FINAL REPORT Foraging Study Least Terns 2009 No Appendices
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FORAGING STUDY of California Least Terns in San Diego Bay 2009 Prepared for Naval Base Coronado under Cooperative Agreement # N62473-08-2-0027 with Naval Facilities Engineering Command Southwest San Diego, California by Patricia Baird, Ph.D. Kahiltna Research Group Simon Fraser University Centre for Wildlife Ecology Burnaby, B.C. Citation: Baird, Patricia. 2010. Foraging study of California Least Terns in San Diego Bay and Near Ocean Waters, San Diego, California. Unpublished Rept. U.S. NAVFACENGCOM, San Diego Part 1 Foraging Study of California Least Terns in San Diego Bay and Near ocean Waters Appendix I Detailed Methods and Data Sheets Appendix II Banding Data submitted to the U.S. Geological Survey Patricia Baird, Ph.D. Part 2 Analysis of Fecal Samples of California Least Terns Collected on U.S. Navy Least Tern Colonies, San Diego Bay 2008 Appendix III Detailed Methods and Data Sheets Daniel J. Pondella, II, MA, Ph.D. and Jonathan P. Williams, MS. Part 3 Summary and Analysis of Past Fish Collection Data, with Comparison to past Tern Productivity, San Diego Bay Appendix IV Detailed Methods and Data Sheets Daniel J. Pondella, II, MA, Ph.D. and Jonathan P. Williams, MS. Project managed by Friends of Colorado Lagoon 1 Part I FORAGING STUDY of CALIFORNIA LEAST TERNS IN SAN DIEGO BAY AND NEAR OCEAN WATERS SAN DIEGO, CALIFORNIA, 2009 FINAL REPORT Patricia Baird, Ph.D. Kahiltna Research Group Centre for Wildlife Ecology Simon Fraser University 125A-1030 Denman Street Vancouver, B.C. V6G 2M6 Canada Photo: Center for Biological Diversity Citation: Baird, P. 2010. Part 1. Foraging study of California Least Terns in San Diego Bay and Near ocean Waters, San Diego, California, 2009. Unpubl. Rept. U.S. NAVFACENGCOM, San Diego. 91 pp 2 TABLE OF CONTENTS Part 1 Foraging of Least Terns in San Diego Bay 2 List of Tables 3 List of Figures 3 Photograph 5 Abstract/Executive 4 Summary Introduction 8 Goals of Project 8 Methods 12 Results 34 Discussion 63 Summary 73 Literature Cited 74 Acknowledgements 79 Appendix I link Detailed Methods and Data Sheets, Part 1 80 Appendix II link Banding Data submitted to the U.S. Geological 87 Survey, Part 1, Least Tern Foraging Study Part 2 Summary of Goals Analysis of Fecal Samples 2008 88 and Results Appendix III link Detailed Methods and Data Sheets, Part 2 89 Part 3 Summary of Goals Summary and Analysis of Past Fish Collection 90 and Results data with Comparison to Past Tern Productivity Appendix IV link Detailed Methods and Data Sheets, Part 3 91 PART I List of Tables 1. Lengths of fish eaten by adults, displayed by species 60 2. Lengths of fish fed to chicks, displayed by species 60 3. Length categories of dropped fish 2009 62 List of Figures 1. Survey tracklines San Diego Bay and near ocean, 2009 14 2. Types of foraging areas in and around San Diego Bay 16 3. Extent of Channel Habitat in San Diego Bay 17 4. Extent of Dock Habitat in San Diego Bay 18 5. Extent of Inlet Habitat in San Diego Bay 19 3 6. Extent of Mooring Habitat in San Diego Bay 20 7. Extent of Near ocean Habitat in San Diego Bay 21 8. Extent of surveyed Ocean Habitat near San Diego Bay 22 9. Extent of Shoreline Habitat in San Diego Bay 23 10. Pelagic transects off the coast of San Diego, 2009 25 11. Map of U.S. Navy colony sites where we surveyed 29 12. Sub-areas at NABO colony 30 13. Distribution of numbers of birds per foraging flock, San Diego Bay, 2009 34 14. Proportional distribution of habitats, and proportion of feeding flocks in San Diego Bay and the near ocean environment 35 15. All locations of least tern foraging flocks 36 16. Location of Least Tern foraging flocks in North San Diego Bay 37 17. Location of Least Tern foraging flocks in Mid San Diego Bay 38 18. Location of Least Tern foraging flocks in South San Diego Bay 39 19. Location of Least Tern foraging flocks in nearshore San Diego Bay 40 20. Location of foraging flocks during the Egg stage 42 21. Location of foraging flocks during the Chick stage 43 22. Foraging locations during the fledge stage 44 23. Delta Beaches, percent birds with prey returning from foraging areas, Egg stage 2009 46 24. Delta Beaches, percent birds with prey returning from foraging areas, Chick stage 2009 47 25. Delta Beaches, percent birds with prey returning from foraging areas, Fledge Stage 2009 48 26. NABO, percent birds with prey returning from foraging areas, Egg stage 2009 49 27. NABO, percent birds with prey returning from foraging areas, Chick stage 2009 50 28. NABO, percent birds with prey returning from foraging areas, Fledge Stage 2009 51 29. MAT Site, percent birds with