Time to spread your wings…

March has just started and throughout Australia migratory shorebirds are getting ready to leave for their breeding grounds. Australia is part of the East Asian – Australasian Flyway (EAAF), a migratory route which extends from within the Arctic circle southwards through east and south-east Asia to Australia and New Zealand. Migratory shorebirds spend their non-breeding season, September through to March/April, in Australia and breed in the northern hemisphere from Northern China to Siberia. For a species like the Bar-tailed Godwit that breeds in Alaska this means a return journey of 22,000km every year. Shorebirds do not complete this journey in one flight, but make one or more stops to refuel; the Yellow Sea between China and the Koreas being the principal stop-over area within the EAAF.

Since shorebirds cross many borders during their migration, their conservation is an international issue. Australia is a party to several international conventions and agreements that aim to protect migratory shorebirds (e.g. the China-Australia Migratory Bird Agreement, the Bonn Convention and the Ramsar Convention on Wetlands), but recent population declines suggest that the current legislation is not effective.

Several studies across the EAAF have shown that the majority of shorebird species are in decline (MacKinnon et al. 2012, Ma et al. 2014 and Hansen et al. 2015). Within the Yellow Sea, of the 25 (sub)species with sufficient population data, 24 are declining while only one species is increasing (Conklin et al. 2014). The numbers in Australia are similar with 10 out of the 13 most common migrant species declining in numbers (Rogers et al. 2011). In May 2015, the conservation status of the Eastern Curlew (Numenius madagascariensis; pictured below) and the Curlew Sandpiper (Calidris ferruginea) within Australia was upgraded and they were listed as Critically Endangered under the Environment Protection and Biodiversity Conservation Act 1999. Both species had experienced a population decline greater than 80% in the last three generations (81.4% and 80.8% respectively).

Eastern Curlew (Numenius madagascariensis) – photo credit: Ray Turbull

Recent research has shown that the population declines occur when the birds are away from their non-breeding grounds, with survival rates dropping from around 0.99 in Australia to 0.70 when they are away (Piersma et al. 2015). With benign weather conditions at the breeding grounds the most likely explanation for the decrease in survival is the rapid habitat loss occurring in the Yellow Sea.

Much of the Yellow Sea tidal flats are under threat from land reclamation for agriculture, aquaculture and industrial development. Two developments that are currently under construction are among the largest reclamation projects on earth, Saemangeum in South Korea (40,100ha) and the Caofeidian port in China (31,000ha) (MacKinnon et al. 2012). In most east Asian countries, the cost of land reclamation is far less than the purchase of pre-existing land (MacKinnon et al. 2012). Murray et al. (2014) quantified the loss of tidal flats in the Yellow Sea over the past 50 years and found that of the 1.12 million hectares of tidal flats in existence in the mid-1950’s, only 389,000ha were left in the 2000’s; this equates to a net loss of 65%.

Long term population trends are a vital tool in assessing the effects of habitat loss in the Yellow Sea and can provide early identification of a population in decline and in need of a recovery plan. The Australian Wader Study Group (AWSG) has been carrying out shorebird surveys in north-west Australia for many years. This area was chosen as it supports the largest concentration of migratory shorebirds in the EAAF during the non-breeding season. In 2008, the area was home to 421,000 shorebirds (Rogers et al. 2009). In 2004, the AWSG started the MYSMA (Monitoring Yellow Sea Migrants in Australia) project which consists of three annual shorebird surveys (one in the breeding and two in the non-breeding season) at Roebuck Bay, Bush Point and a 60km stretch of Eighty Mile Beach. Once every seven years the entire coastline between Cape Keraudren in the south and Point Coulomb in the north is surveyed – a stretch of 420km.

Last November, two staff members from Terrestrial Ecosystems, Ray Turnbull and Dr Margot Oorebeek, participated in the full area survey. A team of 18 volunteer and professional shorebird researchers surveyed the entire coastline in six consecutive days. Surveys were conducted around the morning high tides while the birds were roosting on the waterline. Depending on the access to the sites, surveys were conducted by car, quad bike or on foot. Over 400,000 birds were counted of an impressive 43 species. The counts are currently being processed and compared to earlier surveys in 2008 and 2001. These long term comparisons will give a good indication of the health of the EAAF flyway.

For further information on shorebird research in northwest Australia and the EAAF please visit: www.globalflywaynetwork.com.au and www.awsg.org.au.

Thanks to Margot Oorebeek for preparing this post

References

Conklin, J.R., Verkuil, Y.I. and Smith, B.R. (2014). Prioritizing migratory shorebirds for conservation action on the East-Asian Australasian Flyway. WWF-Hong Kong, Hong Kong.

Hansen, B.D., Menkhorst, P., Moloney, P. and Loyn, R.H. (2015). Longterm declines in multiple waterbird species in a tidal embayment, southeast Australia. Austral Ecology, 40: 525–527.

Ma, Z., Melville, D.S., Liu, J., Chen, Y., Yang, H., Ren, W., Zhang, Z., Piersma, T. and Li, B. (2014). Rethinking China’s new great wall. Science, 346: 912–914.

MacKinnon, J., Verkuil, Y.I. and Murray, N. (2012). IUCN situation analysis on east and southeast Asian intertidal habitats, with particular reference to the Yellow Sea (including the Bohai Sea). IUCN, Gland, Switzerland.

Murray, N.J., Clemens, R.S., Phinn, S.R., Possingham, H.P. and Fuller, R.A. (2014). Tracking the rapid loss of tidal wetlands in the Yellow Sea. Frontiers in Ecology and Environment, 12: 267–272.

Piersma, T., Lok, T., Chen, Y., Hassell, C.J., Yang, H-Y., Boyle, A., Slaymaker, M., Chan, Y-C., Melville, D.S., Zhang, Z-W. and Ma, Z. (2015). Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. Journal of Applied Ecology, doi: 10.1111/1365-2664.12582.

Rogers, D., Hassell, C., Oldland, J., Clemens, R., Boyle, A. and Rogers, K. (2009). Monitoring Yellow Sea Migrants in Australia (MYSMA). North-western Australian shorebird surveys and workshops, December 2008.

Rogers, D.I., Hassell, C.J., Boyle, A., Gosbell, K., Minton, C., Rogers, K.G. and Clarke, R.H. (2011). Shorebirds of the Kimberley Coast – Populations, key sites, trends and threats. Journal of the Royal Society of Western Australia, 94: 377–391.

Photo credit: Top – shorebird flock on a beach during the recent MYSMA survey – Margot Oorebeek; bottom – Dr Margot Oorebeek conducting shorebird counts – Ray Turnbull