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Beluga whales are year-round residents of the Arctic and top predators in the ecosystem. Many beluga whale populations are migratory and spend winters in polynyas and breaks in the ice to avoid entrapment. Once the ice in begins to break up and melt, beluga whale populations migrate to the same Arctic estuaries year after year. Possible uses of estuaries include feeding, aiding in skin sloughing, protection of calves from predators, and other warm water benefits. However, much is still unknown about the use of these habitats both spatially and ecologically. I investigated estuary use by Cumberland Sound beluga whales, through their distribution. Their summering area covers northern fiords of Cumberland Sound, including Clearwater Fiord where there is a large estuary. While the whales are known the frequent the fiords, the specific distribution and core areas were unknown. Using very high resolution satellite imagery, I established critical habitat within the summering region. I also provided an updated estuary abundance estimate for this small beluga whale population. Second, I explored estuary use of Hudson Bay beluga whales by investigating the primary feeding season. Migratory species often have one season where they eat the majority of their food for the year and build fat reserves, which provides energy and supports thermoregulation. This fat can be used to investigate feeding ecology of whales. Despite being the largest beluga population, fundamental ecological knowledge of Hudson Bay beluga whales, such as the primary feeding season is unknown. I used lipid content and adipocyte size throughout the blubber of Hudson Bay beluga whales to identify when they were consuming the majority of their food. I determined that there was no consistent primary feeding season, and therefore both summering and wintering areas were used for feeding. By exploring the beluga whales’ use of seasonal habitat through distribution and foraging ecology, my thesis illuminates fundame

Predators are widely recognized for their irreplaceable roles in influencing the abundance and traits of lower trophic levels. Yet, predators also shape community interactions and ecological processes via localized pathways, irrespective of their influence on prey density or behavior. I synthesized empirical and theoretical research and identified pathways by which predators have indirect ecological effects confined to discrete patches. This synthesis revealed how predators indirectly affect other species via patches – ranging from mediating scavenger interactions to influencing parasite/disease transmission risk – and ultimately provides a more holistic view of predation in ecosystems. I then demonstrated how satellite imagery could resolve whether Arctic foxes create biogeochemical hotspots via their denning behavior. Using satellite imagery, I showed that Arctic fox dens have greater plant productivity and green-up faster than reference sites, supporting the hypothesis that Arctic foxes cause the unique vegetation on their dens by concentrating nutrients derived from prey remains there. I then assessed how predators influence the reproductive ecology of Canada geese. Birds presumably select nest sites in areas they perceive are safer, but few links between spatial patterns of risk and nest habitat selection or nesting success exist. By comparing habitat selection models fit to goose nest locations and fox movement locations, I showed predator activity strongly affects the spatial distribution and reproductive success of geese. However, these effects were mediated by the date nest incubation started, revealing how nesting phenology and predator activity interact to shape bird reproduction. Finally, I assessed how fox predation affects goose reproductive success from an ecosystem-level perspective. I showed winter environmental conditions influence the abundance and availability of main winter foods for Arctic foxes, which in turn showed a numerical response to the

The loss and degradation of freshwater habitats in Canada threaten the rich array of plant and animal species supported within these ecosystems, threatening the biodiversity that these ecosystems sustain. Assessing the distribution of the species in these threatened ecosystems is necessary for the effective monitoring of the well-being of their populations and the ecosystem, but it can be difficult, as some species can evade traditional survey methods due to their elusiveness, size, range, or rarity. Environmental DNA (eDNA), which describes the pool of DNA present in an environment that can be collected in and isolated from environmental samples, offers an alternative to traditional surveying that can be more sensitive and less invasive. Therefore, I developed and validated TaqMan™ MGB probe-based eDNA assays for six freshwater fishes of conservation concern in Manitoba: Bigmouth Buffalo Ictiobus cyprinellus, Chestnut Lamprey Ichthyomyzon castaneus, Golden Redhorse Moxostoma erythrurum, Hornyhead Chub Nocomis biguttatus, Northern Brook Lamprey Ichthyomyzon fossor, and Silver Lamprey Ichthyomyzon unicuspis. The designed assays were validated in situ using paired eDNA and capture-based sampling and used to map the distribution of the above species from water samples collected and filtered from 129 sites across Manitoba in 2021–2023. I detected the eDNA of four of the target species outside of their historic range: Bigmouth Buffalo in the Roseau, Morris, and Assiniboine rivers; Golden Redhorse in Hazel Creek; Hornyhead Chub in waterbodies of the Winnipeg River watershed where it has not been reported previously; and Northern Brook Lamprey in Boggy River. Apart from Northern Brook Lamprey, the eDNA of all target species was not detected in at least one site within their historic range. Further research is needed to confirm if the lack of eDNA detections of the target species within their historic range is a result of range restriction, or if a refinement of the methods

