findings from this study indicate that while predator avoidance and food provisioning likely play an important role in determining nest survival for grassland birds, predator abundance and arthropod biomass may not necessarily predict predation risk and foraging efficiency to the extent that is often assumed.

No description available.

Nesting and early life is a period of high mortality for many turtle species, so understanding how turtles select nest sites, and how those nest sites impact hatching success, may be important for successful species conservation. In this research, my objective was to 1) understand how the environment around potential nest sites (canopy, understory, and soil) influences gopher tortoise nest-site selection at burrows and 2) how that nest environment both directly (nest microclimate: temperature and moisture) and indirectly (nest characteristics: nest depth, distance from burrow, canopy and understory cover, percent clay in soil, and lay date) affects hatching success in naturally incubated tortoise nests. In the summers of 2022 and 2023, I conducted repeated searches at burrows to locate nests at the Jones Center at Ichauway and the Greenwood Ecological Reserve in southwestern Georgia. I collected soil samples, measured canopy and ground cover at gopher tortoise nest locations (n=132) and an equal number of comparison non-nest burrows. At nest sites, I also monitored temperature and moisture throughout incubation. To evaluate nest-site selection, I compared burrows with and without nests using multiple logistic regression to create a suite of five biologically relevant candidate models and compared models with Akaike's Information Criterion adjusted for small sample sizes. The top three models identified canopy cover and understory vegetation cover as the only significant predictors of nest presence at burrows, with tortoises in the sites nesting at burrows with lower understory and canopy cover. Furthermore, there was an interaction between the understory vegetation and canopy cover effects, where the effect of understory cover decreased as canopy cover increased. This suggests that the vegetation effect may be primarily driven by an avoidance of shade, whereby nests laid in burrows with high canopy cover were so shaded that understory vegetation had a weaker influence on nest-site selection. When tortoises nested in burrows with lower canopy cover, which was far more common than high canopy cover at our sites, they also avoided understory vegetation so that nest sites were least shaded. These results suggest that maintaining habitats with very open overstories may be most important for allowing gopher tortoises access to preferred nest sites. To quantify the direct and indirect effects of nest environment on hatching success, I built a structural equation model (SEM) in a Bayesian framework in which hatching success was affected by nest temperature and moisture, which were themselves affected by nest site characteristics. I found that nest microclimate could be predicted moderately well from characteristics of the nest environment (R2=0.25-0.49), with lay date influencing both temperature and moisture, vegetation affecting temperature, nest position influencing moisture and temperature variability, and percent clay in soil influencing moisture. Hatching success was highest at lower mean temperatures and moistures and at intermediate levels of temperature and moisture variability, but the ability of this model to predict hatching success was low (R2=0.10). I observed very high hatching success (87.5%) and, thus, eggs were generally receiving the conditions they needed to successfully develop and there was not much variation in hatching success to explain. This framework may be useful for investigating environmental causes of lower hatching success at less robust tortoise populations that may be experiencing low rates of natural hatching success. / Master of Science / Many turtle species experience high rates of mortality in early life, so understanding how turtles select areas to nest, and how those places impact hatching success, may be important for successful species conservation. In this research, my objective was to 1) understand how the environment around potential nest locations (vegetation and soil) influences where gopher tortoise place nests at burrows and 2) how the conditions of that nest location both directly and indirectly affect hatching success in natural gopher tortoise (Gopherus polyphemus) nests. In the summers of 2022 and 2023, I conducted repeated searches at burrows to locate nests at the Jones Center at Ichauway and the Greenwood Ecological Reserve in southwestern Georgia. I collected soil samples, measured canopy and vegetative ground cover at gopher tortoise nest locations and an equal number of burrows without nests. At nest sites, I also monitored temperature and moisture throughout incubation. To evaluate how tortoises chose nest locations, I created models to compare tortoise burrows with nests to burrows that were available for nesting, but where no nest was placed. The top three models identified canopy cover and understory vegetation cover as the only significant predictors of nest presence at burrows, with tortoises in my sites nesting at burrows with lower understory and canopy cover. Furthermore, there was an interaction between the understory vegetation and canopy cover effects, where the effect of understory cover decreased as canopy cover increased. This suggests that the vegetation effect may be primarily driven by an avoidance of shade, whereby nests laid in burrows with high canopy cover were so shaded that understory vegetation had a weaker influence on nest-site selection. When tortoises nested in burrows with lower canopy cover, which was far more common than high canopy cover at my sites, they also avoided understory vegetation so that nest sites were least shaded. These results suggest that maintaining habitats with open overstories may be most important for allowing gopher tortoises access to preferred nest sites. To quantify the direct and indirect effects of nest environment on hatching success, I built a structural equation model (SEM) in which hatching success was predicted by nest temperature and moisture, which were themselves predicted by nest-site characteristics. This allowed me to evaluate both the direct effects of nest temperature and soil and the indirect pathways by which nest environment may be influencing hatching success. I found that nest temperature and moisture could be predicted moderately well from characteristics of the nest environment (R2=0.25-0.49), with the date the nest was laid influencing both temperature and moisture, vegetation around the nest affecting temperature, nest position influencing moisture and temperature variability, and percent clay in soil influencing moisture. Hatching success was highest at lower mean temperatures and moistures and at intermediate levels of temperature and moisture variability, but the ability of this model to predict hatching success was low (R2=0.10). I observed very high hatching success (87.5%) and, thus, eggs were generally receiving the conditions they needed to successfully develop and there was not much variation in hatching success to explain. This framework may be useful for investigating environmental causes of lower hatching success at less robust tortoise populations that may be experiencing low rates of natural hatching success.