fish returning from foraging areas, Egg stage 2009 52 30. MAT Site, percent birds with fish returning from foraging areas, Chick stage 2009 53 31. MAT Site, percent birds with fish returning from foraging areas, Fledge Stage 2009 54 32. Proportions of fish prey eaten by adult Least Terns over chick and fledge stages 2009 57 33. Proportions of fish prey eaten by adult Least Terns over each stage, 2009 57 34. Proportions of fish prey fed to chicks by Least Tern adults, 2009 58 35. Prey consumed by chicks over each stage, chick and fledge, 2009 58 36. Lengths of prey consumed by Least Tern adult and chicks, 2009 59 37. Proportions of dropped fish found on Least Tern colonies 2009 61 4 38. Proportions of dropped fish by breeding stage 61 Photograph 1. Least Tern feeding a chick 31 5 ABSTRACT and EXECUTIVE SUMMARY Part 1 The purpose of the project was to provide the U.S. Navy with an understanding of the foraging activities of the federally endangered California Least Tern ( Sternula antillarum browni ) in and around San Diego Bay in 2009, so that the U.S. Navy could comply with the Endangered Species Act (16 USC 1531 et seq.), the Sikes Act Improvement Act (16 USC 670 et seq.), and the Migratory Bird Treaty Act (16 USC 1361 et seq.) in their agreements with the US Fish and Wildlife Service, including the formal endangered species consultation on the Fiddler’s Cove Marine Repairs and Improvements Project at Naval Amphibious Base Coronado (FWS-SDG-4032.6) and the MOU between USFWS and the U.S. Navy Concerning Conservation of the endangered California Least Tern in San Diego Bay. Both the consultation and the MOU recommended further study of the Least Tern foraging behavior around San Diego Bay and the near ocean waters. This research project also fulfills the research goals set forth in the San Diego Bay Integrated Natural Resources Management Plan . We found that California Least Terns foraged most frequently in and around San Diego Bay in 2009, in the following areas. 1) in inlets and mooring areas and along shorelines near their colonies in San Diego Bay, 2) within 400 m offshore in the Pacific Ocean beyond the breakers adjacent to their colonies, 3) offshore up to 24 km in upwelling areas along Nine Mile Escarpment and Colorado Canyon. Terns used these different areas in different frequencies throughout the three breeding stages, egg, chick, and fledge, and foraged nearest the colonies during the chick stage. Major prey for both chicks and adults were silversides (silverside smelt-Atherinops spp. ) and anchovy ( Anchoa spp. ), and also included kelpfish (most likely Giant Kelpfish, Heterostichus rostratus ) for adults. Silversides and anchovy were the same prey consumed in the 1990s, but kelpfish were new to their diet in 2009. All fish were of Age Class 0, young of the year, for both chicks and adults, which corresponds with what Pondella (2008) found in his study on fecal samples from 2008, and what Baird et al. (1997) found in the 1990s in both bill loads and concurrent fecal samples. Adults consumed larger prey than did chicks, and dropped fish were different in proportions of prey type and size than were fish known to be consumed by Least Terns, verifying work done in the 1990s in San Diego and Camp Pendleton. Prey types consumed by Least Terns also did not correspond with the large variety of potential fish prey caught in San Diego Bay, although terns are known to consume some of the same genera of fish caught in fishing gear. 6 This is the first time that regular pelagic foraging, as far as 24 nautical miles from the coast, has been documented for Least Terns, via systematic surveys. Preferred foraging areas in San Diego Bay and the nearshore area were consistent with where they had foraged in the 1990s. Conclusions from this report are limited, because they are based on only one year of data collection, and in a year where there was heavy predation on eggs and chicks. Because of these limitations, the specific questions posed in the goals could not be answered definitively and completely. This study should be considered a baseline study for Least Tern foraging in San Diego Bay and other ocean areas for the early part of the 21 st century. If continued studies are conducted, they will be a good contrast to studies from the 1990s, the methods of which were used in 2009 in this study. Part 2 Part 2 is written by personnel from Occidental College, Vantuna Research Laboratory, who were subcontractors to Kahiltna Research Group (Dan Pondella, Jonathan Williams). Part 2 identifies fish species from otoliths found in fecal pellets of Least Terns on U.S. Navy colonies, from collections in the year prior to this foraging study.