STATE OF CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF FISH AND WILDLIFE REPORT TO THE FISH AND GAME COMMISSION A STATUS REVIEW OF THE TRICOLORED BLACKBIRD (Agelaius tricolor) IN CALIFORNIA CHARLTON H. BONHAM, DIRECTOR CALIFORNIA DEPARTMENT OF FISH AND WILDLIFE February 2018 Status Review of the Tricolored Blackbird in California California Department of Fish and Wildlife—February 2018 Table of Contents LIST OF FIGURES ............................................................................................................................................ v LIST OF TABLES .............................................................................................................................................. v LIST OF APPENDICES .................................................................................................................................... vi ACKNOWLEDGMENTS ................................................................................................................................. vii EXECUTIVE SUMMARY .................................................................................................................................. 1 REGULATORY FRAMEWORK .......................................................................................................................... 6 Petition Evaluation Process....................................................................................................................... 6 Status Review Overview............................................................................................................................ 6 Existing Regulatory Status ......................................................................................................................... 7 California Endangered Species Act ........................................................................................................ 7 Federal Endangered Species Act ........................................................................................................... 8 California Species of Special Concern and USFWS Birds of Conservation Concern ............................... 8 Migratory Bird Treaty Act ..................................................................................................................... 9 California Fish and Game Code ............................................................................................................. 9 BIOLOGY AND ECOLOGY ............................................................................................................................... 9 Species Description ................................................................................................................................... 9 Taxonomy ................................................................................................................................................ 10 Geographic Range and Distribution ........................................................................................................ 10 Breeding Range ................................................................................................................................... 10 Winter Range ...................................................................................................................................... 12 Distribution of Breeding Colonies ........................................................................................................ 12 Winter Distribution ............................................................................................................................. 14 Genetics and Population Structure ......................................................................................................... 14 Movements ............................................................................................................................................. 16 Itinerant Breeding ............................................................................................................................... 17 Home Range and Territoriality ................................................................................................................ 19 Colonial Breeding and Social Behavior ................................................................................................... 20 Habitat Associations and Use.................................................................................................................. 23 Nesting Substrate ................................................................................................................................ 24 Water .................................................................................................................................................. 27 ii Status Review of the Tricolored Blackbird in California California Department of Fish and Wildlife—February 2018 Foraging Habitat ................................................................................................................................. 28 Diet and Food Habits............................................................................................................................... 30 Reproduction and Survival ...................................................................................................................... 31 Breeding Phenology and Behavior ...................................................................................................... 31 Reproductive Success .......................................................................................................................... 32 Survival ................................................................................................................................................ 36 STATUS AND TRENDS IN CALIFORNIA ......................................................................................................... 36 Range ...................................................................................................................................................... 36 Distribution ............................................................................................................................................. 37 Central Valley ...................................................................................................................................... 38 Southern California and Baja California .............................................................................................. 41 Population Trend .................................................................................................................................... 42 Breeding Population ............................................................................................................................ 42 Colony Size .......................................................................................................................................... 53 Winter Population ............................................................................................................................... 55 Integrated Population Model .............................................................................................................. 58 Regional Shifts in Abundance ................................................................................................................. 58 Central Valley ...................................................................................................................................... 59 Southern California and Baja California .............................................................................................. 60 Northern and Central Coasts ............................................................................................................... 62 EXISTING MANAGEMENT ............................................................................................................................ 62 Land Ownership within the California Range ......................................................................................... 62 Habitat Conservation Plans ..................................................................................................................... 64 Natural Community Conservation Plans ................................................................................................. 68 Conservation Plan for the Tricolored Blackbird ...................................................................................... 71 Protection of Agriculture Colonies from Losses to Harvest .................................................................... 72 Regional Conservation Partnership Program ...................................................................................... 73 Habitat Restoration and Enhancement .................................................................................................. 74 USFWS National Wildlife Refuges ....................................................................................................... 74 NRCS Easements and Incentive Programs .......................................................................................... 74 California Department of Fish and Wildlife Lands .............................................................................. 75 California Environmental Quality Act ..................................................................................................... 76 iii Status Review of