(Data from Birds Australia 2010) Northern Population
The northern population habitat occurs in south-eastern Queensland and north-eastern NSW, from Conondale Range (Sunshine Coast Qld) south to the Tweed Range (northern NSW) (see Holmes 1982, 1989 and 1997).
This population has been surveyed intensively in the last 25 years (e.g. Holmes 1989, 1992, 1997, 2001; Lamb et al. 1993; Stewart 1997, 1998; Sandpiper Ecological Surveys 1999, 2000b, 2002, 2003, 2005a, 2005b, 2006a, 2008, 2010, 2012; J. Young unpublished data). The largest number of birds known to have occurred in the northern population is 154 found during a survey in 1988 (Holmes 1989). Garnett and Crowley (2000) estimated that the northern population had declined by approximately 80% during the previous 30 years, and at that time several previously known populations had not been recorded for many years.
The northern population has now decreased to fewer than 40 individuals (see Table 1). Surveys in 2009, 2010 and 2012 failed to visually locate any birds in Queensland (Whitby 2009; D. Stewart pers. comm. 2012), although two unconfirmed calls were detected in 2010 and two calls were recorded in the Lamington Plateau area in 2012. Experts believe that up to 10 birds may still be present in Queensland habitat mainly on private land (D Rohweder and S. Gillman pers. comm. 2010; D. Stewart pers. comm. 2012). Habitat mapping undertaken by the Department of Environment and Heritage Protection (EHP) is being used to identify additional areas of potentially suitable habitat as priorities for future survey effort.
The numbers of birds within northern NSW has been fairly consistent since 1996; with a current estimate of between 11 and 35 birds (Sandpiper Ecological Surveys 2012). The majority of birds in northern NSW now occur on private land (D. Charley pers. comm. 2010). Rohweder (Sandpiper Ecological Surveys 2012) discussed whether the dramatic decline in numbers between 1988 and 1996 could be due to stochastic events such as drought, severe fires, and substantial shifts in habitat (although severe drought between 2002 and 2005 and substantial fire-induced habitat change at some locations e.g. Richmond Gap have also occurred since 1996). Alternatively, the carrying capacity of locations (i.e. the ability of the location to sustain a population) may have declined in that period due to gradual changes in habitat quality, such as shrub growth and reduced ground cover (suggesting regular fires may be required to maintain grassy forests on southern aspects). However, evidence gathered since 1999 suggests that change is gradual and it is possible that the sharp decline recorded between 1988 and 1996 is partly due to an elevated population estimate in 1988 (Sandpiper Ecological Surveys 2012).
The northern population is vulnerable to further local declines (Holmes 1989, 1997; Stewart 1997, 1998; Sandpiper Ecological Surveys 2008, 2012; Whitby 2009; D. Stewart pers. comm. 2010).
The central populations make up the current stronghold of the species, consisting of two genetically isolated populations (Roberts et al. 2011) in the Illawarra and Jervis Bay regions of NSW. Scattered colonies of the Illawarra population occur at Budderoo NP and the adjoining Barren Grounds NR and in the Morton NP-Red Rocks NR area (Baker 1998; Barrett et al. 2003; DEC 2006). The population at Jervis Bay is found on a variety of tenures including NSW Jervis Bay NP, Booderee NP, HMAS CRESWELL, Beecroft Weapons Range, Shoalhaven City Council land and freehold lands. Approximately 10 percent of the Jervis Bay population occurs on private land (Bain and McPhee 2005).
Central Eastern Bristlebird populations have been well studied, surveyed and monitored in the last two decades (e.g. Baker and Whelan 1996; Baker 1998; Bain 2001; Bain and McPhee 2005). Ten years ago the central population was considered to be stable (Garnett and Crowley 2000). The populations have experienced temporary loss of habitat from a number of fire events since then, however monitoring of sub-populations has shown that the central populations can recover rapidly (e.g. Lindenmayer et al. 2009).
