The foraging ecology of Caspian Terns (Hydroprogne caspia) on Peel-Harvey Estuary, south-western Australia. Submitted by Susie Stockwell This Thesis is presented for the degree of Bachelor of Science Honours School of Veterinary and Life Sciences, Murdoch University, 2019 Declaration I declare that this Thesis is my own account of my research and contains as its main content work, which has not previously been submitted for a degree at any tertiary education institution. Susie Jill Stockwell Acknowledgements I am filled with gratitude for the baalap (people), boodja (places) and kaadadjan (knowledge), as well as the beautiful birds themselves, which have been integral to the success of this project. Firstly, to my incredible supervisors, Professor Neil Loneragan, Dr. Nic Dunlop and Claire Greenwell, thank you for your support, your time and your generosity in sharing ideas, advice, and opportunities throughout the project. Your passion for ecological sciences and conservation has been inspiring, and I am so grateful for your encouragement, understanding, and support throughout our Caspian project. Thank you especially to Claire Greenwell, my fellow ‘ternologist,’ you have been an academic inspiration and such an amazing friend, I am so grateful for your love and support and our birdy adventures throughout the project. I have been overwhelmed with gratitude for the community support for the Caspian Tern project, in particular to Bob Patterson, Dave Martin, and Jesse Steele. Your passion for the birdlife of Peel-Harvey Estuary, and your knowledge, friendship, and photographic contributions have been invaluable throughout the field season. Thank you also to Dr. Peter Coulson, Dr. James Tweedley, Katherine Stockwell, and Kate Born, for your time and enthusiasm with the otolith, PRIMER and GIS components of the project. To my wonderful family, friends, and all who have been part of my journey from the central Kimberley to the south-west coast and everywhere in between. I am thankful for your love, support, and friendship. I am also grateful and acknowledge the Wadjuk-Noongar people as Traditional Custodians of Peel-Harvey Estuary, and pay respects to all Elders past and present. Finally, I would like to express my gratitude for all who invest their hearts and minds in the love and conservation of our natural world, not only on the Peel-Harvey but across the world. Sir David Attenborough is famously quoted, saying: "No one will protect what they don't care about, and no one will care about what they have never experienced." While I’ve always believed this to be the case, this project has reminded me time again of the beauty of nature and the power of humanity in contributing towards its protection. 2 Abstract Terns and noddies (subfamily Sterninae), comprising almost 15% of all seabird species, are largely piscivorous predators found from temperate to tropical regions in both coastal and pelagic systems. The largest species, the Caspian Tern (Hydroprogne caspia) has a cosmopolitan distribution, but despite this they are largely understudied, especially the finer- scale patterns of their distribution, abundance and foraging ecology throughout non-breeding periods. In south-western Australia, most H. caspia populations are restricted to two or three pairs, except for a large group of approximately 120 birds that breed annually on Penguin Island, Shoalwater Bay. This study investigated the foraging ecology of H. caspia over the first five months of their non-breeding season, from October 2018 to February 2019 on the Ramsar- listed Peel-Harvey Estuary. A single overnight roosting site for H. caspia was identified on the Estuary where a maximum of 147 birds were recorded in mid-February 2019. Tern foraging activity was concentrated at six main areas across the estuary, although tern counts and foraging activity varied between these areas, and foraging activity also differed significantly with time of day throughout the study period – it was greatest in the morning block. Overall, H. caspia were recorded taking 17 prey species (16 fish and one crustacean) on the Estuary, the most common being whitings (Sillaginidae), mullets (Mugilidae) and Eight-lined Trumpeter (Pelates octolineatus), comprising 35.0%, 33.9% and 14.4% respectively of their observed catch. The results of this study highlight the significance of the Peel-Harvey Estuary for the conservation of H. caspia in south-western Australia and the connectivity between the birds on the Estuary in the non-breeding period and those on Penguin Island during the breeding season. In addition, H. caspia appear to be strong candidates as biological indicators of Estuary health. The results of this study provide a basis for an ongoing monitoring plan to contribute towards the conservation and management of the birds and the environment at this Ramsar-listed site. 3 Table of Contents Declaration ..................................................................................................................... 2 Acknowledgements ........................................................................................................ 2 Abstract .......................................................................................................................... 3 Table of Contents ........................................................................................................... 4 Chapter 1. General introduction ..................................................................................... 6 1.1 Foraging ecology of seabirds ........................................................................................................ 7 1.2 Caspian Terns (Hydroprogne caspia) ........................................................................................... 8 1.3. Seabirds as indicators of ecosystem health ................................................................................ 12 1.4. Study aims and research questions ............................................................................................. 14 Chapter 2. Literature review: the foraging ecology and energetic requirements of seabirds with a focus on the larger terns .................................................................................... 15 Summary ........................................................................................................................................... 15 2.1. Introduction ................................................................................................................................ 16 2.1.1 Larger terns .......................................................................................................................... 17 2.1.2 Aims of the review ............................................................................................................... 19 2.2. Foraging ecology of larger terns ................................................................................................ 21 2.2.1 Foraging area ....................................................................................................................... 22 2.2.2 Diet ....................................................................................................................................... 27 2.2.3 Foraging behaviour .............................................................................................................. 28 2.3. Energetic requirements .............................................................................................................. 31 2.3.1 Estimating field metabolic rates ........................................................................................... 32 2.3.2 Energetic requirements of terns ........................................................................................... 33 2.4. The significance of understanding foraging ecology ................................................................. 34 2.4.1 Seabird conservation ............................................................................................................ 34 2.4.2 Seabirds as biological indicators .......................................................................................... 36 2.5. Knowledge gap .......................................................................................................................... 36 2.6. Conclusion ................................................................................................................................. 37 Chapter 3. Patterns of distribution, abundance and foraging ecology of Caspian Terns (Hydroprogne caspia) on the Peel-Harvey Estuary, south-western Australia. ............ 39 Summary ........................................................................................................................................... 39 3.1. Introduction ................................................................................................................................ 40 3.1.1. Seabird foraging ecology .................................................................................................... 40 3.1.2. Caspian Terns in south-western Australia........................................................................... 41 3.2. Methods...................................................................................................................................... 45 3.2.1 Study area ............................................................................................................................. 45 4 3.2.2 Tern