Migratory shorebird ecology in the Hunter estuary, south-eastern Australia Jennifer Spencer B.Sc. (Hons) (2001), University of Wales, Cardiff (UK) A thesis submitted in total fulfilment of the requirements of the Australian Catholic University for the degree of Doctor of Philosophy School of Arts and Sciences, Faculty of Arts and Sciences, Australian Catholic University, Sydney, New South Wales February 2010 Migratory shorebird ecology in the Hunter estuary DEDICATION I dedicate this thesis to the memory of my father John “A powerful agent is the right word: it lights the reader's way and makes it plain; a close approximation to it will answer, and much travelling is done in a well-enough fashion by its help, but we do not welcome it and applaud it and rejoice in it as we do when the right one blazes out on us.” MARK TWAIN Spencer 2010 i Migratory shorebird ecology in the Hunter estuary STATEMENT OF ORIGINALITY I declare that this dissertation is my own work and has not been submitted in any form, fully or partially for a degree or diploma at any other university or institution of higher (tertiary) education. All information derived from the published and unpublished work of others has been acknowledged in the text and a list of references is provided. Jennifer Spencer, February 2010 Spencer 2010 ii Migratory shorebird ecology in the Hunter estuary ABSTRACT Migratory shorebirds inhabit the shorelines of rivers, wetlands, oceans and lakes, where they need to rest and feed during their non-breeding seasons to prepare for their annual migrations to breeding grounds in the Arctic. Along their flyways many non-breeding and stop-over sites are under pressure from coastal developments, disturbance, global sea level rise and water resource development. In this thesis I investigated how migratory shorebirds responded to habitat loss in the Hunter estuary, a non-breeding site in south-eastern Australia, and how they used remaining estuarine habitats. The Hunter estuary is a wetland of international importance but has a long history of modification from industrial and urban development which began in the late 1800s. Based on recent counts (2001-07), the Hunter estuary now only supports two species in internationally significant numbers (Eastern Curlews Numenius madagascariensis and Sharp-tailed Sandpipers Calidris acuminata) compared to seven species listed from earlier records (1970-90). Overall, I detected a 42% decline in total numbers of migratory shorebirds (1981 - 2007) in the estuary, with significant declines (44 - 83%) in four species. The tidal cycle was the main driver for the distribution of shorebirds in the Hunter estuary with most species feeding in exposed intertidal mudflats at low tide and being forced to rest at high tide. Eastern Curlews roosted on artificial structures and sandbanks during the day but at night they moved to flooded saltmarshes. Shallow water was important at the roost sites, as it provided a mechanism for cooling on warm days and for detecting predators at night. Vigilance behaviour made up 30 - 40% of Eastern Curlews roosting time, but vigilance increased by about 20% prior to their migration (Feb-Mar). Day roosting habitat was most limited during spring high tides and periods of high disturbance. Disturbance was significant at the day roosts (0.8 - 1.7 hr-1), mostly from birds of prey, but Eastern Curlews spent longer in flight after being disturbed by people. The tidal period and tide type (neap or spring) determined shorebird distribution on intertidal mudflats. Intertidal mudflats in Fullerton Cove provided important feeding habitat for many species, but artificial mudflats impounded in the North Arm of the Hunter River extended foraging time for small shorebird species which fed until the tide forced their relocation to the main day roosts. These impoundments increased in importance for all shorebirds during neap cycles and one to three hours before high tide when the availability of intertidal mudflats was limited in the rest of the Hunter estuary. Overall, a high percentage (> 90%) of Bar-tailed Spencer 2010 iii Migratory shorebird ecology in the Hunter estuary Godwits Limosa lapponica foraged during low tides and 50% of godwits continued to forage up to three hours after low tide. Foraging Bar-tailed Godwits were most successful in mudflats in Fullerton Cove but prey availability was not uniform among mudflats. Saltmarshes provided major night roosting habitat and important feeding habitat for small shorebird species, including Sharp-tailed Sandpipers, which foraged in saltmarsh regardless of the tidal period. Generally, most shorebird species avoided saltmarshes with large stands of mangroves, preferring sites with open saltmarsh and tidal pools. Changes in attitudes towards wetlands management in