The Western Bristlebird is a medium-sized brown, ground-dwelling songbird with short wings and a long tail. It is 17 cm long and weighs 26–39 g. The crown and hindneck are dark brown with light-brown mottling. The sides of the neck are light brownish-grey with faint scalloping which merge into light-brown ear-coverts. The eyebrow is pale grey while the chin and throat are off-white with fine dark-brown scalloping. The upperbody is all dark brown, with the mantle, scapulars and upper back mottled pale grey, and the lower back and rump having a rufous tinge. The uppertail is olive brown with rufous edges. The breast is light brownish-grey with dark-brown scalloping and the belly is off-white, grading to brown on the flanks, with fine dark-brown scalloping. The undertail is brownish grey. The wings are rufous brown above and brownish grey below. The bill is dark grey with a pale base to the lower mandible, the eyes are red-brown and the legs and feet are greyish. The sexes are alike. Juveniles are similar to adults, but lack mottling and scalloping on their plumage. The Western Bristlebird usually occurs in pairs, but has also been observed singly or in small family groups.
Western Bristlebird |
Status: Endangered on the EPBC Act list
Government evidence of impact of climate change:
Australian Government, Conservation Advice, Dasyornis longirostris
Climate change is an emerging threat due to increased temperature; reduced rainfall and increased storm intensity which are likely to increase the threat of fire.
Over time; the threat from bushfires is likely to increase for western bristlebirds; as fire intensity and frequency are predicted to increase in their primary habitat as a result of climate change (Bradstock 2010 Garnett et al. 2013).
It is projected with high confidence that climate change will result in a harsher fire weather climate in south west Western Australia (CSIRO BoM 2017).
A warmer; dryer climate is expected to result in increased storm intensity and a greater incidence of lightning caused bushfires.
Climate change Increased suspected It is projected that climate change will result in average temperature future temperatures continuing to rise across all seasons; and and reduced reduced winter and spring rainfall in south west Western rainfall Australia (CSIRO BoM 2017).
The species flies weakly and reluctantly; only flying low over short distances (DPaW 2014); making it susceptible to several threatening processes including fire and predation.
Lindenmayer et al. (2009) stated it is likely that; in the absence of predator control; the rate of predation increased where vegetation cover had been removed by fire; which may have an important effect on population recovery after fire events.
At Two Peoples Bay Nature Reserve; moist heaths were reoccupied 2 3 years after a fire event (Burbidge 2003).
The species was found in heaths 5 years after fire between Boulder Hill and east of Waychinicup River; and 14 28 years after fire in northern Fitzgerald River National Park (McNee 1986).
Threats The primary threat to the western bristlebird is increasing fire frequency and intensity (Garnett et al. 2011 DPaW 2014); which is likely to be compounded by increased predation following intense fire events.
Threat factor Threat type Evidence base and status Fire Increased fire known Western bristlebirds are fire sensitive due to their preference frequency present for long unburnt habitat and sedentary nature.
Given the low and intensity population size; fire events are the most significant threat to the persistence of the species (DPaW 2014) and extensive fire is likely to be the cause of historical range contraction (BirdLife International 2016).
Fire is known to lead to increased predation for cover dependent species.
It is inferred from studies on eastern bristlebird that the western bristlebird is likely to be highly susceptible to predation after fire due to loss of dense protective cover; a greater number of individuals in small refuge areas to which feral predators have increased access (Lindenmayer et al. 2009 OEH 2012).
Prescribed burning practices could also have a deleterious impact on the western bristlebird.
These potential impacts derive from issues including seasonality of burning (i.e. during breeding); removal of key forage support (i.e. seeding species) and the increase in total fire frequency.
However; as fire is the primary threat to this species; and a large fire has the capacity to burn several of the identified sites in a single event; the western bristlebird only occurs at three locations (Two Peoples Bay Nature Reserve area; Mount Manypeaks Nature Reserve area and Fitzgerald River National Park area) (K Atkins pers. comm. 2017).
The western bristlebird population is continuing to decline due to ongoing loss of area; extent and quality of habitat due to increased incidence and extent of fire throughout the western bristlebird range (A Burbidge pers. comm. 2017).