Eastern Bristlebird
Eastern bristlebird (Dasyornis brachypterus)
Just a little brown bird with a bristly face
The eastern bristlebird is a small ground-dwelling bird approximately 20 cm long with the tail accounting for about one-half of its total length. It may look like just another small, brown bird. Look more closely though and you will see features such as the short wings, strong legs, and distinct bristles in front of the eyes that are perfect adaptations for living amongst dense ground vegetation. The eastern bristlebird lives a secretive life, foraging and nesting in thick ground foliage. Its elusive nature means that you are unlikely to see it, although you may hear it. This plucky little bird uses a distinctive and loud melodic song to mark its territory and warn other eastern bristlebirds to "back off".
The elusive eastern bristlebird. Photo: DERM
Different from the rest
Today, the eastern bristlebird is restricted to three geographically separate areas in eastern Australia. The smallest and most northern occurrence is centred upon the Border Ranges of south-eastern Queensland and adjacent parts of north-east New South Wales. This small group is endangered. Observers have found that the birds in this population are quite different from their southern cousins and may be a sub-species. This makes these few birds stand out from the rest as a very special and distinct group.
Eastern bristlebird feeding and breeding
The eastern bristlebird obtains food mainly from the ground by probing the surface, though they may also glean foliage or snatch flying insects. Food items include insects (e.g. ants, bugs, beetles and orthopterans, seeds, small fruits and earthworms).
Birds are active by day but sedentary, spending the majority of time hidden amongst low dense vegetation. Calling begins after sunrise, often after rain. Like many other birds, eastern bristlebirds do not appear to like cool mornings and are reluctant to call when conditions are unfavourable. Males usually call from on top of a conspicuous ‘calling’ log within their territory. If a female is in the territory, she will often respond, but it can be difficult for the untrained ear to distinguish between the two calls. Throughout the day, both birds keep in contact with short ‘clicks’ known as contact calls.
Breeding pairs establish permanent territories of 1-4 ha with calling birds 100-300 m apart. The breeding season extends from late July to February. During this time a female may produce several clutches of eggs. The number of offspring produced is not known nor is the survival rate of chicks. Time of breeding varies depending on weather, with timing most likely triggered by storms or heavy rain, which stimulate grass growth and insect activity.
A nest is constructed by the female over a few days. It is built just above the ground amongst shelter. After construction, two eggs are laid 24 hrs apart. The eggs are cream coloured with a pinkish tinge and are heavily spotted with brown and purplish brown. Incubation of bristlebird eggs takes approximately 21 days and is performed by the female. The male brings food to the female during incubation.
Eastern bristle eggs. Photos: Grant Fraser
After the eggs hatch, the male undertakes the majority of the feeding of the young. The female does all of the brooding of the chicks. After about 13 days the first feathers begin to erupt from the pin feathers. After another 4 or 5 days, the chicks fledge and are dependant on the male and have very little to do with the female hereafter. If conditions are favourable after the chicks fledge, the female will begin to construct a new nest after about three days. After a further 18 days (36 days after hatching) the chicks are fully independent.
Discovery and loss
Most sightings of the eastern bristlebird in southeast Queensland date from the middle of the last century. A geographically isolated colony in the Conondale Range north of Brisbane wasn’t discovered until the 1980’s.
Small, localised populations appear to be the norm based upon historical accounts and the observations of scientists and birdwatchers. Some colonies were depleted or disappeared completely during the very dry conditions in the early 1990’s which were accompanied by severe wildfires. Severe disturbance especially wildfire is known to have caused localised extinction of birds previously.
The burning issue
The northern population of the eastern bristlebird lives in moist, mountain ranges within about 100 km of the coast. In Queensland most sightings have been within localised pockets of relatively open eucalypt forest in close proximity to denser vegetation along creek lines and rainforest. Soils are relatively fertile, derived from basalts of the Main Range Volcanics and Mt Warning Shield. However, a colony at Mt Barney lives in shrubby montane heath vegetation on poorer soils and a colony once occupied similar habitat near Surprise Rock in Lamington National Park.
