What is an eastern curlew?
Here in Australia, many people are familiar with the bush-stone curlew (Burhinus grallarius). Their eerie cries have been haunting campers nationwide for many years. However, another species of curlew – the eastern curlew (Numenius madagascariensis) – is significantly less well-known and is facing the threat of extinction.
Eastern curlews are the largest wader bird in Australia. They have a very distinctive beak which is long and curves downwards, making them easy to spot. The birds can be seen stalking slowly through sand/mudflats and wetland areas, foraging for food (crustaceans, small molluscs, as well as some insects) from the surface or probing deep in the sand or mud with their long bills.
However, perhaps the most interesting thing that sets the eastern curlew apart from the bush-stone curlew is its massive migration. This species flies all the way from northern China and Russia, through Asia across the Pacific Ocean to Australia, and sometimes even further, to New Zealand, often flying days without a break. A single eastern curlew can fly more than 20,000 kilometres, meaning that if an individual did so for 20 years, it will have flown a distance roughly equivalent to the distance between the Earth and the Moon
If they were to fly only 13,000km, this would also be the equivalent of an 80kg human, running 16 MILLION kilometres almost non-stop and losing 32kg, twice a year.
Why do we need to care?
Eastern curlews are listed under the Environment Protection and Biodiversity Conservation Act 1999 as "Critically Endangered", and have seen declines of up to 80% of their global population in the past 30 years.
Unlike many birds, the eastern curlew can't glide. This means that for stretches of its journey to breeding grounds in the north, the eastern curlew flaps continuously for days on end, not stopping for food or rest. After thousands of kilometres of flying, the eastern curlew loses 40% to 70% of its body weight, and its muscles begin to be digested for energy. Once in Australia, the bird must stop at a feeding ground to rebuild muscle and fat – this is called ‘roosting’. In order to continue the migration north for the following breeding season, the shorebirds need to greatly increase their body weight by feasting during these roosting stopovers. If they don’t build up enough body fat/energy, the birds may die on the next leg of their migration.
Unfortunately, many of the roosting areas throughout Asia and Australia have been heavily impacted by coastal development. Roosting grounds, including coastal wetlands and muddy intertidal zones, have been destroyed, leading to a massive decline in the number of eastern curlews, as well as other shorebirds.
About 75% of the world’s curlews winter in Australia, so we have a particular responsibility to protect them to the best of our ability.
The effect of disturbance
We know it is important that all migratory shorebirds put on as much weight as they can while they’re roosting. However, human disturbance has been identified as one of the major threats to shorebirds at many of the high tide roosting areas in the Mackay region which are in proximity to urban areas
The effect of this disturbance reduces the amount of resting time the birds have, forcing them to use excessive energy at a time when they need to maximise their reserves for migration. This can cause their migration to fail or reduce their ability to breed at the end of migration.
Other threats include:
- Habitat destruction
- Pollution
- Changes to water regimes
- Climate change
- Hunting
- Reclamation of tidal flats
The Eastern Curlew Project
Research has consistently highlighted the importance of high-quality non-breeding habitats to migratory shorebirds like the eastern curlew. Therefore, understanding the habitat use and distribution of individuals across a landscape along with the influences of human disturbance is fundamental to conserving this threatened species.
The purpose of the project, led by Reef Catchments in 2022/2023, was to collate historical monitoring data into a visual habitat prioritisation asset that overlays identified eastern curlew roost sites with mapping of human disturbance in the Mackay region.
So, what does that look like? Keep reading!
The GIS-based Multi-Criteria Decision Analysis (MCDA) is a modelling approach used to facilitate the consideration of multiple, often conflicting, criteria by decision-makers. MCDA transforms and combines geographical data and value-judgements to solve spatial problems. We created the visual habitat prioritisation asset by overlaying historical monitoring data of Eastern Curlew roost sites collected by the Queensland Wader Study Group (QWSG) with key human disturbance layers (parks, dog beaches, walking tracks etc.) for our region.
The above map provides a look at the end product - the impact that humans are having on certain eastern curlew roosting sites within the Mackay region.
Using this mapping product, we can now direct strategic and targeted conservation efforts at highly-impacted sites to help remedy the influence that humans have on roosting shorebirds like the eastern curlew. Keep an eye out for our Eastern Curlew Prospectus releasing soon, which details projects to help conserve these beautiful birds.
The next element of the project entailed pest animal control, for which we decided to use a conservation detection dog. Site selection was based heavily on the mapping product produced above.
Meet Rocky
Rocky is an English Springer Spaniel, who works as a conservation detection dog to help our native species by sniffing out some of the threats that our shorebirds face.
Rocky's job is to track the scent of identified pest animals. In our project, Rocky was looking for Foxes (Vulpes vulpes) to help reduce the pressure that these invasive species pose on shorebirds like the eastern curlew. Rocky is particularly beneficial when species are hard to find, or may be at low densities spread across large areas.
Rocky is equipped with a GPS collar so that all tracks can be recorded, which helps to facilitate appropriate, targeted control of the pest species. Good boy Rocky!
Below is an example of Rocky working. The yellow lines on the map represent the exact search tracks that Rocky took, while the red triangle shows where Rocky found an active fox den. To the south of the site are multiple eastern curlew sites, which, could have easily been heavily impacted by having an active fox den in proximity. Without Rocky's hard work, these dens are often overlooked.
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This project received grant funding from the Australian Governments Environment Restoration Fund.