Arctic terrestrial ecosystems are some of the most extreme environments on earth, with a polar climate and landscapes recently carved by glacial retreat. Soil nutrient availability is a limiting factor for tundra productivity and under these conditions, the impacts of consumer-driven nutrient cycling can be magnified. Arctic foxes (Vulpes lagopus) are predators that act as ecosystem engineers in arctic and alpine tundra heath by altering the environment of their den sites, which exhibit increased soil nutrients, verdant atypical vegetation, and deeper snow. These fox dens are biogeochemical hotspots in otherwise nutrient-limited ecosystems and sources of cascading effects across trophic levels. It has been long hypothesized that these dens are so biotically productive because Arctic foxes increase the deposition rate of limiting nutrients by concentrating prey-derived nitrogen (N) and phosphorus (P) in the soil and this hypothesis has been descriptively supported but, the mechanism had not been confirmed with experimentation. To test the ability of the nutrients concentrated by Arctic foxes to cause the ecosystem effects observed on fox dens, I examined a long-term field experiment in Wapusk National Park. Vegetation plots received N and P additions (estimated from fox activity) and/or snow fencing on the windward side to increase snow depth. I investigated how the species composition of plot plant communities changed over 5 years, the treatment effects on plant productivity, intraspecific changes in prostrate shrub leaf metabolism, the response of resident insect communities, and the space use by collared lemmings. I found that nutrient addition facilitates the invasion of tall grass that can accumulate deep snow cover in the winter, deep snow can magnify some effects of increased nutrients, and the nutrient/snow combination can shape plant communities and create preferred lemming habitat. My thesis demonstrates how N and P deposition, increased to a rate within th

Knowledge of species habitat requirements, movements, and life cycles is important for understanding their ecology and functions in ecosystems, and is critical for enabling their effective conservation and monitoring, particularly in small-island states where conservation resources are limited. Island biogeography and ecological release theories make broadly supported predictions about the evolution of generalist traits among small-island birds in the Caribbean, and this research examines the influence of small-island conditions on the life cycle adaptations, diets, and distribution of birds and their responses to human land-use such as agriculture to inform conservation research and management. Using mist-netting, I found that 10 common terrestrial bird species on Grenada (3 endemic to the East Caribbean) exhibited similar patterns of low breeding period seasonality, followed by synchronized peaks in moult intensity and uncommonly high rates of moult-breeding overlap during peak rainfall and high arthropod abundance, despite the wide range in size, morphology, and phylogeny of these species. I studied patterns of seasonal diet composition and diet-overlap among species using DNA meta-barcoding of feces, which suggested that moult-breeding overlap may result from restricted time periods over which arthropod availability is sufficient for breeding and moult to occur. Diet analyses also indicated that agricultural habitats provide important year-round food sources. Lastly, repeated point-count surveys indicated increased bird diversity and abundance at high elevations and in closed-canopy habitats during the dry season, while many birds moved to low elevations and open-canopy habitats in the wet season. Much of Grenada consists of a diverse mosaic of closed-canopy secondary forest patches, interspersed among more open agroforests and small-scale cropping and grazed areas. These agroecosystems appear to provide important habitats and foods to birds throughout the year

Migration poses significant challenges for organisms, especially those traveling long distances. It is hypothesized that despite these challenges, migration evolved as a method of resource maximization and competition reduction. Along with morphological adaptations, species often develop life history traits in complement with their migratory habits. Urbanization and artificial light have further complicated migration patterns for many species. This thesis was aimed at addressing gaps in our understanding of the life history of the Eastern Whip-poor-will (Antrostomus vociferus) in relation to their migratory behaviour and to determine the impact of artificial light on their migratory routes. I captured whip-poor-wills at their breeding locations in southern Manitoba and north-western Ontario and used direct-tracking technologies (archival GPS units; radio telemetry tags) to collect data on timing, routes, and return rates. I used the resulting migration tracks and Bayesian generalized linear models to test for an effect of artificial light levels on route tortuosity along fall migratory pathways. I found that whip-poor-wills took more indirect flight paths on nights when a direct path would result in exposure to more intense artificial light, suggesting they sacrifice efficiency for light avoidance. Next, I used 6 years of capture data, a displacement experiment, and automated radio-telemetry to quantify recapture rates and site-fidelity at breeding territories. I found evidence for high survival rates and site fidelity: annual recapture rates ranged from 50 – 80% and average recapture of birds on the same territory in subsequent years was 75%, 75% of birds returned after displacement, and 90% of radio-tagged birds survived to be detected by receiver towers along the spring migratory routes in the year following tagging birds. Since whip-poor-wills have a longer than average life span and lower annual clutch sizes for a small migratory land bird, my results showing h