No description available.

Populations of many species of migratory birds are declining, and an understanding of how populations are linked between the breeding and nonbreeding grounds is necessary in order to determine drivers of declines. While all current tracking technologies to study the movements of small songbirds are limited by their coarse resolution, tracking birds by measuring stable isotopes in keratin offers an advantage because it requires only a single capture and is cost-effective, which leads to robust sample sizes. While this tracking method is accurate, stable hydrogen isotope values measured in feathers (δ2Hf) are known to be variable within a site, and may be influenced by the hydrology of a site. In this study, we assessed sources of variation in δ2Hf values in a wetland-associated Neotropical migratory bird, the prothonotary warbler (Protonotaria citrea), by comparing δ2Hf values among ages, sexes, years and feather type. We found that age and year significantly influence δ2Hf values, and that differences between primaries and rectrices are statistically significant but generally small. We also tested the accuracy and precision of models to assign prothonotary warblers to their breeding origin using known-origin feathers. We assigned birds in a spatially-explicit manner using an interpolated surface of stable hydrogen values measured in precipitation (δ2Hp), and developed a species-specific calibration equation to account for the offset between δ2Hf and δ2Hp, which explained 51% of the variation in δ2Hf values. We incorporated breeding bird abundance as prior information in our assignment model, and compared two sources of abundance data: the Breeding Bird Survey and a spatio-temporal exploratory model developed with eBird data. The assignment model with no prior information was accurate (83% of birds correctly assigned to their true location of origin), but imprecise (50% of grid cells assigned as likely locations of origin). Incorporating abundance as prior information led to a decrease in accuracy (9-14% of birds correctly assigned) but higher precision (1% of grid cells assigned as likely). We also assigned prothonotary warblers to their breeding origin using feathers collected from across the nonbreeding range. We found that all nonbreeding sampling locations contained a mixture of birds whose origins spanned the majority of the breeding range, with no evidence of strong connectivity between the seasons. In the absence of strong connectivity, the influence of events occurring at one nonbreeding location will be widespread and diffuse across the breeding range. For prothonotary warblers, understanding connectivity can help conservation planners understand how nonbreeding season habitat destruction and other processes influence population dynamics. We recommend that future studies account for age and year variation in δ2Hf values when possible, and continue to examine the trade-off between precision gained and accuracy lost when using abundance as prior information.

No description available.

Migration is a widespread and complex phenomenon in nature that has fascinated humans for centuries. Connectivity among populations influences their demographics, genetic structure and response to environmental change. Here, I used the loggerhead turtle (Caretta caretta, L.) as a study organism to address questions related to migratory connectivity and carry-over effects using satellite telemetry, stable isotope analysis and GIS interpolation methods. Telemetry identified foraging areas previously overlooked for loggerheads nesting in Florida. Next, I validated and evaluated the efficacy of intrinsic markers as a complementary and low cost tool to assign loggerhead foraging regions in the Northwest Atlantic Ocean (NWA), using both a spatially implicit and spatially explicit (isoscapes) approach. I then focused on the nesting beaches and developed a common currency for isotopic studies based on unhatched eggs, which provide a non-invasive and non-destructive method for more extensive sampling to elucidate isotopic patterns across broader spatiotemporal scales. Lastly, I found that intra-population variations in foraging strategies affect annual and long-term reproductive output of loggerheads nesting in Florida. Understanding geospatial linkages is critical to the fostering of appropriate management and conservation strategies for migratory species. My multi-faceted approach contributes to the growing body of literature exploring migratory connectivity and carry-over effects.

Understanding migratory connectivity is essential for assessing the drivers behind population dynamics and for implementing effective management in migratory species. Genetic markers provide a means to describe migratory connectivity, as well as incorporate population genetic analyses, however genetic markers can be uninformative for species with weak genetic structure. In this study, we evaluate range-wide population genetic structure and migratory connectivity in the prothonotary warbler, Protonotaria citrea, a wetland-dependent neotropical migratory songbird, using high-resolution genetic markers. We reveal regional genetic structure between sampling sites in the Mississippi River Valley and the Atlantic Seaboard with overall weak genetic differentiation among populations (FST = 0.0051). By ranking loci by FST and using subsets of the most differentiated genetic markers (200 – 3000), we identify a maximum assignment accuracy (89.7% to site, 94.3% to region) using 600 single nucleotide polymorphisms. We assign samples from unknown origin nonbreeding sites to a breeding region, illustrating weak migratory connectivity between prothonotary warbler breeding and nonbreeding grounds. Our results highlight the importance of using high-resolution markers in studies of migratory connectivity with species exhibiting weak genetic structure. Using similar techniques, studies may begin to describe population genetic structure that was previously undocumented, allowing us to infer the migratory patterns of an increasing number of species.