The central populations are estimated to comprise more than 2000 birds (see Table 1), including 1000 birds at Barren Grounds NR / Budderoo NP, 1000 birds at Jervis Bay and a small number of birds in a very small area at Morton NP-Red Rocks NR (Baker 1998; Bain and McPhee 2005).
In addition, two translocated populations have been established within the species’ original distribution. At Jervis Bay, 45 birds were translocated from Bherwerre Peninsula to Beecroft Peninsula between 2003 and 2005 (Bain et al. 2012), with a current estimate of more than 94 birds (Baker et al. 2012). In the Illawarra, 50 birds were translocated from Barren Grounds NR to the Woronora Plateau in 2008, with evidence of breeding and a current estimate of more than 15 birds (Baker et al. 2012).
The southern population occurs on the NSW/Victoria coastal border, in Nadgee NR (NSW) and the adjoining Croajingalong NP (Vic) at Howe Flat (Holmes 1982; Gosper and Baker 1997; Baker 1998; Clarke and Bramwell 1998; Barrett et al. 2003; Bramwell 2008).
In 1998, the southern population appeared to be stable (Baker 1998) with the prospect of the Nadgee sub-population naturally increasing provided there were no large-scale fires or other disruptions (Baker 1997). The current estimate is 380 birds (see Table 1) in an area of about 2800 ha. This includes estimated populations of 250 birds at Nadgee NR (L. Evans pers. comm. 2012) and 120-140 birds in 800ha of suitable habitat in the Howe Flat area of Croajingalong NP (Bramwell 2008). In 2009, a range extension into heathlands two to four kilometres north of Howe Flat in Croajingolong NP was recorded, increasing that population by an estimated 20 birds in approximately 100-150 ha of suitable habitat (M. Bramwell pers. comm. 2010).
The southern population of the Eastern Bristlebird is vulnerable to local extinction because of its small size and the high likelihood of widespread catastrophic fire. The Victorian Scientific Advisory Committee (SAC 1994) determined that the Eastern Bristlebird is significantly prone to future threats that are likely to result in local population extinction or significant declines in abundance or distribution.
The habitat of the Eastern Bristlebird is defined by a similar structure of low, dense, ground or understorey vegetation (Lamb et al. 1993; Clarke and Bramwell 1998; Chapman 1999; Baker 2000). The species occupies a broad range of vegetation types with a variety of species compositions, including grassland, sedgeland, heathland, swampland, scrubland, grassy sclerophyll forest and woodland, and rainforest (e.g. Smith 1977, 1987; Holmes 1989, 1998; Baker 1997, 2000; Chapman 1999; Miles 2004; Bramwell 2008). Eastern Bristlebird habitat primarily occurs as coastal, subcoastal and coastal escarpment scrubland / grassland / sedgeland and as open grassy forest on inland ranges (Blakers et al. 1984; Holmes 1989). Table 2 has been adapted from Baker (2000) and lists the varied vegetation types utilised by the Eastern Bristlebird in all populations.
Habitat Critical to Survival
All habitat currently occupied by the Eastern Bristlebird is critical to its survival.
Eastern Bristlebirds in the northern population mainly occur in scattered areas of montane open forest where the undergrowth is dense and grassy, and contains diverse structural features which provide the birds with protection and nesting locations. The ground-layer vegetation is usually about 1.0–1.5 m tall, providing about 65–90% ground cover. Typical ground cover includes tussock-grasses such as Sorghum leiocladum, and other grasses, with a variety of scattered small shrubs, woody herbs, patches of ferns and vine tangles (Holmes 1989, 1998; Lamb et al. 1993; Hartley and Kikkawa 1994; Sandpiper Ecological Surveys 2000a).
