So much is unknown about Queensland Bush Stone-curlew ecology and behaviour. Information for this article has been gathered from publicly available sources and research undertaken by Griffith University PhD student, Scott O’Keeffe, who is mid-way through a project on urban Bush Stone-curlew ecology.
The Bush Stone-curlew or Bush Thick-knee (Burhinus grallarius) is a large ground- dwelling bird with a wingspan of 55-60 cm. They can live for 20 years, sometimes more. They are a terrestrial predator adapted to stalking and running. Bush Stone-curlews are considered common in Queensland but since no monitoring of the species has been carried out in South East Queensland, it is possible that they could suffer the serious declines evident in southern states. In New South Wales they are listed as Endangered and in Victoria, Threatened.
The Bush Stone-curlew call is an evocative and unforgettable sound. It is a penetrating, strident, wail, rising with a slight waver, and dropping at the end and often repeated a number of times in quick succession.
Bush Stone-curlews inhabit open country and avoid dense vegetation. Their ancestral habitats include grasslands, open woodland, mallee, mangroves and rainforest fringes. They are also found in highly modified environments such as golf courses, rail reserves, roadsides with sparse vegetation, urban parkland and grazing land. Curlews prefer landscapes that give them good visibility at ground level, so they usually inhabit areas with bare ground or low ground cover and widely spaced trees and shrubs. Sites where the ground is covered with leaves, twigs, sticks, stones or sparse grass are preferred for nesting since curlews rely on camouflaged eggs and cryptic plumage to avoid predators.
Curlews protect themselves by combining natural camouflage with good visibility to see predators approaching. If necessary they can respond with distraction and threat displays called ‘mantling’. Animals that take eggs and chicks include the usual suspects such as foxes, dogs and cats (feral and pet). Native predators include kookaburras, goannas, pythons, quolls and the Australian White Ibis.
Since curlews are largely nocturnal, they roost inconspicuously during the day in clumps of trees or among fallen timbers. In urban areas, curlews will often roost in raised garden beds with clumped shrubs and grasses or grass-like plants. Curlews forage at night in open areas such as playing fields, parkland, pasture with low grass, and sometimes mangroves, salt marshes and mudflats. The home ranges of curlews appear to vary widely according to ‘habitat quality’ and food abundance.
Bush Stone-curlews are mainly nocturnal and specialise in hunting small grassland animals, mainly invertebrates. They will also take some small vertebrates such as frogs, lizards, snakes and occasionally small mammals. In coastal areas, they may add molluscs and crustaceans to their diet. Curlews will also eat small seeds and fruits. They obtain moisture from their food and do not need surface water for drinking.
The range of unusual behaviours exhibited by many curlews in urban areas suggests that they are capable of significantly modifying their behaviour to take advantage of urban resources.
For instance, curlews breed in Brisbane’s Southbank Parklands, despite the constant presence of noisy humans and traffic. During the day they roost quietly in the edges of shrubbery unnoticed by the crowds. At night, they can often be seen in the shopping precinct harvesting the bounty of insects and geckoes that are drawn to bright lights.
Bush Stone-curlews are masters of camouflage, which they use to hide themselves, their nests and their young from potential predators. An adult curlew on a nest. Photo by Todd Burrows.
Curlew eggs. Photo by Todd Burrows.
In some instances, curlews have adapted to nesting in concrete environments, next to walls and buildings, and even in seemingly hostile environments such as industrial estates with little vegetation. They have been observed nesting under buildings including a demountable site office on stumps in an industrial estate. Curlews in the wild have no equivalent nesting sites. Curlews have been observed collecting cigarette butts and surrounded their nests with them. Perhaps the nicotine in the cigarette butts repels parasites or acts as an insecticide.
Curlews…are capable of significantly modifying their behaviour to take advantage of urban resources.
How Adaptable are Curlews?
Consider the case of Coochiemudlo Island. Between 2001 and 2014, the human population rose by 47%, from 518 to 759. In that same period, the curlew population increased by 154%, from 74 to 188 birds. Over this time, the island has seen significant growth in housing, changes to the natural environment and the introduction of more pet cats and dogs. As more people have settled on the island, they have thinned the island’s natural forest cover, creating a park-like environment, increasing the potential foraging areas for curlews. Unlike the mainland, there are fewer fences restricting curlew movement and there are no foxes.
A significant proportion of residents deliberately provide food for the curlews, which may be significant enough to increase fitness and therefore survival of chicks and adults. This is not a firm conclusion, and the role of supplementary feeding is still under investigation.
Sedentary or Migratory?
Studies in NSW and Queensland have recorded short distance flights by curlews (up to about 15 km) as well as long distance movement (500 km over two nights). But we have no clear picture of patterns of, or triggers for, movement through the landscape. Do we need to provide continuous terrestrial habitat corridors for movement, or can curlews successfully negotiate the city to move from one physically isolated patch to another? We just don’t know.
Curlews nesting under a building in Oxley. This behaviour shows one way in which curlews have adapted to urban areas. Photo by Scott O’Keeffe.
A fox takes a Bush Stone-curlew egg from a nest near Ipswich.
Our knowledge of the ecology of Bush Stone-curlews remains limited. However, we can still propose some practical measures, based on sound science and observation, to assist with their conservation:
• Minimise disturbance of curlew nesting areas by restricting human and pet access, such as leashing your dog while walking in a park.
• Do not approach nesting curlews, especially with a dog.
• Do not place food near curlew nests (well-meaning but ill-advised). Even the residual smell of food can attract animals, including predators which can kill curlews and their chicks.
• Assess an area before undertaking gardening or maintenance. Curlews
on their nests and their eggs are well camouflaged and can be easily overlooked by gardeners. Avoid working within ten metres of a curlew nest.
• Fence woodland remnants that are known or potential curlew habitat areas, and leave fallen branches and debris on the ground.
• Use wildlife-friendly fencing that allows curlews to move and spot predators.
• Report sightings of pest animals and assist local government to manage wild dogs, feral cats and foxes.
• Manage domestic and feral animals on your own property.
• Carefully manage introduced weed species to enhance curlew habitat. Areas where dense, tall grasses grow are avoided by curlews.
• Join patches of native vegetation to increase the size of habitat areas and avoid clearing native vegetation.
To share your sightings of Bush Stone- curlews in the Greater Brisbane area or to find out more about Scott’s research, contact Scott O’Keeffe c/ Environmental Futures Research Institute, Griffith University or 0457 328 442 or [email protected].
A wide wing display is one way in which Bush Stone-curlews try to distract potential predators away from their nests. Photo by Scott O’Keeffe.
References & Further Reading
Department of Environment and Conservation NSW (2006) NSW Recovery Plan for the Bush Stone-curlew Burhinus grallarius. DEC, Sydney.
Pizzey G & Knight F (2012) The Field Guide to the Birds of Australia. Harper Collins.
Sleigh S, Williams L & Stothers K (2010) The Bush Stone-curlew in Northern Victoria – Conversations and Conservation. Goulburn Broken Catchment Management Authority.
Threatened Species Network. Australian Threatened Species: Bush stone-curlew Fact Sheet.
Article co-authored by Amanda Maggs, Brisbane City Council and Scott O’Keeffe, Griffith University.