ResearchOnline@JCU This file is part of the following work: Miller, Mark (2018) Foraging niche specialisation and resource use in tropical seabirds: implications for management. PhD thesis, James Cook University. Access to this file is available from: https://doi.org/10.25903/5b5e4cf5655f8 Copyright © 2018 Mark Miller. The author has certified to JCU that they have made a reasonable effort to gain permission and acknowledge the owner of any third party copyright material included in this document. If you believe that this is not the case, please email [email protected] Foraging niche specialisation and resource use in tropical seabirds: implications for management Thesis submitted by Mark Miller BSc.(Hons), MSc. for the degree of Doctor of Philosophy in the College of Science and Engineering James Cook University Acknowledgements During this project I have had the privilege of getting to know a group of truly awe-inspiring animals. This research has allowed me, and hopefully the reader, the opportunity to understand and admire their lives on a deeper level. Firstly, I would like to thank my supervisor Brad Congdon who allowed me the freedom to find my own path while keeping me on the tracks. Your ability to make me ask the right questions of my garbled and excited ideas has undoubtedly improved the way I think, and your depth of knowledge and linguistic skills are truly inspiring - if I've absorbed any of them then I am certainly a better scientist for it. A huge thanks also goes to my secondary supervisor Nicholas Carlile. Your enthusiasm for seabirds, and drive for doing conservation science the right way are a huge motivation. I am forever indebted to you for saving my first field season with your uncanny ability to extract shearwater chicks from what I was convinced was just tussock! Thanks also to Gabriel Machovsky-Capuska whose hard-working ethic and keen eye for detail pushed me to deliver my best results in the crucial writing stages. Thanks to all my friends and fieldworkers throughout the years. Firstly, to Fiona 'Magnum' McDuie for showing me how the Aussies 'cone' a shearwater and grapple a booby – it has been a joy to follow in your footsteps. Thanks to Mia Derhe, Julia Gulka, Egoitz Alkorta and Steve Ryan for assistance in the field, it was a privilege to share all-night burrow checking and explosive regurgitations in your company. Thanks to Queensland Parks and Wildlife for having me along on their island trips, in particular Damon Shearer, Andrew Dunstan and Graham Hemson. Thanks also to staff and friends on Lord Howe Island: Hank Bower, Christo Haselden, Ian Hutton, Jenn Lavers, Jon Jon, Macca and Fitzy – you have a wonderful island! Thanks to the staff at JCU, particularly Leanne Shillitoe for patience with my admin and travel, and Jen Whan and Chris Wurster for assistance with my stable isotope samples. Also huge thanks to the staff at CSIRO Atherton for letting me join the gang and get involved in their fantastic research. Thanks to all my friends and family for encouragement and putting up with my PhD dramas. In Australia: Karel and Yoska, James and Amy, Kate and Pat, Ryan and Shane. And back in the UK: Mum and Stuart, Matt and Laura, Rosie, Jake, Grace, Georges, Joan, Mib and Chris. Finally, my heartfelt thanks goes to my wife Mia. Your love and belief in me has lightened this journey, and it has been a joy to have shared so much of it with you – here's to the next adventure. I Statement of the contribution of others Contribution type Specific contribution Contributor name/details Dr Bradley C. Congdon, James Cook University, Cairns, QLD Supervision Advisors Mr Nicholas Carlile, Office of Heritage and Environment, Hurstville, NSW Dr Bradley C. Congdon, James Cook University, Cairns, QLD – whole thesis Analytical Dr Gabriel E. Machovsky-Capuska, assistance University of Sydney, Sydney, NSW – Ch. 4 Ms Fabiola R. O. Silva, University of Sydney, Sydney, NSW – Ch. 4 Dr Bradley C. Congdon, James Cook University, Cairns, QLD – whole thesis Mr Nicholas Carlile, Office of Heritage and Environment, Hurstville, NSW – whole thesis Intellectual Dr Fiona McDuie, San Jose State University, Editorial support Moss Landing, US – Ch. 3 assistance Dr Joe Scutt Phillips University of Sydney, Sydney, NSW – Ch. 3 Dr Gabriel E. Machovsky-Capuska, University of Sydney, Sydney, NSW – Ch. 4 Ms Fabiola R. O. Silva, University of Sydney, Sydney, NSW – Ch. 4 Dr Inna Senina, SEAPODYM Collecte Localisation Satellites, Ramonville, data provision FR – Ch. 3 National Environmental Research Program (NERP) Holdsworth Wildlife Research Endowment Lord Howe Island Board research subsidy Grants Stuart Leslie Bird Research Award Financial Birdlife Australia conference travel award support Second World Seabird