WAMSI 2 - Kimberley Node - 1.2.6 - Evaluating the impacts of local and international pressures on migratory shorebirds in Roebuck Bay and Eighty-Mile Beach

Brief description

The tidal flats of the Kimberley coast support the largest populations of migratory shorebirds in Australia. Eighty Mile Beach and Roebuck Bay are the most important shorebird sites in the region, regularly supporting more than 550,000 migratory shorebirds. Shorebird numbers in north-western Australia have been monitored systematically since 2004, with the long-term objective of developing a dataset that can assess changes in shorebird diversity and numbers over time, and their response to environmental changes, such as local changes in coastal morphology, habitat loss (including that in staging areas), global population decline, climate change and sea-level rise. We seek to extend this monitoring program through the summer of 2012/2013. WAMSI funding was used to carry out two summer shorebird counts, 24-30 Nov 2012 and 9-14 Dec 2012, maintaining the continuity of a 14-year series of systematic counts from Eighty Mile Beach, Roebuck Bay and Bush Point. The data obtained will be added to the existing database, and used in two analyses/publications: (1) An assessment of whether dramatic declines in shorebird abundance in Korea following large-scale reclamation operations resulted in detectable effects in abundance and survival of shorebirds in northwestern Australia; (2) An assessment of whether shorebirds have changed their pattern of high tide roost use since 2004.

Lineage

Statement: The field methodology and statistical approaches to estimate the error associated with shorebird counts in north-western Australia are described in detail in refereed publications (Rogers et al. 2006, Rogers et al. 2011). In brief, one winter survey(June-July) and two summer surveys (Nov-Dec) are carried out each year, in which shorebirds of Roebuck Bay (including Bush Point) and the northern 80km of Eighty-mile Beach are identified to species level and their numbers counted by an experienced team of professional and volunteer shorebird experts. Surveys are carried out at high tide roosts, at times when the tidal flats are submerged and shorebirds are forced into relatively small roosts where it is possible for a team of experienced surveyors to not only identify all species present, but to count all birds of each species. Survey dates and times are carefully selected on the basis of tide predictions to avoid surveying on neap tides (which do not rise high enough to force all birds from the tidal flats), and on spring tides (which can inundate mangrove clearings and salt-pans and provide alternate roost sites for shorebirds that are inaccessible to humans). Shorebird counts over such a large geographical area are based on component counts from many different shorebird roosts. Each component count is entered into the database, enabling an assessment of whether local roost usage changes over time. In the shorebird surveys, all shorebird, gull and tern species are counted. However, in the analysis of the effects of Korean habitat loss on Australian shorebirds, we are likely to focus on one species, the Great Knot Calidris tenuirostris. This is one of the most numerous shorebird species in north-western Australia, and in Korea numbers of Great Knot declined more steeply than any other shorebird species during a major tidal-flat reclamation project (Saemangeum) between 2006 and 2008 (Moores et al. 2008, Moores 2012). It is therefore considered to be the species in which resultant declines in north-western Australia are most likely to be detectable. Changes in Great Knot demography will be compared with that of species which were known to use Korean tidal flats to a lesser extent, most probably Red Knot Calidris canutus and Bar-tailed Godwit Limosa lapponica as colour-banding and age-ratio data (see below) is also available for these species. In addition to using North-western shorebird count data, the analysis of 'Saemageum' effects on Great Knot numbers will include a Mark-recapture analysis of Great Knots, individually colour-banded in north-western Australia by the Global Flyways network since 2005 with intense and systematic resighting effort. The dataset is fully entered, and ready for standard mark-recapture modelling, most probably with Cormack-JollySeber Models as described in (e.g.) Sandercock 2003 and Sandercock (2006). These models estimate apparent annual survival (with associated error) and can be used to assess whether survival has changed over time. We will also examine a data set on age-ratios within cannon-net catches by the Australasian Wader Studies Group, an index of annual breeding success (Minton 2003). Combining the information on changes in shorebird numbers (from counts), in annual survival (from the Mark-recapture analyses) and breeding success (from age-ratio data), we will develop demographic models for selected shorebird species to assess whether populations underwent changes coinciding with the reclamation of Saemangeum, and the extent to which these changes were driven by adult mortality and annual breeding success.