Birds in the northern population sometimes occur in other vegetation types such as heathland with stunted shrubs, or swampland with dense ferns and sedge tussocks. Habitat is typically either interspersed with, or adjacent to, mature subtropical rainforests, although some birds live up to 750 metres away from rainforest (Holmes 1989; Sandpiper Ecological Surveys 2000a; Stewart 2006). Adjacent rainforest or damp gullies are likely to be refuge areas for the birds during and after fires. In the more exposed situations, suitable habitat tends to be confined to intermittent watercourses (Holmes 1989, Hartley and Kikkawa 1994; Stewart 2006).
Central and Southern Populations
Birds in the central and southern populations have been recorded in a variety of vegetation communities with dense understorey. They often occur in low heathland, sometimes interspersed with thickets of taller shrubs or small trees (Loyn 1985; Pyke et al. 1995; Gosper and Baker 1997; Clarke and Bramwell 1998; Baker 1998, 2000; Bain and McPhee 2005; Bramwell 2008). The species also occurs in Gahnia sedgeland (Baker 1998) and in dense swamp shrubland or in coastal or riparian scrub and often with tussock-grasses or sedges in the understorey (White 1915; Pyke et al. 1995; Gosper and Baker 1997; Clarke and Bramwell 1998; Baker 1998, 2000; Higgins and Peter 2002; Bramwell 2008).
Birds sometimes occur in open sclerophyll woodland or forest, with a shrubby understorey and a dense ground layer of grasses or bracken (Emison et al. 1987; Bramwell et al. 1992; Pyke et al. 1995; Gosper and Baker 1997; Clarke and Bramwell 1998; Baker 1998, 2000; Bain and McPhee 2005; Bramwell 2008;). They occasionally occur in temperate rainforest that contains Acmena smithii (Emison et al. 1987; Clarke and Bramwell 1998; Baker 2000). In Croajingolong NP, Eastern Bristlebirds have also been recorded in rainforest along creeks and lowland forest dominated by Red Bloodwood Corymbia gummifera (DSE 1999).
In a recent study to select suitable habitat for translocations in Jervis Bay and the Woronora Plateau, Baker (2009) radiotracked 12 individual Eastern Bristlebirds and found that while heathland to woodland ecotones may provide suitable habitat for some individual Eastern Bristlebirds, the species is neither dependant on, nor confined to, heathland to woodland ecotones.
Woodland and low woodland with E. sieberi and understorey of dense shrubs and herbs
Scrub: coastal dune and riparian, coastal Melaleuca armillaris and Leptospermum laevigatum
Clarke & Bramwell (1998), Baker (2000)
Hind-dune swamp with Melaleuca ericifolia to 2 m in wetter areas and M. armillaris to 5 m, some Leptospermum juniperinum and dense herbs, e.g. Leptocarpus tenax, in drier areas
Clarke & Bramwell (1998), Baker (2000)
Wet heathland similar to closed swamp with Melaleuca squarrosa, M. ericifolia, Sprengelia incarnata, Gleichenia and/or dense herbs, e.g. Gymnoschoenus sphaerocephalus, Leptocarpus tenax, Lepidosperma forsythii or Xyris spp.