Migration acts as a selective force on the ecology and evolutionary trajectory of species, as well as presenting fundamental challenges for conservation. My thesis examines the impact of migration by exploring patterns of differentiation among and within migratory and non-migratory populations of the Loggerhead Shrike (Lanius ludovicianus). First, I use morphological, genotypic, stable isotope and leg band recovery data to quantify migratory connectivity in the species. Comparison across markers reveals a generally concordant pattern of moderate connectivity to the Gulf Coast, but overall mixing among populations on the wintering grounds. Combining data from multiple markers in a Bayesian framework improves the resolution of assignment of wintering birds to a breeding ground origin. Information on the species’ migratory patterns provides an explicit framework for interpreting patterns of genetic and ecological variation. I test two hypotheses regarding the interaction of gene flow and migratory habit: (1) migration facilitates gene flow; and (2) gene flow will occur most often along the axis of migration. Genetic population structure in migratory populations is weaker than in non-migratory populations, with gene flow facilitated by dispersal movements of females and first year breeders. As predicted, gene flow occurs most often along the north-south axis of migration, likely due either to opportunistic settling of dispersers or potentially, pairing on the wintering grounds. I investigate variation in the extent and scheduling of moult in relation to underlying genetic differences among populations, age, sex, body size, food availability and migratory habit. I find a pattern of interrupted moult across migratory populations, which may represent a trade-off between time allocated to breeding versus molt and migration. Loggerhead Shrikes in eastern and more southerly migratory populations undergo a greater extent of their moult on the breeding grounds and non-migratory individuals undergo a more extensive pre-formative moult than migratory individuals. I interpret this as suggesting a trade-off between resources allocated to molt versus those required for reproduction. / Thesis (Ph.D, Biology) -- Queen's University, 2011-01-25 15:54:36.593

Le déplacement animal joue un rôle déterminant dans la structuration spatiale et la dynamique des populations biologiques, en particulier des espèces fortement mobiles. L’espace et l’environnement font ainsi partie intégrante du cycle de vie des tortues marines. Ce travail de thèse propose de caractériser l’écologie spatiale des tortues marines, du stade juvénile au stade adulte, dans le Sud-ouest de l’océan Indien, principalement par l’usage de deux méthodes : la télémétrie satellitaire et la modélisation individu-centrée. Il montre en premier lieu que la phénologie de la reproduction de la tortue verte à travers la région est principalement liée à la température de surface de la mer au voisinage des sites de reproduction. Sont ensuite étudiés les patrons de dérive des nouveau-nés générés par les courants océaniques qui impacteraient inégalement leurs traits d’histoire de vie selon l’emplacement du site de naissance. Concernant le stade immature, les résultats suggèrent un cycle de développement trans-équatorial pour la tortue caouanne dans l’océan Indien. Pour le stade adulte, cette étude caractérise les couloirs et la connectivité migratoires de la tortue verte dans la région. Enfin, l’intégration de ces résultats permet de comprendre la structuration des patrons migratoires régionaux et leur influence sur la dynamique des populations. L’ensemble des connaissances acquises fournit un support concret d’aide à la décision pour la mise en place de plans de gestion et de conservation des tortues marines dans le Sud-ouest de l’océan Indien. Cela souligne l’importance d’une approche à grande échelle pour la protection d’un patrimoine biologique partagé par plusieurs nations. / Animal movement is crucial to the ecology of spatially structured population, particularly for highly mobile species. Marine turtles’ life cycle is indeed closely related to spatial and environmental factors. This work analyses the spatial ecology of marine turtles, from early juvenile to adult stages, in the Southwest Indian Ocean, primarily through the use of two methods: satellite tracking and individual-based modeling. Firstly, this analysis argues that green turtle’s reproductive phenology across the region is mainly related to the sea surface temperature in the vicinity of the nesting site. Then, it shows how drifting trajectories of hatchlings in oceanic currents unevenly influence their life history traits depending on the position of the natal site. By tracking late juvenile stage, this work also suggests a trans-equatorial developmental cycle for loggerhead turtle in the Indian Ocean. At adult stage, it describes migratory corridors and connectivity for green turtle across the region. Finally, an integrative approach considering all these results allows for an understanding of the regional migratory patterns and their influence on population dynamics. The results of this work provide a practical policy decision tool for management and conservation of marine turtles in the Southwest Indian Ocean and highlight the need for a large-scale approach in the protection of biological resources and heritage shared by multiple nations.

