2 AUSTRALIAN FIELD ORNITHOLOGY 2008, 25, 2–11 The Eastern Bristlebird Dasyornis brachypterus in East Gippsland, Victoria, 1997–2002 MICHAEL D. BRAMWELL Department of Sustainability and Environment, Bairnsdale, Victoria 3875 (Email: [email protected]) Summary This paper presents results from surveys to determine the distribution and abundance of the Eastern Bristlebird Dasyornis brachypterus and its Ecological Vegetation Class (EVC) preference from Howe Flat (5 km east of Mallacoota, Victoria) to Nadgee Nature Reserve in New South Wales over the period 1997–2002. A total of 1055 ha was surveyed, yielding 50 Bristlebird detection sites. A clear preference for Riparian Scrub Complex was recorded, with 38 of 50 Bristlebirds being detected within that EVC. At Bristlebird detection sites, ground-cover sedge species were the plants recorded most frequently and at the highest cover/abundance values; shrubs >1.5 m tall were recorded with a higher cover/abundance than shrubs <1.5 m. Forty-six of the 50 detections were from Howe Flat, and an estimated 60–80 pairs at a population density of 15–20 birds/100 ha were found there. Habitat is mostly unsuitable over the 10 km between the eastern edge of Howe Flat and recorded Bristlebird habitat in Nadgee Nature Reserve. Hence, the southern population of Eastern Bristlebirds should be managed as two subpopulations. Six other areas throughout Gippsland were also surveyed for Eastern Bristlebirds, but no Bristlebirds were recorded at any of these sites. Introduction The Eastern Bristlebird Dasyornis brachypterus is one of four bird species in Victoria considered endangered at both a state and national level (DSE 2003). It is also endangered in the other states where it occurs, New South Wales (NSW) (Baker 1997) and Queensland (critically so: Stewart et al. 2004). In response, conservation agencies and volunteer bird-watchers across south-eastern Australia are working together to better understand and manage the species and its habitat (e.g. Stewart et al. 2004; Bain & McPhee 2005; Clarke & Bain 2006). This paper presents survey information for Eastern Bristlebirds in Victoria from 1997 to 2002. Eastern Bristlebirds, very poor flyers, are small (~40 g), shy, cryptic, predominantly ground-feeding insectivores that nest in grass and sedge tussocks <50 cm above the ground (see Garnett & Crowley 2000, Higgins & Peter 2003 and Gibson & Baker 2004 for details of biology). Population densities vary greatly depending on available habitat, with a maximum density of about four birds per 10 ha (Baker 2001). Detection largely involves knowledge of the Bristlebird’s vocal behaviour, with call-playback a useful supplementary survey technique (see Clarke & Bramwell 1998; Baker 2001; Higgins & Peter 2003; Bain & McPhee 2005). The Eastern Bristlebird was formerly distributed patchily from the Conondale Range, south-eastern Queensland, along the coast and adjacent ranges to Marlo in eastern Victoria (Baker 1997; Garnett & Crowley 2000; Higgins & Peter 2003). There are also unconfirmed reports from South Gippsland and Wilsons Promontory (Cooper 1975; Emison et al. 1987; Mitchell 1995; C. Doughty pers. comm.). Throughout its range the species has declined substantially over the last 50 years (Baker 1997; Garnett & Crowley 2000; Higgins & Peter 2003; Stewart et al. 2004). VOL. 25 (1) MARCH 2008Eastern Bristlebird in Victoria 3 The southern population near Cape Howe (East Gippsland, Victoria) occurs in Nadgee Nature Reserve, NSW, and at Howe Flat, east of Mallacoota in Croajingolong National Park, Victoria. The combined Nadgee/Mallacoota population has been estimated at <50 pairs, with 26 birds in Nadgee (Baker 1997; Gosper & Baker 1997). The species has been recorded in diverse vegetation types that provide low, dense cover, throughout its past and present range (see Baker 2000 and Higgins & Peter 2003 for detailed reviews, and Emison et al. 1987, Bramwell et al. 1992 and Pyke et al. 1995 for the central and southern populations). In East Gippsland there are Bristlebird records from coastal and foothill areas of dense heath, wet heathland, Melaleuca thickets, rainforest, lowland forest with a dense, heathy or teatree understorey, dense teatree thickets, coastal scrub and riparian forest. A common theme through all these vegetation types is a dense cover of understorey or ground vegetation or, in the case of rainforest, a refuge from fire. It appears that Eastern Bristlebird populations occur where a mosaic of vegetation types exists within a certain area. The central population requires specific structural vegetation characteristics, such as thick ground-cover with either tall shrub or low tree cover (Baker 2000). The vegetation types inhabited by Eastern Bristlebirds are fire-prone, with fire management a major issue for Bristlebird conservation. Bristlebird densities in the central population have steadily increased with increasing fire age of the vegetation (Baker 1997, 2000; Bain & McPhee 2005). Large-scale, intense fires have been implicated in the demise of the species throughout