the last three decades coincided with the formal protection and rehabilitation of shorebird habitat in the Hunter estuary. In 1995, culverts were removed to restore tidal flushing to estuarine wetlands on Ash Island, a highly modified wetland complex in the Hunter estuary. Although high inter-annual variability in migratory shorebird populations made it difficult to detect short-term responses to wetland manipulation, long-term monitoring (1994-2007) indicated that increased tidal flushing had promoted mangrove expansion indirectly reducing habitat availability for shorebirds. Mangrove removal has the potential to restore this imbalance, but further studies are needed to support an adaptive management approach to managing shorebird habitat in the Hunter estuary. The cumulative loss and degradation of estuarine habitats in south-eastern Australia and other parts of the East Asian-Australasian flyway continue to threaten shorebird populations, but these impacts could be addressed through greater commitment to the protection and active management of shorebird roosting and feeding habitats in their non-breeding range. Spencer 2010 iv Migratory shorebird ecology in the Hunter estuary ACKNOWLEDGEMENTS Many people made the completion of my thesis possible. Sincere thanks to my supervisors, Neil Saintilan, Richard Kingsford and Vaughan Monamy, for their support and encouragement throughout my project and for their reviews of draft chapters of this thesis. The Australian Catholic University, the University of Newcastle, the Australian Research Council and the Kooragang Wetland Rehabilitation Project (KWRP) (Hunter-Central Rivers Catchment Management Authority) and Energy Australia provided financial and logistical support. I thank Peggy Svoboda, Rob Henderson, Terry Sullivan and Sue Rostas (KWRP) for their support on Ash Island. The Hunter Bird Observers Club shared their enthusiasm for shorebirds and their expertise. My thanks to Ann Lindsey, Terry Lindsey, Liz Crawford and Chris Herbert for their good company in the field and for sharing their knowledge of the Hunter estuary. I am indebted to my other field assistants: Sarah Spencer, Lisa Knowles, Alex Gaweda, Anne Miehs, Tyler Smith, Joel Stibbard, Alice Howe, Allan Richardson and Michelle Foate. Lisa Knowles also assisted with benthic invertebrate identification and data entry. I would also like to thank José Rodríguez, Geoff Macfarlane, Elizabeth Huxtable, Brian Timms, Danny Rogers, Silke Nebel, Yuri Zharikov and Craig Gibson for their encouragement and advice on project design; Pat Hutchings, Roger Springthorpe (Australian Museum) and Joanne Ling for their assistance with benthic invertebrate identification; Alice Howe for her assistance with sediment analysis; Geoff Gordon and Martin Krogh for their statistical advice; and Walter Boles for access to the Australian Museum’s shorebird collection. Count data for the Hunter estuary were supplied by the Hunter Bird Observers Club, the Australasian Wader Study Group, Phil Straw, Clive Minton, Richard Kingsford, and Mick Murphy and Phil Craven from the NSW National Parks and Wildlife Service. My thanks to Alice Howe, Liz Crawford, Chris Herbert, Alan Stuart, Max Carpenter, Kerry Murton and Jane Spencer for their comments on draft chapters; to John Spencer for repairing the outboard motor and providing a boat trailer; the Jervis Bay Marine Park for loaning night vision equipment; and to Max Carpenter and Kerrylee Rogers for their assistance with site figures. I would also like to thank staff and students, past and present, of the School of Arts and Sciences. Lastly, I could not have completed my thesis without the support and patience of my family, friends and Max. Spencer 2010 v Migratory shorebird ecology in the Hunter estuary PUBLICATIONS RELATED TO THIS THESIS . Spencer, J.A. and Kingsford, R. T. (in review). Observer error in shorebird counts. (Appendix A1). Spencer, J. A., Monamy, V., and Breitfuss, M. (2009). Saltmarsh as habitat for birds and other vertebrates. Chapter 7 In ‘Australian Saltmarsh Ecology’. (Ed. N. Saintilan). pp. 149-165. (CSIRO publishing: Collingwood, Victoria). (Appendix A2). Howe, A. J., Rodríguez, J. F., Spencer, J.A., MacFarlane, G.R. and Saintilan, N. (in press). Response of estuarine wetlands to reinstatement of tidal flows. Marine and Freshwater Research. Spencer 2010 vi Migratory shorebird ecology in the Hunter estuary CONTENTS DEDICATION .............................................................................................................................i STATEMENT OF ORIGINALITY .............................................................................................ii ABSTRACT ............................................................................................................................