The ground stratum of the eucalypt forests favoured by the eastern bristlebird is a mosaic of dense clumped grasses interspersed with patches of shrubs, ferns, tangled vines and fallen logs. The more common grasses include wild sorghum (Sarga leiocladum), kangaroo grass (Themeda triandra) and tussock grass (Poa labillardieri). The presence of mature wild sorghum tussocks is thought to be a good indicator of high quality bristlebird habitat.
Tussocks of wild sorghum. Photo: Rowena Thomas
Planned use of fire seems to be the best way to guarantee that some of the important components of eastern bristlebird habitat, especially tussock grasses, continue to be available in the places where they live. Without fire, dense regeneration of trees and shrubs occurs quickly in the moist conditions and grasses become shaded out. There is also an increased risk of severe wildfire during dry times. Wildfires kill native wildlife and destroy the food and shelter required by survivors over extensive areas. However, deliberate use of fire on a regular basis can also cause changes to the vegetation that do not necessarily benefit the eastern bristlebird. An example is the replacement of preferred grass species by fire tolerant species such as blady grass (Imperata cylindrica). Finding a balance with regards to timing, frequency and extent of fire is crucial to the eastern bristlebird's future as well as for a range of other threatened species that live in similar habitat (e.g. Hasting’s River mouse , and the vine Marsdenia longiloba).
When the going gets tough
Having survived for thousands of years and adapted to dramatic changes in the Australian climate, the eastern bristlebird continues to battle numerous threats.
Imagine being a small, brown ground-dwelling bird, unable to fly great distances with the continual threat of being eaten by introduced predators such as foxes and cats and living in a habitat subject to perpetual change.
The eastern bristlebird has developed effective tactics to survive in its fire-prone environment. During fires, adult birds take refuge in the nearby rainforest, though eggs and nestlings may be destroyed if fire occurs during the breeding season in spring. With their short wings, the eastern bristlebird is unable to fly great distances to find new places to live. If habitat is damaged or destroyed, the birds may not be able to reach nearby areas of suitable habitat not already occupied by other eastern bristlebirds.
Monitoring and recovery
A large group of scientists, rangers, volunteers and land managers has been striving to ensure the eastern bristlebird survives within southeastern Queensland. Why are so many people involved? Some of the reasons are:
- searching for the eastern bristlebird and understanding its behaviour and habitat requirements requires a huge amount of effort because of its elusive nature and the rugged terrain in which it lives;
- eastern bristlebird habitat occurs on national park and adjacent private land;
- it is important to understand the possible reasons for the population declines so that future management practices can be adapted.
Two extensive surveys to monitor known colonies and locations where birds once occurred have been undertaken. Much of this work was carried out by volunteers. A new survey is being undertaken in the spring of 2009 as part of a Caring for Our Country project run by Condamine Alliance NRM in partnership with DERM, Birds Queensland, local government and community groups. The Caring for Our Country project is also supporting pest and weed control, fire management and community education. The survey work is also targeting less accessible patches of suitable habitat that have not been visited previously.
|
Sites where eastern bristlebirds were observed during survey (maximum total number of birds observed over visits) |
Sites where eastern bristlebirds have been present previously but none observed during survey or now thought to be locally extinct |
Surveys 1999-2000 |
6 (9) |
8 |
Surveys 2002 |
4 (13) |
10 |
Within national parks, management of habitat has been receiving close attention through control of predators and pigs, and fire regimes that maintain a mosaic of understoreys including dense swards of tussock grasses.
An eastern bristlebird site showing (1) the understorey prior to a planned burn, (2) soon after the fire and (3) in recovery several months later. Photos: Rowena Thomas
A trial re-introduction of birds to the wild was successfully undertaken in late 2008. Two batches of four birds bred by DERM were released into specially prepared sites at Main Range National Park in Queensland and near the Lion’s Road in far northern New South Wales. The birds were monitored by radio-tracking for several weeks after release with three birds surviving at either site. A bird was also heard calling at the Main Range site several months after release.
Last updated: 03 September 2009