Valuing coastal habitats: predicting high-tide roosts of non-breeding migratory shorebirds from landscape composition
Yuri Zharikov A B and David A. Milton C DA Centre For Wildlife Ecology, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6 Canada.
B Present address: Pacific Rim National Park Reserve, PO Box 280, Ucluelet, BC, V0R 3A0, Canada.
C Queensland Wader Study Group, 336 Prout Road, Burbank, Qld 4156, Australia.
D Corresponding author. Email: david.milton@csiro.au
Emu 109(2) 107-120 https://doi.org/10.1071/MU08017
Submitted: 17 April 2008 Accepted: 21 January 2009 Published: 26 May 2009
Abstract
Conservation of critical habitats for shorebirds (Charadriiformes : Charadrii), usually requires spatially explicit identification of each habitat. Most non-breeding shorebirds depend on two critical habitats: foraging (intertidal flats) and roosting (safe and open supratidal sites). We used published information on use of high-tide roosts by shorebirds to develop models of roost selection (probability of occurrence) and usage (mean abundance) for 12 species of shorebirds spending the non-breeding season in Moreton Bay, in subtropical eastern Australia. Selection of roosts was most strongly affected by the proximity to a large foraging area, field of view and to a lesser extent by composition of the surrounding landscape. Abundance of the most common species, such as Bar-tailed Godwit (Limosa lapponica), Eastern Curlew (Numenius madagascariensis) and Whimbrel (N. phaeopus), depended on distance to the nearest large foraging area or the size of the roost per se. Our results suggest that the shorebird species occurring in a subtropical Australian estuary use two generalised types of roosts: exposed ocean-front roosts typified by supratidal spits and sandbars and patches of claypan–saltmarsh in the upper reaches of the tidal range surrounded by mangroves. The amount of these habitats available in Moreton Bay was examined by visiting unmonitored sites with a predicted high probability of occupancy by two key species, Eastern Curlew and Bar-tailed Godwit. Few of the unmonitored sites currently supported many shorebirds. These data suggest that despite the high demand on coastal land for urban development in Moreton Bay, suitable roosting habitat is still available near their foraging areas.
Additional keywords: Bar-tailed Godwit, conservation, Eastern Curlew, geographic information systems, GIS.
Acknowledgements
We thank the numerous dedicated counters who have surveyed shorebird roosts during the 10 years of the study. We especially thank the QWSG count coordinator, Linda Cross, without whose tireless efforts checking data and organising counters, the program would have failed. YZ was supported by a post-doctoral fellowship from the National Science and Engineering Research Council of Canada and by the Canadian Wildlife Service of the Environment Canada. Initial drafts of the manuscript were greatly improved by comments from Mark Colwell, Jesse Conklin, Lesley Evans Ogden and two anonymous referees.
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