Most migrating songbirds are required to stopover to rest and replenish their fat reserves, and suitable stopover habitat is vitally important to their survival and success securing territories at their breeding and wintering grounds. Identifying and protecting stopover locations and movement corridors is essential to connecting all life stages of these species, yet there remain significant knowledge gaps regarding the utilization of stopover sites and fine-scale movements during migration, particularly at inland stopover areas. We investigated the factors that influence stopover duration and migration rate of ten migratory songbirds within the Silvio O. Conte National Fish and Wildlife Refuge in the Northeastern United States during two fall and spring seasons in 2015 and 2016 at 5 banding sites using automated telemetry. We expected that fat and mass would influence stopover duration and migration rate, in that birds with larger fat stores and greater masses would make shorter stopovers, and migrate faster than leaner birds. We also expected that birds would move faster in spring, and minimize time later in the season, by making shorter stopovers and migrating faster as the season progresses. A lower percentage of our focal species departed the banding sites within 24 hours compared to other studies in coastal and urban sites, indicating that more birds made stopovers. Sixteen percent of birds made prolonged stopovers (> 7 days) in spring, and 38 % in fall, highlighting the importance of the refuge for long term refueling. Spring birds made shorter stopovers, and traveled at faster rates than fall birds, suggesting there is may be more pressure for early arrival at breeding grounds. Spring birds captured with significant fat loads made shorter stopovers, and traveled faster than leaner birds. Spring birds also appeared to employ a time minimization strategy, with birds captured later in the season making shorter stopovers. Migration rate of spring birds decreased with distance from the capture site, indicating many birds needed to make additional stopovers. Fall birds that made longer stopovers migrated at faster rates. Fall birds captured later in the season made longer stopovers, and subsequently traveled at faster rates once they departed to possibly minimize time on migration. Variation in stopover behavior was evident among sites and species and this may suggest habitat or site characteristics that affect their value for migrating birds, which should be taken into consideration when conservation planning or vulnerable species. The extensive use of this inland National fish and wildlife refuge by migratory birds, and the fact that birds are acquiring energy reserves that are facilitating successful migration suggests this region is an important corridor for migrating songbirds.

<p>Mutations of the FOXP2 gene impair speech and language development in humans and shRNA-mediated suppression of the avian orthologue FoxP2 disrupts song learning in juvenile zebra finches. How diminished FoxP2 levels affect vocal control and alter the function of neural circuits important to learned vocalizations remains unclear. Using a combination of behavioral analysis, in vivo intracellular recordings in anaesthetized birds, pharmacology and extracellular recordings in singing birds, I addressed how FoxP2 knockdown in songbird striatum affects vocal control and signal propagation through circuits important for the control of learned vocalizations. In summary, I found that FoxP2 knockdown in the songbird striatum disrupts developmental and social modulation of song variability. Recordings in anaesthetized birds show that FoxP2 knockdown interferes with D1R-dependent modulation of activity propagation in a corticostriatal pathway important to song variability, an effect that may be partly attributable to reduced D1R and DARPP-32 protein levels. Furthermore, recordings in singing birds reveal that FoxP2 knockdown prevents social modulation of singing-related activity in this pathway. These findings show that reduced FoxP2 levels interfere with the dopaminergic modulation of vocal variability, which may impede song and speech development by disrupting reinforcement learning mechanisms.</p> / Dissertation