Clarke & Bramwell (1998), Baker (2000)
Low to tall closed heathland and heathland with Allocasuarina paludosa, Hakea ulicina and/or Banksia serrata
Nadgee Upland Heath
L. Evans pers. comm. (2010)
Wet forest/rainforest relic with Eucalyptus botryoides and Acmena smithii
Forest of E. pilularis, Corymbia gummifera and/or E. botryoides to 35 m
Open forest of E. obliqua, C. gummifera, E. cypellocarpa and/or E. fastigata to 35 m
Open forest of E. pilularis, Syncarpia glomulifera and/or C. gummifera to 25 m
Woodland with E. sclerophylla, C. gummifera and/or E. piperita to 15 m and dense understorey of herbs and shrubs
Woodland and open woodland of E. sieberi and/or C. gummifera 10-20 m and dense understorey of herbs and shrubs
Closed scrub of Banksia ericifolia, Allocasuarina distyla and/or Hakea teretifolia and of Melaleuca squarrosa
Closed coastal scrub of Leptospermum laevigatum
Closed shrub swamp
Mallee of C. gummifera or E. dendromorpha
Closed low (< 0.5 m) to tall (2 m) heathland with Banksia ericifolia, Xanthorrhoea spp., Sprengelia incarnata, Hakea teretifolia, H. dactyloides, Darwinia leptantha, Allocasuarina paludosa, Baeckea imbricata, B. linifolia, Banksia paludosa, Gleichenia spp. and/or Leptospermum juniperinum
Smith (1985), Baker (2000)
Closed sedgeland and closed wet heathland with Empodisma minus, Gymnoschoenus sphaerocephalus, Lepidosperma forsythii, Chorizandra sphaerocephala, Gahnia spp., Gleichenia spp. with taller shrub clumps of Sprengelia incarnata, Banksia ericifolia and/or Leptospermum juniperinum
Disturbed area of Blady Grass Imperata cylindrica with scattered Macrozamia communis and stunted wattles on deep latite soils. Adjacent to Illawarra Blue Gum Eucalyptus botryoides x saligna with small occurrences of Forest Red Gum Eucalyptus tereticornis up to 25m.
Gaia Research (2010)
Holmes (1989), Baker (2000)
Open forest with Eucalyptus saligna, Allocasuarina torulosa, E. andrewsii, Xanthorrhoea glauca, Acacia melanoxylon and/or A. implexa and understorey/ground cover of tussocks Imperata cylindrica, Poa sieberiana, P. labillardieri, Themeda spp., Sorghum leiocladum and/or bracken Pteridium esculentum: understorey may be dominated by weeds Lantana camara, Rubus spp. (blackberry) and Ageratina spp. (crofton and mist weeds), e.g. at Richmond Gap
Holmes (1989), Lamb et al. (1993), Baker (2000)
Mallee heath with E. approximans, shrubs, Gleichenia spp. and Gahnia spp. at Mt Barney
Eucalyptus crebra, E. tereticornis woodland on Cainozoic igneous
Regional Ecosystem 12.8.16 (DEHP 2011)
Eucalyptus dunnii tall open forest on Cainozoic igneous rocks
Regional Ecosystem 12.8.11 (DEHP 2011)
Montane shrubland on Cainozoic igneous rocks
Regional Ecosystem 12.8.19 (DEHP 2011)
Eucalyptus tereticornis, Corymbia intermedia open forest on metamorphics with or without interbedded volcanics. Higher altitudes
Regional Ecosystem 12.11.9 (DEHP 2011)
Mixed tall open forest with Eucalyptus siderophloia, E. propinqua on metamorphics with or without interbedded volcanics
Regional Ecosystem 12.11.3 (DEHP 2011)
Mixed tall open forest with Corymbia citriodora, Eucalyptus siderophloia, E. major on metamorphics with or without interbedded volcanics
Regional Ecosystem 12.8.5 (DEHP 2011)
Eucalyptus crebra woodland on metamorphics with or without interbedded volcanics
Regional Ecosystem 12.8.7 (DEHP 2011)
Table 2. Vegetation communities inhabited by Eastern Bristlebird
(adapted from Baker 2000 and Queensland DEHP Regional Ecosystem Mapping 2011) (As in Baker 2000, the names used for the vegetation communities generally follow Ingwersen (1976), Hermes & Jordan (1990) and Taws (1997) for the central populations, Gilmour (1983) for the southern populations and otherwise those of the cited authors.)
The Eastern Bristlebird is also occasionally recorded in sites dominated by invasive weeds such as Lantana, Bitou Bush, Blackberries (Rubus) and Mistflower (Ageratina riparia) (Gibson 1977; Lamb et al. 1993; Chapman 1999; Lindenmayer et al. 2009; E. Gould pers. comm.).