The goal of this master thesis was to evaluate the field of Smart home applications run on mobile platforms such as smart phones. This was at the time a relatively new field that has attracted the attention of Smart phone giants like Apple and Google. This raised the question whether or not the users willingness to embrace the technology. To evaluate the field, a literature study was conducted covering the Smart home technology, and Apple’s and Google’s Smart home solutions. The rendered in a prototype for a Smart home communication application which was run on the Android platform. The prototype was then used in user tests focusing on the usability of the application and the field of Smart home smart phone applications. Even though the usability of the application was regarded fairly low, positive results were obtained regarding the evaluation of the field it self. This points to promising progress of Smart home applications run on smart phones.

Rio Grande wild turkey (Meleagris gallopavo intermedia) numbers in the southeastern region of the Edwards Plateau (EP) have shown a significant decline since the 1970s; however, the remainder of the EP had stable populations during this period. Since 2001, research has been conducted in the southeastern EP evaluating factors which could be responsible for the decline of Rio Grande turkeys in this region of Texas. I used digital cameras to evaluate the effect of nest predation on the reproductive success of Rio Grande wild turkeys in the region. Nest predation was the leading cause of nest loss in my study and I documented frequent predation events involving ≥1 predator species. While studying nest predation, I examined the effects of my methods, and those commonly used by others, on nest success. Nests with cameras failed at the same frequency as those without cameras but at a faster rate. Predation rates observed for artificial nests underestimated predation rates of real nests. Additionally, I photographed known turkey nest predators at 27% of random points with no eggs, suggesting that nest predation could be a random process depending on the nest predator’s unique search image. I also examined the spatial structure of the habitat surrounding nest locations of turkeys on my study sites to evaluate the effect of disturbance on nest-site selection. Out of 59 nests located on the Kerr Wildlife Management Area from 2005 through 2007, only 5 were in areas that had not been burned in the 9 years prior. Turkeys in my study consistently chose areas characteristic of the fire maintained, oak–juniper savanna historically found in the region.

Presentations of three potential nest intruders were used to investigate house wren nest defense behavior, while regular nest box checks provided information regarding house wren nest-destroying behavior. During nest defense trials, male wrens were typically more active in defense than females in the egg stage but no intersexual differences existed in the nestling stage. Males' greater defensiveness could be an extension of their territory defense role. Defense vocalizations were sex biased, with males giving primarily song calls and females giving chatter calls. Both sexes maintained or lowered their defense levels from egg to nestling stage, possibly due to decreased offspring vulnerability. House wrens altered their defense behaviors among intruder species, depending on the type of threat. Males exhibited greater defense levels against the house wren model compared to the bluebird or cowbird model in the egg stage but showed no differences among model species in the nestling stage. Females exhibited no defense differences among model species. Male defense levels were affected by their breeding strategy, as attentive males were more aggressive toward the house wren and cowbird models than non-attentive males. Attentive males discriminated among intruder species while non-attentive males did not. Lack of male attentiveness, due to polygamy or attempted polygamy, appeared to be potentially costly to females, regardless of their order of pairing with the male. House wren nest destroying behavior (NDB) varied with respect to the timing of house wren nest attacks, the abandonment and reacquisition of nests following a wren attack, and the status of neighboring house wren nests at the time of a nest attack. Some supportive evidence was found for the existing NDB hypotheses, but no single hypothesis was completely supported. House wren NDB may serve several functions but may ultimately depend on house wren population density. / Department of Educational Leadership