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Browsing by Author "Aubry, Lise, committee member"

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    Determining the impact of harvest and climate change on the demography of black brant (Branta bernicla nigricans)
    (Colorado State University. Libraries, 2024) Blommel, Caroline, author; Koons, David, advisor; Aubry, Lise, committee member; Webb, Colleen, committee member
    As a coastal long-distance migrant, black brant (Branta bernicla nigricans) are vulnerable to climate and land-use change while also facing harvest pressure from sport hunting along the Pacific Coast. To examine impacts of harvest pressure and environmental change on brant survival and reproductive components of fitness, I combined band-recovery data with live recapture and resighting data from 1990 to 2023 for the Tutakoke River breeding colony of brant on the Yukon-Kuskokwim Delta in western Alaska. I fit multiple Bayesian multistate mark-recapture models to these data to estimate temporal changes in cause-specific mortality and breeding probabilities over the last 33 years. Harvest rate increased over time and is significantly impacted by bag limit across sex and age groups. Adult non-harvest mortality has remained stable over the study period but is higher in years of extreme El NiƱo and Aleutian Low Beaufort Sea Anticyclone events. Breeding probability for previous breeders increased over time while breeding probability for previous non-breeders decreased, driven largely by differing responses to spring timing. My work describing brant demographic response to environmental change and harvest provides valuable information on how to manage brant most effectively across their migratory range.
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    Predicting condor range expansion in California to reduce development threats
    (Colorado State University. Libraries, 2020) Punzalan, Arianna, author; Boone, Randall, advisor; Aubry, Lise, committee member; Aldridge, Cameron, committee member; Ransom, Jason, committee member
    Collisions with wind energy infrastructure is a major cause of wildlife mortality worldwide and especially pose threats to bird and bat populations. Avian species that have associations with habitats that generate strong winds are at higher risk of collision with wind turbines. Critically endangered California condors (Gymnogyps californianus) are among species that use areas with high-class winds. As the condor's population growth continues to face challenges, it is imperative that managers working with the California Condor Recovery Program identify and reduce all threats to the species and foster conditions that promote condor recovery. Renewable energy projects, particularly wind energy, pose risks to condors; and new developments within current, documented condor range require planning and consultation with the United States Fish and Wildlife Service. However, industrial-scale wind energy projects in California consider condor flocks in central and southern California separate and statically persisting within their current ranges. This misconception may result in development within condor habitat that is detrimental to range expansion and recovery. In this thesis, I examine factors that influence condor home range sizes, predict where condors are likely to expand their range within identified suitable habitat in California, and assess where the predicted condor range overlaps with areas that generate high-class winds preferred for wind energy development. My first chapter focuses on estimating annual home ranges of condors and identifying factors that influence home range size. Understanding what intrinsic and extrinsic variables influence condor home ranges can inform management planning and aid in predicting condor range expansion. I used location data collected from condors released in central and southern California to estimate annual condor home range area and assessed twenty-one variables related to individual characteristics, management factors, population dynamics, and habitat suitability to identify strong predictors of home range size. I found that age group, time spent in the wild, age of managing agency, maximum slope, maximum NDVI, distance to water, and road density were significant predictors of annual home range area. On average, adult breeding condors had the smallest home range areas and subadult condors had the largest home range areas. Population size did not affect annual home range size of condors; however, home range size increased the longer a managing agency had been releasing condors. My objective of the second chapter was to predict condor range expansion in California and identify where there may be conflict between condors and potential wind energy development. Predicting condor range expansion may inform managers of areas to concentrate efforts and resources for management and outreach, as well as identify areas that should be considered during wind energy development planning stages to reduce risks to condor recovery. I used the results from Chapter 1 and a habitat suitability surface to create a tool in which a user can customize the demographics of condor flocks in California sometime in the future and predict the overlapping home ranges of individuals in the flocks. Users can then export the predicted ranges into a GIS program to consider how the overlapping home ranges may be affected by plans for wind energy development and identify possible alternative sites. I predicted condor range expansion in California under four scenarios: 1) population size and structure stays the same (2019 California population); 2) each flock has 150 individuals with 15 breeding pairs; 3) each flock has a majority of breeding pairs, which maximizes breeding pairs and minimizes sub-adult condors; and 4) each flock has a majority of subadults, which maximizes subadult condors and minimizes breeding pairs. Predicted ranges under different scenarios exhibited high similarity and areas with high-class wind generation overlapped with <10% of predicted condor range under all scenarios. More than 81% of areas with strong winds suitable for energy generation were unaffected by predicted condor range, suggesting there are alternative areas for wind energy development with less risk of conflict with critically endangered California condors.