Floating Roost Trial

 
Eastern Curlew00000004DRW.JPG

Why float?

Desperate birds take desperate measures on high tides

Throughout the East Asian Australasian Flyway, roosting sites for migratory shorebirds are being impacted by coastal development, disturbance and sea-level rise, drastically reducing their fitness, their ability to migrate successfully and ultimately produce young. Artificial roosting sites can be created to help shorebirds in areas which where roost sites are limited.

To date, the construction of artificial shorebird roosts has involved significant earthworks and hydrological alteration to create permanent, static structures. These interventions are successful in creating suitable shorebird habitat but can come at significant costs, have undesired effects on surrounding habitats and are subject to rapid degradation, particularly in intertidal habitats.

Floating roost sites, whether natural or artificial, may form preferential high-tide roost sites for a number of reasons. They are generally consistent throughout the tide cycle and immune to climate change induced sea-level rise. In addition, they are resistant to terrestrial predators and vegetation colonisation and can be relocated on, or adjacent to tidal feeding areas.

Red-necked Stints roost on a floating island of seagrass wrack in the Spencer Gulf

The Trial

BirdLife Australia are excited to announce a trial of artificial roosts modeled on floating, long-line oyster bags (LLOB) as a cheap, low-impact and adaptable alternative to traditional artificial roost construction for shorebirds.

Developed in Australia by local oyster growers LLOB have several benefits over traditional “rack and rail” infrastructure:

  • higher oyster yield & increases oyster growth rate

  • Reduced set up and ongoing labour cost

  • lower impact on local ecological condition of coastal areas

  • Great for waterbirds!!

Waterbirds roost and feed on oyster farms throughout Australia.Why reinvent the wheel?

 
 

A temporary refuge

 
oyster-bag2.jpg

Floating roosts rise a fall with the tide. Either sitting in shallow water or on the tidal flat at low tide and providing an option for roosting on high tides when other natural roosts may be submerged or inappropriate (e.g. too hot, disturbed, vegetated).

 
 

The objectives of the floating roost trials are:

• To test shorebird and waterbird responses associated with LLOB artificial floating roosts.

• To document additional implications of LLOB on intertidal and subtidal ecology.

• To investigate alternate materials for possible use as artificial floating roosts including incorporation of traditional crafts.

This project is contributing to objectives identified in the National Migratory Shorebird Conservation Action Plan (MS CAP) and the Australian Government’s Wildlife Conservation Plan for Migratory Shorebirds.

 
 

Trial sites

The floating roost trial will deploy 1,080 LLOB in coastal habitats across three sites throughout the East Asian Australasian Flyway. Trial roosts will be set up on the South East coast of Australia, and one in the Yellow Sea, Republic of Korea. We will be assessing the use of these roosts by birds, as well as the effects they have on the local ecology and microclimate.

If successful, floating roost sites may be deployed in degraded and threatened internationally significant shorebird habitat throughout the flyway..

 
 
white square 80 percent.png

Western Port Philip Bay

Melbourne Water’s Western Treatment Plant, and adjacent coast have been long renowned as a significant habitat for shorebirds and waterbirds (Rogers et al 2013).

The Port Philip Bay (western shoreline) Ramsar site is recognised for supporting very large numbers of waterbirds, on both its natural and artificial wetlands, with annual numbers likely to be in excess of 300,000.

The area also supports 12 threatened fauna species and is an important drought refuge for waterbirds when inland lakes and wetlands dry out.

 
white square 80 percent.png

Hunter Estuary

The Hunter estuary is considered one of the most important coastal estuaries in New South Wales and supports an abundance and diversity of bird life.

The site supports 112 species of waterbirds and 45 species of migratory birds including internationally significant numbers of Critically Endangered Eastern Curlew.

 
white square 80 percent.png

Geum Estuary

The Geum Estuary and adjacent Janghang coast are recognised as the most important site on the Korean Peninsula for migratory waterbirds (Bamford et al 2009, Jaensch 2013, Moores 2016).

Twenty of the 39 shorebirds species regularly occurring at the Geum Estuary have been recorded in internationally important numbers including critically endangered Spoon-billed Sandpiper, Nordman’s Greenshank and Easterrn Curlew.

image floating roost - new trial.png

Impact.

INTERTIDAL ECOLOGY

Marine and intertidal environments are very sensitive to change. To assess change and mitigate any detrimental impacts the roosts may have on local ecology we have engaged independent consultants to monitor in and around the “bag field” of our roosts throughout the trial.

Marine debri and microplastics

BirdLife and project partners have closely considered potential contributions the roosts may make to marine debri and microplastics.

The initial trial is a proof of concept using commercially available equipment. The roosts are moored to marine grade screw anchors and attached to a super strong poly aqua storm line which is constructed of UV treated polyester displaying advanced hydroscopic properties with breaking strain 435 kg/ft-300mm. The bags are made of High Density Polyethylene (HDPE) and Linear Low Density Polyethylene (LLDPE) which make them both flexible yet strong and UV resistant.

Any plastics left in the ocean run the risk of potential small abrasions… but as plastics go these are the best! The bags are being constantly monitored, although with commercial oyster operations of this type capable of withstanding large Canadian swells, we don’t anticipate bags coming loose in our comparatively calm trial sites. Roost sites deployed in Korea will be unclipped and stored onshore during typhoon season.

Part of the trial is also investigating non-plastic alternatives including bioplastics and traditional Korean materials and handicrafts (kelp and reeds based), which would also be a source of income to coastal communities

20140405_0461.jpg

Contact Us

For more information about the trials and how you can get involved in monitoring please contact project manager, Chris Purnell.

IMG_20190417_121329.jpg
Name *
Name

BirdLife Australia

Suite 2-05, 60 Leicester Street,

Carlton, VIC, 3053