PREDICTING NONRESIDENT SEABIRD FORAGING HABITAT TO INFORM CONSERVATION PLANNING A Thesis submitted to the faculty of San Francisco State University In partial fulfillment of 45 the requirements for the Degree 3 0 2 0(0 Master of Arts &EDG, .s\s In Geography by Anna Justine Studwell San Francisco, California May 2016 Copyright by Anna Justine Studwell 2016 CERTIFICATION OF APPROVAL I certify that I have read Predicting Nonresident Seabird Foraging Habitat to Inform Conservation Planning by Anna Justine Studwell, and that in my opinion this work meets the criteria for approving a thesis submitted in partial fulfillment of the requirement for the degree Master of Arts in Geography and Environment at San Francisco State University. Ellen Hines, Ph.D. Professor of Geography & Environment Barbara Holzman, Professor of Geograffhy & Environment I c e , Jaime Jahncke, Ph.D. Point Blue Conservation Science PREDICTING NONRESIDENT SEABIRD FORAGING HABITAT TO INFORM CONSERVATION PLANNING Anna Justine Studwell San Francisco, California 2016 Seabirds are considered indicators of marine health and food web dynamics, making them sentinel organisms that can alert humans to changes in the marine environment. With increasing human access to the ocean, it is important to understand the risk of disturbance that maritime activities pose to seabirds to support decision-makers in prioritizing areas for elevated management. This research focuses on pelagic, non-locally breeding seabird species in the Greater Farallones National Marine Sanctuary and Cordell Bank National Marine Sanctuaries. A hypothesis was that high-use foraging areas for pelagic seabirds would be influenced by oceanographic and bathymetric factors and that spatial and temporal distributions are similar within planktivorous and piscivorous foraging guilds but differ between them. With data collected by the Applied California Current Ecosystem Studies (ACCESS) partnership, species distribution models were generated to identify high-use foraging areas of six pelagic seabird species. Model results highlighted the continental shelf break, particularly the vicinity of Cordell Bank, as highest use areas. With the exception of one species, there were no significant differences between distributions of individual seabird species within a foraging guild or between guilds. Risk of disturbance to seabirds was assessed using a habitat risk assessment (HRA) model from the inVEST suite of tools. To target seabird foraging that conflicted least with human activities, a conservation prioritization tool, Marxan, was used with seabird foraging area representing the conservation feature of interest and risk derived from the HRA model representing cost. If human activities were not considered in the prioritization, prioritized areas were parts of the continental shelf break and the vicinity of Cordell Bank. If human activities were considered, prioritized areas were to the west of the continental shelf break, in the vicinity and to the northeast of Cordell Bank, and in the vicinity of pre-existing marine protected areas. This research shows that the continental shelf break hosts critical areas for seabirds and provides methods that can be implemented elsewhere to prioritize critical habitat for elevated management as human development pressures continue to expand to the ocean. T n^rtifv that thp Ahctrart io a ™rrect representation of the content of this thesis. ACKNOWLEDGEMENTS I would like to thank my family and friends who have listened appreciatively and embraced my fixation with seabirds; I am lucky to have you and am incredibly grateful for your thoughtful discussions and support. I would also like to thank my committee, Ellen Hines, Barbara Holzman, and Jaime Jahncke who have pushed me to look for creative solutions when a task was challenging. I would like to thank the many partners and contributors who have helped make this research a reality. This thesis was supported by the Applied California Current Ecosystem Studies (ACCESS) partnership, a continuing collaboration between Point Blue Conservation Science, the Greater Farallones National Marine Sanctuary, and Cordell Bank National Marine Sanctuary. I would like to acknowledge the Council on Ocean Affairs, Science, and Technology (COAST), San Francisco State University Robert Maxwell and University Scholarships, and the Romberg Tiburon Center Bay Scholarship and Student Association for their support. TABLE OF CONTENTS List of Tables............................................................................................. vii List of Figures....................................................................................................................... viii Chapter 1 Abstract......................................................................................................................................1 Introduction...............................................................................................................................2 Methods..................................................................................................................................... 7 Study A rea.......................................................... 7 Data Collection & Processing....................................................................................10 Species Distribution Modeling................................................................................. 17 Covariate Selection.................................................................................................... 19 Model Validation & Interpretation...........................................................................21 Habitat Prioritization..................................................................................................22 Seabird Distribution Visualization & Interpretation................................................23 Results..................................................................................................................................... 26 Oceanographic Associations..................................................................................... 28 Bathymetric & Distance-Related Associations........................................................32 Climatic Index Associations .......... 33 Species & Guild Distribution Differences............................................................... 35 Detection Error........................................................................................................... 42 Habitat Prioritization..................................................................................................43 vi Discussion............................................................................................................................... 44 Model Interpretation..................................................................................................45 Conservation Prioritization....................................................................................... 50 Conclusion............................................................................................................... 52 Chapter 2 Abstract............................................................................ 54 Introduction............................................................................................................................. 55 Methods................................................................................................................................... 59 Study A rea..................................................................................................................59 Human Use Spatial Data........................................................................................... 61 Disturbance Rank Data................................. 62 Pelagic Seabird Data..................................................................................................64 Marxan Parameters....................................................................................................65 Results..................................................................................................................................... 73 Risk of Disturbance....................................................................................................73 Disturbance Rankings................................................................................................75 Risk............................................................................................................................. 79 Habitat Prioritization..................................................................................................82 Discussion............................................................................................................................... 85 Conclusion......................................................................................................................... 91 References............................................................................................................................... 92 vii LIST OF TABLES Table Page 1. Table 1.1 Environmental Variables..............................................................11 2. Table 1.2 Seabird Descriptions..................................................................... 19 3. Table 1.3 Seabird Model Results................................................................. 27 4. Table 1.4. Species Distribution Differences................................................42