its range (Baker 1997, 2000; Clarke & Bramwell 1998; Garnett & Crowley 2000; Higgins & Peter 2003; Stewart et al. 2004). The only fire recorded on Howe Flat was on 16 September 1981, when the eastern half of the Flat was burnt (G. Cameron pers. comm.). In East Gippsland, 10 past record localities up to 1995 were surveyed for Eastern Bristlebirds, with the only positive record being for Howe Flat (Clarke & Bramwell 1998). Seven Ecological Vegetation Classes (EVCs: see Woodgate et al. 1994) have been mapped across Howe Flat, indicating the complex vegetation dynamics. Clarke & Bramwell (1998) identified Riparian Scrub as the most favoured EVC in which Eastern Bristlebirds were historically observed, and the EVC in which they were observed at Howe Flat. However, it is unknown whether other EVCs across their range also support Bristlebirds. Hence, the habitat preference for Bristlebirds at Howe Flat is largely unknown. Similarly, Clarke & Bramwell (1998) estimated a population density of six birds in 32 ha, based on a single visit. This result required a more systematic survey of the area to determine the population density and size. The first confirmed record of the Eastern Bristlebird in the Mallacoota area was of two specimens from near Lake Barracoota in 1914 (Chaffer 1954; Wakefield 1958). In 1947 the species was recorded ‘7 miles from Mallacoota’ (Howe 1947), and in 1958–59 D.G. Morgan observed Eastern Bristlebirds in dense teatree at Howe Flat and at Lake Barracoota, Point Hicks and Shipwreck Creek (VORG 1962). Dorwood (1976) recorded the species ‘about 2 km north of Lake Barracoota’. No Bristlebird surveys or records exist for the coastal areas east of Howe Flat to the NSW border, although EVC maps indicate suitable habitat. Bristlebirds occur in the south of Nadgee Nature Reserve, near the Victorian border (Gosper & Baker 1997). AUSTRALIAN 4BRAMWELL FIELD ORNITHOLOGY Since 1994, there have been four Eastern Bristlebird records in Gippsland away from the Howe Flat area: Bald Hills Wildlife Reserve in South Gippsland, two from Croajingolong National Park, and one from the Cann River Bushland Reserve. These require urgent checking and confirmation, as do historical unconfirmed records from Wilsons Promontory National Park and potential habitat identified in the Croajingolong National Park. The objectives of the surveys described in this paper were to: (1) determine the distribution and abundance of Eastern Bristlebirds in the Howe Flat to Nadgee Nature Reserve area; (2) determine whether the Howe Flat and Nadgee Nature Reserve subpopulations are linked as a single population; (3) determine the EVC preference, and other EVCs in close proximity, for Eastern Bristlebirds in the Howe Flat to Nadgee Nature Reserve area; and (4) determine the presence or absence of the species from localities with records since 1994 and in areas of potential habitat that had not been surveyed by Clarke & Bramwell (1998). Study area and methods Howe Flat to Nadgee Nature Reserve survey Surveys for Eastern Bristlebirds were conducted in 28 areas of known and potential near-coastal habitat from Mallacoota to Cape Howe in East Gippsland (based on previous Bristlebird records and known habitat preference: Figure 1). Within this study area, surveys were completed in early spring to avoid the Victorian breeding season of the Bristlebird (and hence possible effects of disturbance on nesting). Surveys around the Howe Flat area were carried out on 23–26 September 1997 and 28 September–1 October 1998, and the Cape Howe and Lake Wau Wauka area on 29–30 September 1999. Surveys south and east of Lake Barracoota were carried out on 13–14 October 2000. Five people conducted the surveys; all were familiar with the calls of the Eastern Bristlebird and could distinguish these from similar calls such as those of Pilotbirds Pycnoptilus floccosus and New Holland Honeyeaters Phylidonyris novaehollandiae. Volunteers also assisted the survey team. Most surveys were conducted by two experienced surveyors, but occasionally one or three surveyors were employed. At each search area, surveyors walked through the area ~100 m apart (except for the Lake Wau Wauka area where a canoe was used in addition to walking). Radio contact was maintained between surveyors. In an attempt to elicit a response from Bristlebirds after mid morning, surveys after 0900 h were accompanied by playback of Bristlebird calls. On each occasion the tape was played for several minutes, followed by a short listening period. From a pilot study it seemed that the playback call could be heard for 100 m, as could any calling Bristlebirds (see Bramwell et al. 1992), so this distance was used in determining the area searched. The area covered during each search (9.5–103 ha) was plotted on 1:25 000 maps. All surveys were conducted between 0610 and 1230 h; most were concluded before 1000 h, and lasted between 30 and 300 minutes (for a total of 77 h of surveys). Only on cooler days when activity and vocalisation of other passerines remained high did surveys continue past 1000 h.