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.
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
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.
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..
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
For more information about the trials and how you can get involved in monitoring please contact project manager, Chris Purnell.
Suite 2-05, 60 Leicester Street,
Carlton, VIC, 3053