THE FORAGING ECOLOGY, HABITAT USE, AND POPULATION DYNAMICS OF THE LAYSAN TEAL (Anas laysanensis) by Michelle H. Reynolds A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biology Virginia Polytechnic Institute and State University Approved by Jeffery R. Walters, Committee chair Curtis Adkisson, Committee member E. F. Benfield, Committee member James Fraser, Committee member William Steiner, Committee member Defense date October 31, 2002 Blacksburg, VA Keywords: Anas laysanensis, foraging ecology, habitat use, population estimate, survival, island waterfowl, Laysan Island THE FORAGING ECOLOGY, HABITAT USE, AND POPULATION DYNAMICS OF THE LAYSAN TEAL (Anas laysanensis) Michelle H. Reynolds ABSTRACT The Laysan teal, an endangered species, is restricted to a single population on Laysan Island, a remote atoll of the Hawaiian archipelago. Little is known of the Laysan teal’s ecology, therefore, I examined food habits, habitat use, and population dynamics. These aspects of its ecology are fundamental to the species management and conservation. I described diel and nocturnal habitat use, home range, and foraging with radio telemetry in 1998-2000. Most individuals showed strong site fidelity during the tracking period, but habitat selection varied between individuals. Mean home range size was 9.78 ha (SE 2.6) using the fixed kernel estimator (95% kernel; 15 birds with >25 locations). Foraging was strongly influenced by time of day: birds spent only 4% of their time foraging in the day, but spent 45% of their time foraging at night. Time activity budgets from the island’s four habitat zones indicated that the coastal zone was rarely used for foraging. The birds foraged 42% of the time they spent in the terrestrial zone at night, but foraged only 4-6% of the time they spent there during other times. Fecal analysis and behavioral observations revealed that the Laysan teal is not a 100% macro- insectivore as previously reported, but consumed seeds, succulent leaves, and algae, in addition to adult diptera, diptera larvae and pupae, ants, lepidoptera, coleoptera, and Artemia. I concluded that this species exhibits high plasticity in foraging behavior. I also studied the parameters influencing the Laysan teal’s population dynamics. Adult survival is high, but duckling survival on Laysan is low, and is a primary demographic parameter limiting population growth. Estimates indicate the population density was high (between 546-827) from 1991 until August 1993, prior to a population crash that occurred between September and December 1993. The most current population estimate (Sept-Nov 2001) is 444 (SE 181) adults. Additional populations (translocation), along with control of non-native mammalian predators, are needed to reduce extinction risks to the Laysan teal. ACKNOWLEDGMENTS This study was funded by U.S. Fish and Wildlife Service’s Ecological Services Pacific Islands Ecoregion, National Geographic Society’s Committee for Research and Exploration, and USGS Pacific Island Ecosystems Research Center. I wish to thank USFWS and NMFS field techs for assistance in the field. Refuge Biologist, Dr. E. Flint, numerous refuge mangers, Karen Rosa (USFWS), and PIERC director Dr. Bill Steiner helped make this research project possible. Cindy Rehkemper, Caroline Mostello, and NOAA provided logistical support. Special thanks to: T. and N. Wilke, P. Bertilsson-Friendman, J. Kelly, M. Veksay, R. Woodward, M. Berry, K. Kozar, P. Banko, A. Marshall for field assistance. K. Kozar, P. Pooler, and G. Ritchotte for assistance with data. USFWS’s E. Flint and C. Rehkemper provided invaluable assistance to coordinate field efforts and data collection. Dr. Thierry Work and Bob Rameyer of USGS National Wildlife Health Research conducted necropsies and stored specimens. I thank my parents for loaning me vehicles, kitchen appliances, and other kindnesses during many visits, passing through to Blacksburg, and through out the ‘re- port’ writing. Mahalo to everyone for sending out letters, books, and edibles to Laysan Island. I thank my graduate advisor, Jeff Walters and committee members C. Adkisson, F. Benfield, J. Fraser, W. Steiner, and statistical advisor Eric Smith for support, guidance, interest, and enthusiasm. iii TABLE OF CONTENTS ABSTRACT.................................................................................................................................I ACKNOWLEDGMENTS .......................................................................................................III CHAPTER 1: THE LIFE HISTORY AND CONSERVATION OF THE LAYSAN TEAL .................................................................................................................................................VIII CHAPTER 1: LIST OF TABLES AND FIGURES...........................................................VIII INTRODUCTION...................................................................................................................... 1 SPECIES DESCRIPTION AND TAXONOMY ..................................................................... 1 DISTRIBUTION AND HABITAT........................................................................................... 3 LAYSAN ISLAND ....................................................................................................................... 3 LISIANSKI ISLAND..................................................................................................................... 4 PREHISTORIC HABITAT .............................................................................................................. 5 GENERAL BIOLOGY AND ECOLOGY .............................................................................. 6 HABITAT USE............................................................................................................................ 6 Foraging .............................................................................................................................. 8 REPRODUCTIVE BIOLOGY ....................................................................................................... 11 Courtship behavior ............................................................................................................ 11 Nesting ............................................................................................................................... 11 Brood Care......................................................................................................................... 13 DEMOGRAPHY......................................................................................................................... 15 Population Size .................................................................................................................. 15 Sex ratio ............................................................................................................................. 15 Mortality and Survival ....................................................................................................... 16 CONSERVATION................................................................................................................... 16 POPULATION AND SPECIES VIABILITY..................................................................................... 16 Demographic and environmental stochasticity ................................................................. 18 Genetic Considerations...................................................................................................... 18 Catastrophes ...................................................................................................................... 19 CURRENT THREATS................................................................................................................. 19 MANAGEMENT RECOMMENDATIONS ......................................................................... 19 TRANSLOCATION .................................................................................................................... 20 Source population .............................................................................................................. 21 Transfer population ........................................................................................................... 21 Selecting and evaluating the release site........................................................................... 21 CAPTIVE PROPAGATION .......................................................................................................... 24 Existing Captive Population .............................................................................................. 24 New captive flocks..............................................................................................................26 CONCLUSION........................................................................................................................... 27 ACKNOWLEDGEMENTS .................................................................................................... 28 LITERATURE CITED ........................................................................................................... 29 iv APPENDICES.......................................................................................................................... 40 CHAPTER 2: THE FORAGING ECOLOGY OF THE LAYSAN TEAL (ANAS LAYSANENSIS) ON A CORAL ATOLL.............................................................................. 44 CHAPTER 2: ABSTRACT....................................................................................................