PRE-TRANSLOCATION ASSESSMENT OF LAYSAN ISLAND, NORTH-WESTERN HAWAIIAN ISLANDS, AS SUITABLE HABITAT FOR THE NIHOA MILLERBIRD (ACROCEPHALUS FAMILIARIS KINGI) by Mark MacDonald BSc. Forestry & Environmental Management A Thesis, Dissertation, or Report Submitted in Partial Fulfillment of the Requirements for the Degree of MSc. Forestry in the Graduate Academic Unit of Forestry Supervisor: Tony Diamond, PhD, Faculty of Forestry & Environmental Management, Department of Biology. Graham Forbes, PhD, Faculty of Forestry & Environmental Management, Department of Biology. Examining Board: (name, degree, department/field), Chair (name, degree, department/field) This thesis, dissertation or report is accepted by the Dean of Graduate Studies THE UNIVERSITY OF NEW BRUNSWICK 01, 2012 ©Mark MacDonald, 2012 DEDICATION To the little Nihoa Millerbird whose antics, struggles and loveliness inspired the passion behind this project and have taught me so much about what it means to be a naturalist. ii ABSTRACT The critically endangered Nihoa Millerbird (Acrocephalus familiaris kingi), endemic to Nihoa Island, is threatened due to an extremely restricted range and invasive species. Laysan Island once supported the sub-species, Laysan Millerbird (Acrocephalus familiaris familiaris), before introduced rabbits caused their extirpation. A translocation of the Nihoa Millerbird from Nihoa Island to Laysan Island would serve two goals; establish a satellite population of a critically endangered species and restore the ecological role played by an insectivore passerine on Laysan Island. Laysan Island was assessed as a suitable translocation site for the Nihoa Millerbird with a focus placed on dietary requirements. This study showed that Laysan Island would serve as a suitable translocation site for the Nihoa Millerbird with adequate densities of invertebrate prey. Additionally, a discriminant function that allows for in-field sexing of Nihoa Millerbirds was developed and provides an indispensable tool for managers of this species. iii ACKNOWLEDGEMENTS I would like to thank my field assistants, Daniel Tsukayama and Elise Christenson, for their tireless work collecting the invertebrate samples on Nihoa Island and Laysan Island. Holly Freifeld, Cindy Rehkemper, and Beth Flint at USFWS, Pacific Remotes office for all their assistance getting this project off the ground and facilitating its execution. Shiela Conant for her dedication to the Nihoa Millerbird and her kind words for my research. Lab mates, Leeann Haggerty and Julie Henderson for their support and advice over the years. Lastly, a huge thank you to co-supervisors Dr. Graham Forbes and Dr. Tony Diamond for their endless patience and encouragement. iv TABLE OF CONTENTS Dedication............................................................................................................................ii Abstract...............................................................................................................................iii Acknowledgments..............................................................................................................iv Table of Contents.................................................................................................................v List of Tables.....................................................................................................................vii List of Figures ..................................................................................................................viii Chapter 1 - Introduction ...................................................................................................... 1 Previous Research ............................................................................................................... 4 Research Objectives ............................................................................................................ 6 Thesis Format...................................................................................................................... 7 Literature Cited ................................................................................................................... 8 Chapter 2: Comparison of invertebrate availability to Nihoa Millerbirds (Acrocephalus familiaris kingi) on Nihoa and Laysan Islands…………………………………………..14 Introduction ....................................................................................................................... 14 Methods............................................................................................................................. 16 Results ............................................................................................................................... 22 Inter-island Comparisons .............................................................................................. 22 Within-island Comparisons .......................................................................................... 22 Conclusions and Conservation Implications ..................................................................... 25 Literature Cited ................................................................................................................. 27 Chapter 3: Behavioural and Morphological Sex Determination of Nihoa Millerbirds (Acrocephalus familiaris familiaris)……………………………………………………. 34 Introduction ....................................................................................................................... 34 Methods............................................................................................................................. 36 Behavioural Sexing ....................................................................................................... 36 Morphological Sexing ................................................................................................... 37 Genetic Sexing .............................................................................................................. 39 Statistical Analysis ........................................................................................................ 40 Results ............................................................................................................................... 41 Behavioural Sexing ....................................................................................................... 41 Morphological Sexing ................................................................................................... 42 v Discriminant Function Analysis ................................................................................... 43 Discussion & Conclusions ................................................................................................ 44 Literature Cited ................................................................................................................. 46 Chapter 4: Conclusion…………....................................................................……………54 Future Areas of Research...................................................................................................55 Habitat Use......................................................................................................................56 Breeding Biology.............................................................................................................56 Monitoring.......................................................................................................................57 Literature Cited..................................................................................................................58 Curriculum Vitae...............................................................................................................59 vi LIST OF TABLES Table 1-1. Comparison of variables influencing Nihoa Millerbird survival between Laysan and Nihoa Islands. ................................................................................................ 10 Table 1-2. Nesting habits of Acrocephalus warblers (adapted from Bocheński and Kuśnierczyk 2003). ........................................................................................................... 11 Table 1-3. Arthropod parts identified from fecal samples collected from 16 Nihoa Millerbirds on Nihoa Island. Adapted from Morin and Conant 1997. ............................. 12 Table 2-1. Numbers of known Nihoa Millerbird territories in areas of Nihoa Island. ..... 27 Table 2-2. Dominant vegetation among different areas of Nihoa and Laysan Islands. .... 27 Table 2-3. Invertebrate taxa sampled on Nihoa (n = 317) and Laysan Islands. (n = 371)....................................................................................................................................27 Table 2-4. Number of individual invertebrates and weight of invertebrate samples per plot on Nihoa (n = 317) and Laysan (n = 371) Islands. .................................................... 28 Table 2-5. Mean biomass of plots associated with individual vegetation species on Nihoa Island. ................................................................................................................................ 28 Table 2-6. Mean biomass of plots associated with different areas on Nihoa Island ......... 28 Table 2-7. Mean weight of invertebrate samples per plot on Laysan Island. ................... 28 Table 3-1. Comparison of behavioural and genetic sexing for 85 Nihoa Millerbirds sampled in 2007. ..............................................................................................................