Predicting condor range expansion in California to reduce development threats

2020 Summer.Includes bibliographical references.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

Applying circuit theory and landscape linkage maps to reintroduction planning for California Condors.

Conservation practitioners are increasingly looking to species translocations as a tool to recover imperiled taxa. Quantitative predictions of where animals are likely to move when released into new areas would allow managers to better address the social, institutional, and ecological dimensions of conservation translocations. Using >5 million California condor (Gymnogyps californianus) occurrence locations from 75 individuals, we developed and tested circuit-based models to predict condor movement away from release sites. We found that circuit-based models of electrical current were well calibrated to the distribution of condor movement data in southern and central California (continuous Boyce Index = 0.86 and 0.98, respectively). Model calibration was improved in southern California when additional nodes were added to the circuit to account for nesting and feeding areas, where condor movement densities were higher (continuous Boyce Index = 0.95). Circuit-based projections of electrical current around a proposed release site in northern California comported with the condor's historical distribution and revealed that, initially, condor movements would likely be most concentrated in northwestern California and southwest Oregon. Landscape linkage maps, which incorporate information on landscape resistance, complement circuit-based models and aid in the identification of specific avenues for population connectivity or areas where movement between populations may be constrained. We found landscape linkages in the Coast Range and the Sierra Nevada provided the most connectivity to a proposed reintroduction site in northern California. Our methods are applicable to conservation translocations for other species and are flexible, allowing researchers to develop multiple competing hypotheses when there are uncertainties about landscape or social attractants, or uncertainties in the landscape conductance surface