Migratory insects are vital components of global ecosystems and provide important ecosystem services, yet the migration phenomenon is understudied in insects compared to vertebrates. In this thesis, I aim to deepen our understanding of insect migration, using the monarch butterfly Danaus plexippus (L.) and the painted lady butterfly Vanessa cardui (L.) as model systems. Studying insect migration is notoriously difficult given the small size, high abundance, and short lifespans of insects. Isotope geolocation has shown promise for overcoming these obstacles. Here, I develop and apply metals and metal isotopes, specifically strontium isotope ratios (⁸⁷Sr/⁸⁶Sr), to increase the spatial precision of isotope geolocation and demonstrate how isotopic geolocation tools can advance our understanding of insect migration at the population level. In the first chapter, I test the validity of using ⁸⁷Sr/⁸⁶Sr, lead isotopes, and a suite of 23 metals and metalloids to estimate the natal origins of migratory insects, by investigating the pathways of metal incorporation into butterfly wing tissues. Using an 8-week diet-switching experiment, I show that the concentrations of many metals in insect wings can be altered through the adult diet or dust deposition, making them poor candidates for geolocation but potentially interesting tools to study insect physiology, diet, or toxicology. For example, lead was found to accumulate on butterfly wings from external sources, and lead isotopes could potentially be used to quantify the exposure of migratory insects to metal pollution. Some metals, including Ba, Cs, Mg, Na, Rb, Sr, Ti, Tl, and U, are good candidates for developing geolocation tools. I focused on ⁸⁷Sr/⁸⁶Sr and demonstrated that, despite some caveats, this tool is valid for isotope geolocation. In the second chapter, I outline the steps required to use ⁸⁷Sr/⁸⁶Sr for the geolocation of insects, including the calibration of a spatial model of isotopic variation (i.e., an isoscape) using random forest regression. I then combine hydrogen isotope values (δ²H) and ⁸⁷Sr/⁸⁶Sr into a dual assignment framework to estimate the natal origins of a single generation of monarch butterflies in eastern North America. I demonstrate that combining these two isotopes provides a more spatially constrained estimate of natal origin than using either isotope alone. In the third chapter, I apply this framework to characterize the migratory patterns and migratory connectivity of an insect species across a geographical barrier, the Sahara. Painted ladies journeying northwards across the Sahara appear to do so in a gradual progression, although spatiotemporal sampling limitations prevented a complete characterization of this movement. In contrast, painted ladies migrating southwards appear to journey in a broad front, parallel migration pattern with little longitudinal movement. Evidence for a leapfrog migration pattern was found in the western region, wherein butterflies of northernmost origin journey farther south than butterflies bred in more southerly regions. This leapfrog migration pattern suggests distinct migratory behaviours within painted lady butterflies wherein some individuals migrate longer distances than others. In the fourth chapter, I apply isotope geolocation to characterize the migration distances of multiple individuals and assess the potential genetic differentiation of butterflies migrating distinct distances. I use δ²H and ⁸⁷Sr/⁸⁶Sr-based geographic assignment to confirm that some painted ladies migrate up to 4,000 km from Europe to sub-Saharan Africa, while others migrate shorter distances from Europe to the circum-Mediterranean region. Despite these differences in migration distance, genome-wide analysis revealed a lack of adaptive variation between short- and long-distance migrants. Instead, variation in migration distance in painted lady butterflies is likely the result of a plastic response to environmental conditions. Overall, the methodological developments presented in this thesis are a step forward in studying insect migration. The development and application of metals and metal isotopes for insect geolocation opens new avenues to study the migration phenomenon at different scales with widespread relevance for conservation and pest management.