Conference travel award James Cook University Postgraduate Stipend Research Scholarship (JCUPRS) James Cook University ethics approval Animal ethics A1992 Permits and Australian Bird and Bat Banding Scheme authorization Bird banding license 3125 II Queensland Parks and Wildlife Service (QPWS) Permit WITK08379410 NSW Office of Environment and Heritage Fieldwork Scientific License SL101316 Lord Howe Island Research Board Permit LHIB 03/14 Dr Bradley C. Congdon, James Cook University, Cairns, QLD Mr Nicholas Carlile, Office of Heritage and Environment, Field Data collection Hurstville, NSW assistance Dr Mia A. Derhe, Lancaster University, Lancaster, UK Ms Julia Gulka, University of Manitoba, Vermont, US III ABSTRACT Seabirds are a group of wide-ranging species with complex life histories, and an entirely marine foraging niche. Intra-species niche specialisation in seabirds appears widespread with different populations, sexes and age groups specialising in different marine resources. Seabirds in the tropics are understudied relative to those at higher latitudes. Knowledge gaps in tropical seabird foraging ecology lead to uncertainty about the prevalence of niche specialisation in tropical seabirds. Filling these gaps not only advances our understanding of how tropical seabirds use marine resources but also has important conservation management implications. This study uses regional eastern Australia to investigate three aspects of tropical seabird foraging ecology thought to drive intra-species foraging niche specialisation. The applied ecological findings of each investigation are then translated into direct management actions aimed at safeguarding the regional marine resources of the study populations and tropical seabirds in general. Firstly, multiple years of data on foraging patterns, habitat and resource use in Wedge-tailed Shearwaters Ardenna pacifica breeding on a tropical and sub-tropical colony were used to investigate local adaptation of foraging strategy. Consistent dual-foraging was observed over three years in the tropical shearwater population, whereas the sub-tropical population switched from unimodal to dual-foraging and then back again. Chicks from the tropical population were consistently provisioned with local resources from southern Great Barrier Reef waters whereas adults self-provisioned on resources obtained in the central Coral Sea. The sub-tropical population used local resources in the northern Tasman Sea to sustain chicks. This local resource was shared by adults under unimodal foraging, but under dual-foraging self-provisioning adults shifted to exploit the same Coral Sea resources as tropical conspecifics. As such, chicks and adults have differently specialised foraging niches at the tropical colony but frequently shared the same foraging niche at the sub-tropical colony. Both populations showed a degree of flexibility in their foraging strategy that is related to the long-term reliability of local resources, and used persistent and reliable at-distance resources in the central Coral Sea to buffer local resource depletion. IV Secondly, Wedge-tailed shearwaters from the same tropical and sub-tropical populations were used to investigate the importance facilitated foraging with tuna. Shearwater foraging behaviour was assessed relative to oceanographic covariates and predicted distributions for multiple tropical tuna species and age- classes, simulated by an existing ecosystem model (SEAPODYM). Shearwaters from both colonies undertook long-trips to deep, pelagic waters close to seamounts and foraged most often at fronts and eddies. At broad-scales, shearwaters consistently foraged in areas with higher predicted adult skipjack and micronektonic tuna densities and avoided adult Bigeye Tuna. At finer-scales, dynamic ocean features aggregated tuna of all sizes. Enhanced tuna density at these locations increased the likelihood of shearwater foraging activity. Long-trips in the tropics targeted oligotrophic waters with higher tuna densities. Long-trips in the subtropics targeted enhanced primary productivity, but in some years shifted to target the same oligotrophic, tuna-dense waters used by tropical conspecifics. As such, the foraging niche of the tropical population is consistently specialised on facilitated foraging, whereas the foraging niche of the subtropical population becomes specialised on facilitated foraging in years of low marine productivity. Finally, GPS tracking, dietary and nutritional analysis was used to investigate sex-specific foraging in a tropical Brown Booby Sula leucogaster population. Sex-specific segregation was observed in: a) foraging location: females undertook longer trips, foraging at more distant locations than males; b) foraging time: male activity