Habitat and Fire
The Eastern Bristlebird inhabits fire-prone habitats and the relationship between the species and fire has been well studied (e.g. Holmes 1989, 1998; Lamb et al. 1993; Baker 1997, 1998, 2000, 2003; Bramwell et al. 1992; Hartley and Kikkawa 1994; Clarke and Bramwell 1998; Bain and McPhee 2005; Bain et al. 2008; Lindenmayer et al. 2009), although ongoing research is being conducted to address existing knowledge gaps. The response of Eastern Bristlebird populations to fire is highly variable and strongly context-dependent (Bradstock et al. 2005; Bain et al. 2008), but they are particularly vulnerable to large-scale, intense fires (e.g. Clarke and Bramwell 1998; Baker 2000). The extent, intensity and frequency of fires are all important in determining habitat suitability.
Small-scale or low-intensity fires may leave small patches of unburnt habitat that provide refuge during fire and a base for the recolonisation of burnt areas post-fire. The presence of nearby unburnt habitat as a refuge is an important landscape component for the survival of Eastern Bristlebirds following fire (Holmes 1989; Pyke et al. 1995; Baker et al. 1997; Baker 1997, 2000; Bain et al. 2008). Birds may escape fire by temporarily moving to nearby unburnt vegetation and then return when conditions are suitable (Bain et al. 2008). Intense and/or extensive fires can eliminate large areas of suitable habitat, without leaving unburnt refuges, and lead to extinction of local populations (Baker 2000). Unburnt patches may result from topographic features such as wet depressions, drainage lines and escarpment edges (Whelan 1995; Baker 2000) or from fire suppression activities. The northern Eastern Bristlebird population utilises rainforest as a refuge from fire (Holmes 1989). For a refuge to be effective during a fire, it must be close and be accessible under the prevailing fire conditions (Baker 2000).
Frequent fires may prevent vegetation from becoming dense enough to be inhabited by the species and they are of greatest threat in fragmented or small areas of habitat. The central and southern populations may reach maximum densities in habitat that has not been burnt for at least 15 years (Baker 1997). In the Booderee NP sub-population, the recolonisation of burned habitat within two years of fire was attributed to the patchiness of the 2003 fire (leaving unburnt refuges) and the intensive fox control program (Lindenmayer et al. 2009; Lindenmayer et al. 2010). Lindenmayer et al. (2010) concluded that the decline of Eastern Bristlebirds after fire is largely due to the exposure to exotic predators following the loss of dense protective cover during a fire.
Hartley and Kikkawa (1994) found that, in the northern population, the structure and invertebrate fauna of the understorey could recover within six months to be suitable for foraging by the Eastern Bristlebird. The tussock grass habitat of the northern population may be suitable for breeding at two years post fire (Hartley and Kikkawa 1994). Grass cover exceeded pre-fire levels two years post fire at both Richmond Gap and Grassy Spur and declined 4-5 years after fire at both sites (Sandpiper Ecological Surveys 2007). To manage bristlebird habitat, it is important to understand the relationship between tussocks, which are used for nesting, and other ground vegetation such as Kangaroo Grass, which provide cover for foraging and shelter. Frequent fires have been shown to increase Kangaroo Grass cover at the expense of tussocks (Sandpiper Ecological Surveys 2007).
A fire regime that is too infrequent in the northern population could allow vegetation to become unsuitable for nesting through trees and shrubs becoming established and shading the growth of suitable grassy ground cover, grassy tussocks becoming too long and collapsing or weeds invading (Sandpiper Ecological Surveys 2000a). Different studies have proposed different fire intervals to maintain suitable habitat: 10-20 years (Holmes 1989); 5-15 years (Lamb et al. 1993) or, more recently 4-5 years (Sandpiper Ecological Surveys (2007). Buffer zones, mosaic burns and refuge areas are needed to protect the birds and their habitat from destructive wildfires (Hartley and Kikkawa 1994). Hartley and Kikkawa (1994) proposed that burning in the cooler winter months was preferred to avoid breeding season, and maximising regeneration of habitat.