Doctor of Philosophy / Department of Biology / Brett K. Sandercock / Grasslands are among the most rapidly declining ecosystems in the world. The Flint Hills ecoregion contains one of the largest remaining tracts of tallgrass prairie, but most of the area is managed with high densities of grazing animals and frequent prescribed burns, thereby reducing variation in vegetative structure. A homogeneous landscape leads to lower diversity and abundance of wildlife species, including grassland songbirds. Patch-burn grazing management has been proposed to more closely match the historical interaction between fire and selective grazing by native ungulates. Pastures managed with patch-burn grazing have a greater variety of vegetative structure and plant species composition, and as a result, higher species diversity, abundance, and reproductive success of grassland birds. However, past work has not considered potential effects of regional variation in predation risk and rates of brood parasitism by Brown-headed Cowbirds (Molothrus ater), or annual variation in climatic conditions on the effects of patch-burn grazing management on the reproductive success of grassland songbirds. Over a six year period and at two tallgrass prairie sites, I tested the effects of patch-burn grazing on the reproductive success of three native grassland songbird species, Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum), as well as subsequent effects on the space use, movements, and survival of fledgling Dickcissels. I found only minor effects of patch-burn grazing on the reproductive success of grassland songbirds, supporting previous studies that show that patch-burn grazing does not have negative effects on demographic rates of grassland songbirds. Management regime did not affect densities or territory size of male Dickcissels, but bird densities tended to be higher and territories tended to be smaller on patches within the patch-burn grazing treatment that were burned in the previous year. Thus, patch-burn grazing management might benefit Dickcissel populations by providing higher quality breeding habitat in unburned patches. Last, I found evidence for a potential tradeoff between habitat selection for nests vs. fledglings of Dickcissels in some rangeland management strategies. Parents that realized high reproductive success by nesting in pastures with lower cowbird densities, produced fledglings that faced high rates of depredation by snakes and showed greater movements away from those pastures. Survival rates and movements of Dickcissel fledglings were low, especially during the first week after leaving the nest, which stresses the importance of local habitat conditions. At a larger spatial scale, I tested whether regional differences in habitat structure could drive variation in apparent survival of grassland songbirds. I found that grassland- and shrubland-breeding species had higher estimates of apparent survival than forest-breeding species, contrary to the prevailing viewpoint that birds breeding in dynamic landscapes, such as frequently burned grasslands, should show lower apparent survival than species that breed in woody habitats. The results of my field study show that restoring the historical interaction between fire and grazing on the landscape via patch-burn grazing management could benefit grassland songbirds. Moreover, my dissertation is the first study that tests the effects of patch-burn grazing management on the survival and movements of fledgling Dickcissels, and shows that high cowbird densities can cause a tradeoff between different life-stages. Future conservation efforts should take into account regional variation in species abundance, predator community composition and abundance of Brown-headed Cowbirds when assessing the effects of rangeland management on the demography of grassland songbirds.

Cognition, defined as the mechanism by which an animal acquires, processes, stores, and uses information present in the environment, is a trait that is sensitive to developmental conditions. Existing research supports the idea that the ability to develop and maintain cognitive abilities depends on the physiological condition of the individual, which can be influenced by the early environment. Alterations in maternal care, social stress, and malnutrition are some examples of environmental conditions that impact development and resulting cognitive abilities across taxa. The primary goal of this research was to determine whether immune system challenge during the critical song learning period in zebra finches (Taeniopygia guttata) would lead to long term negative impacts on song quality and learning, spatial learning, and neophobia. Immune challenge during this period of development did not produce long term impacts on learning or memory, nor did it lead to any changes in neophobic responses. However, birds that were hatched later in a clutch performed better on the motoric and spatial tasks, and were less neophobic. Future research in zebra finches that can describe the variation in song attributes as a function of hatching order would be a useful first step in determining a mechanistic link between hatch order and song learning outcomes. / Master of Science

This thesis develops a new method for time-frequency signal processing and examines the relevance of the new representation in studies of neural coding in songbirds. The method groups together associated regions of the time-frequency plane into objects defined by time-frequency contours. By combining information about structurally stable contour shapes over multiple time-scales and angles, a signal decomposition is produced that distributes resolution adaptively. As a result, distinct signal components are represented in their own most parsimonious forms.  Next, through neural recordings in singing birds, it was found that activity in song premotor cortex is significantly correlated with the objects defined by this new representation of sound. In this process, an automated way of finding sub-syllable acoustic transitions in birdsongs was first developed, and then increased spiking probability was found at the boundaries of these acoustic transitions. Finally, a new approach to study auditory cortical sequence processing more generally is proposed. In this approach, songbirds were trained to discriminate Morse-code-like sequences of clicks, and the neural correlates of this behavior were examined in primary and secondary auditory cortex. It was found that a distinct transformation of auditory responses to the sequences of clicks exists as information transferred from primary to secondary auditory areas. Neurons in secondary auditory areas respond asynchronously and selectively -- in a manner that depends on the temporal context of the click. This transformation from a temporal to a spatial representation of sound provides a possible basis for the songbird's natural ability to discriminate complex temporal sequences.

