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Diurnal avian antipredator behavior has been the focus of much past research, yet the influence of the thermal environment on such behaviors is often overlooked. Far less is known about nocturnal avian antipredator behavior, including how these behaviors are influenced by challenging thermal environments. The first portion of my research focused on how the thermal environment influences the diurnal antipredator behavior of wintering birds while (i) exposed to high wind speeds, (ii) foraging in sunlit and shaded microhabitats, and (iii) when using thermoregulatory postures to conserve body heat. In addition to increasing convective heat loss, high wind speeds increase the prevalence of background movements in the environment. My research demonstrated that wintering sparrows exposed to a moving stimulus are less likely to flush to cover on windy days than on calm days, suggesting that wind-driven visual noise may interfere with predator detection. Predator detection may also vary when feeding in sunlight and shade, and the thermal benefits of foraging in direct sunlight on cold winter days may also play an important role in dictating microhabitat choice. Regardless of the thermal benefits of foraging in sunlight, wintering sparrows preferred to feed in shaded microhabitats even at ambient temperatures well below thermoneutrality. However, these birds foraged in sunlight more frequently as ambient temperatures fell, suggesting a trade-off between thermoregulation (solar input) and predation risk. Additional evidence of such a thermoregulation-predation trade-off was evident in the use of heat-conserving thermoregulatory postures by wintering sparrows. Fluffing the feathers or standing on one foot will reduce the amount of heat lost to the environment. However, such postures slow take-off time and likely result in an increase in predation risk. As such, these risky postures were only used when feeding at relatively low ambient temperatures and when near protective cover. In general, these results indicate that characteristics of the thermal environment play an important role in dictating diurnal antipredator behavior. To address how the thermal environment influences nocturnal avian antipredator behavior, I examined the predation-related costs of using energy-saving nocturnal hypothermia. Many species of birds reduce their nighttime body temperature, thus reducing metabolic rate and conserving energy. Such drops in body temperature may be quite substantial and likely influence a bird’s ability to respond to a potential threat during the night. To examine the potential costs of hypothermia, I conducted nocturnal flight tests on hypothermic mourning doves (Zenaida macroura). In general, doves that cooled by more than 5 °C flew poorly or were unable to fly, but were able to fly well once re-warmed to near their normal daytime body temperatures. Thus, low body temperatures during energy-saving hypothermia likely result in an increase in the risk of nocturnal predation. Nocturnal antipredator behavior was also examined in ruby-throated hummingbirds (Archilochus colubris). These hummingbirds frequently use nocturnal torpor (i.e., deep hypothermia), with significant reductions in body temperature and corresponding inability to respond behaviorally to external stimuli. Although hummingbirds altered torpor use seasonally and over the course of the observation period, hummingbirds did not consistently reduce their use of torpor following an experimental increase in perceived predation risk. Thus, although hypothermia is behaviorally costly, further studies are needed to clarify the role of predation on nocturnal behavior in birds.

In the southern Appalachians there are few data on the roost ecology of the federally endangered Indiana bat (Myotis sodalis). During 2008-2012, we investigated roosting ecology of the Indiana bat in ~280,000 ha in the Great Smoky Mountains National Park, Cherokee National Forest, and Nantahala National Forest in the southern Appalachians Mountains of Tennessee and North Carolina. We investigated 2 aspects of the Indiana bat’s roosting ecology: thermoregulation and the extrinsic factors that influence body temperature, and landscape-scale roost selection. To investigate thermoregulation of bats at roost, we used data gathered in 2012 from 6 female Indiana bats (5 adults and 1 juvenile) to examine how reproductive condition, group size, roost characteristics, air temperature, and barometric pressure related to body temperature of roosting bats. We found that air temperature was the primary factor correlated with bats’ body temperatures while at roost (P < 0.01), with few differences detected among reproductive classes in terms of thermoregulatory strategies. To understand how Indiana bats select roosts on a landscape-scale, we created a presence-only model through the program MaxENT using 76 known roost locations to identify areas important to summer roosting habitat within our study area and to identify important landscape-scale factors in habitat selection. The final model showed that Indiana bats selected roosts on the upper portion of ridges on south facing slopes in mixed pine-hardwood forests at elevations of 260-700 meters. Unfortunately, due to small sample size and the large effort required to fully investigate thermoregulation of Indiana bats in the southern Appalachians, we only were able run correlations with temperature data, and further investigation is needed to make concrete conclusions. However, the new advancements in resolution of landscape cover data and new programs in spatial modeling have enabled us to produce a large scale spatial model for identifying Indiana bat summer roosting habitat within our study area. Our findings have added to our understanding of Indiana bat roosting ecology, particularly in the southern Appalachian Mountains, and will aid land managers in effective management for this federally endangered species.

Phenotype is affected by many factors, including but not limited to environment, conspecifics, and genetics. Evidence of phenotypic variation is everywhere, some of which is controlled solely by environment, and others that are fixed by genetics. Genetic polymorphisms are rare, but very useful for the study of selection and genetics. These genetic polymorphisms provide a phenotypic link to the underlying genetics and are even more useful when there are associated behavioral differences. I examine multiple levels of selection that are acting upon a polymorphic passerine, the white-throated sparrow (Zonotrichia albicollis). Males and females of this species occur in two morphs, white or tan, based upon the color of their crown strips. This plumage polymorphism is absolutely correlated with a complex chromosomal rearrangement on the second largest autosome. Within this dissertation I explore how climate needs to be addressed in ecological studies to fully understand the mechanisms behind variation. I explore whether sexual selection is acting within this species and the differences between the morphs through the use of Bateman Gradients. Darwin suggested that sex ratios influence sexual selection, but what about morph ratios? I examine the frequency variation of morphs within this species. Variation in morph production may be favored by a potential tradeoff between the number of males and the number of white offspring produced in a clutch that suggests greater costs associated with producing white morph individuals. Mendelian segregation is inconsistent in this species, and transmission distortion may contribute to morph ratio variation. I show that white male sperm varies in production from 0% - 100% white sperm/individual consistent with transmission distortion. Finally, candidate gene mapping was used to identify the genes sequestered in this rearrangement that may be responsible for the polymorphism and the evolution behind the rearrangement.

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