Dans de nombreuses espèces doiseaux chanteurs (ou Passériformes), dont fait partie le canari domestique (Serinus canaria), le comportement de chant est produit à la fois pour défendre un territoire ou attirer un partenaire. Le Système de Conntrôle du Chant est un réseau nerveux central spécialisé, principalement localisé au niveau du télencéphale et associé au contrôle de lapprentissage, la perception et la production du chant. Ce comportement a été décrit subir la modulation de facteurs externes, tels que la testostérone, la photopériode et les interactions sociales. En parallèle avec le comportement de chant, certains des noyaux appartenant au Système de Contrôle du Chant (HVC, RA et Area X) présentent un phénomène de plasticité saisonnière nerveuse fascinante. Le volume de ces noyaux augmente notamment par espacement des cellules, agrandissement de la taille du neuropile et de larborisation dendritique et, dans le cas particulier dHVC, par incorporation de neurones nouveaux-nés. Nous proposons ici une synthèse de la littérature concernant ce phénomène tout à fait particulier ; en effet, la régénération des neurones du système nerveux central est considérée comme inexistante -ou uniquement limitée à la production de quelques interneurones- chez les mammifères. Létude de la neuroplasticité chez loiseau chanteur constitue dès lors un modèle tout à fait remarquable et offrant des perspectives nouvelles dans létude du cerveau des vertébrés.

Stress has long lasting effects on physiology, development, behavior, reproductive success and survival. These effects are mediated by glucocorticoids, such as corticosterone (Cort), via glucocorticoid receptors (GR), though the exact mechanisms underlying these effects are unknown. Early developmental stress affects the size of the avian song control nuclei (particularly HVC; proper name) and song quality in many songbirds, suggesting a direct link between brain and behavior. HVC is required for song learning and production. The complexity of the male zebra finch (Taeniopygia guttata) courtship song is important in female mate choice. Although the mechanisms behind the effects of developmental stress on song nuclei size and song quality are unknown, it is likely that elevated levels of Cort via GR within brain song nuclei play a significant role. We investigated the distribution, quantity, and subcellular-localization of GR- immunoreactive (GR-ir) neurons in the brains of male zebra finches 10 days post-hatch and in adulthood using immunohistochemistry. There was wide distribution of GR-ir neurons including two song nuclei HVC and robust nucleus of the arcopallium (RA). Distribution did not vary between the two ages but there were significant differences in the overall number of GR-ir neurons and their subcellular localization. We hypothesized that early Cort treatment would reduce song quality and HVC size in adult males. We inserted Cort implants in males at four days post-hatch and quantified the effects of early Cort treatment on adult song quality. Early Cort treatment decreased song similarity between the tutor and tutee’s songs and resulted in poorer copies of tutor song, but did not alter mean amplitude or song duration. Early Cort treatment reduced the HVC size in both juvenile and adult birds. This result suggests that the effect of developmental stress on the HVC size may be mediated through Cort via activation of GR within HVC as a mechanism by which HVC size and song quality are altered in developmentally stressed birds. These results suggest a potential role for Cort in mediating adverse effects of developmental stress in adult male zebra finches and highlight the developmental plasticity of the zebra finch brain.

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Repeat photography, the process of retaking an existing photograph from the same vantage point, can give insight into long-term land cover dynamics. I advance the use of repeat photography to quantify landscape change in two ways: first, I demonstrate that rigorous field and post-processing methods can lead to highly accurate co-registration of images; second, I show that oblique photographs can provide land cover composition information similar to conventional satellite (Landsat) imagery for dominant land cover types, and that oblique photographs are better at resolving narrow or steep landscape features. I then present a novel approach to evaluate long-term biodiversity change using repeat photography: I measure land cover composition in 46 historical and modern photograph pairs in the Willmore Wilderness Park, Alberta, Canada, and use that land cover information as input into species-habitat models to predict the probability of occurrence of 15 songbird species. I show that coniferous forest cover increased over the past century, leading to a homogenization of the landscape which increased the probability of occurrence of forest-adapted species but negatively impacted non-forest-adapted species. / Graduate / 2019-04-18

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