Justification of Red List Category
This species has a very small range and very small breeding population in ongoing decline, and is therefore classified as Endangered.
Although the Riverland Biosphere Reserve (formerly the Bookmark Biosphere Reserve) supported an estimated 3,760 individuals, this was thought to equate to an effective population size of only 390 (210-726) mature individuals owing to a skewed sex ratio and a complex social organisation (Clarke et al. 2005). This population represented over 95% of the total effective population, hence, given the broad confidence intervals the population is probably best estimated to fall within the band 250-1,000 mature individuals. The surveys for the estimates by Clarke et al. (2005) were carried out following a series of good breeding seasons, and thereafter the population underwent a significant decline following a large fire and drought in the region. Favourable conditions since the drought broke has seen a population increase over the last eight years but not yet to the level of the early 2000 population estimate (R. Boulton in litt. 2016).
Historically, it declined dramatically owing to clearance and fragmentation of its preferred mallee habitat. As a result, hybridisation with the dominant M. flavigula, which invades remnant habitat patches, is now the greatest threat and continues to drive declines. The Millennium Drought may have affected the population, fires burned all the suitable habitat in the Bronzewing Fauna and Flora Reserve, and fires have reduced the suitable habitat available in the Bookmark Biosphere Reserve (R. Clarke and R. Boulton in litt. 2016).
Manorina melanotis is endemic to the Murray Mallee region of South Australia, Victoria and New South Wales, Australia, and is thought to have been distributed throughout most of this region prior to European settlement (Clarke et al. 2001). Range and numbers declined dramatically during the 1990s. In 1995, it was reported that just 28 birds were known in the wild, in north-west Victoria. Searches for the species in South Australia during the 1980s and New South Wales in 1993 were unsuccessful in locating the species (Clarke 2007). Conservation measures have since assisted the species's recovery. Extensive surveys during 2000-2002 found that the Riverland Biosphere Reserve (formerly the Bookmark Biosphere Reserve) in South Australia supported c.3,750 individuals, although the effective population size was only 390 (210-726) due to a skewed sex ratio (adults: 1 female: 1.8 males) and the species's complex social organisation (Clarke et al. 2005). This represented over 95% of the species's total effective population. These surveys were conducted during an upward population fluctuation (Clarke et al. 2005), following a series of good seasons, and the population may now stand at the lower end of these estimates owing to a drought in the region and a fire in 2006 and 2014 (R. Clarke and R. Boulton in litt. 2016). A smaller population estimate of 53 (32-85) colonies of pure and hybrid birds (from interbreeding with the Yellow-throated Miner M. flavigula) persists in the Murray Sunset National Park (Baker-Gabb 2007), with an addition two hybrid colonies in Annuello Flora and Fauna Reserve (Boulton 2014), but the small colonies at Scotia Sanctuary and Tarawi Nature Reserve and Bronzewing Flora and Fauna Reserve have been extirpated.
The species occupies semi-arid mallee habitats, that is, eucalyptus woodland in which individual trees are multi-stemmed from ground level and seldom taller than 10 m (Clarke et al. 2005). Densities are highest in areas containing mallee-Triodia associations, or mallee with an open understorey, situated at least 2 km from clearings that exceed 100 ha (Clarke et al. 2005), that has not been heavily grazed or burnt for 45 years. The species occupies mallee that has remained unburnt for at least 20 years (Clarke 2007), but it is unknown whether there is a maximum age after burning when habitat becomes unsuitable. However, anecdotal evidence suggests that mallee unburnt for at least 150 years (becoming park-like open woodland) is only occupied by M. flavigula. The required area of intact mallee for a viable population may exceed 13,000 ha (Clarke et al. 2005). The species's distribution in Victoria is positively correlated with stable dunefields with a relatively high loam level, amount of decorticating bark (from which it obtains much of its insect food), tree density, stem density, canopy cover and litter cover. The presence of a mosaic of burn types may have facilitated the genetic isolation of the species from M. flavigula. Populations can breed continuously for over 12 months given favourable conditions such as periods of above average rainfall (Clarke et al. 2005). A study of one colony found that 81.8% of females and only 13.9% of males bred per season (E. Moysey per Clarke et al. 2005). It is a cooperative breeder with up to 13 helpers, mostly males, assisting the nest of a breeding pair (E. Moysey per Clarke et al. 2005). Colonies may wander over areas of 8-10 km2 in the non-breeding season, although they show high breeding-site fidelity (Clarke 2007). Their diet consists of invertebrates and lerp and also nectar.
The fundamental reason for its decline is the clearance of the majority of favourable habitat. Although European settlers reached the Murray Mallee region in 1860s, it was not until the early 20th century that widespread clearing for cropping and pasture began, and in the 1930s pastoralists dug dams and drains and cleared vegetation to increase water flow (Clarke 2007). This has resulted in displacement of M. melanotis in habitat remnants by M. flavigula, and interbreeding between the two species is now the greatest threat to M. melanotis. The purity of the Riverland Biosphere Reserve colony is only maintained through active removal of hybrids, while both the Murray-Sunset colonies have Yellow-throated Miner among them. Recent introgression is particularly evident in isolated colonies that occur in small areas of remnant habitat (Clarke et al. 2005). A study of specimens of M. melanotis and M. flavigula from museums world wide, suggests that hybridisation increased markedly around the middle of the 20th century as dam construction and mallee clearance further increased (Clarke 2007). Isolated colonies have a low rate of recruitment, either as a result of elevated rates of nest-predation or as a result of emigration from the natal colony. Much remaining habitat in Victoria and New South Wales has been burnt within the last 25 years. The populations at Riverland Biosphere Reserve (formerly the Bookmark Biosphere Reserve) and Murray Sunset National Park are at high risk of extinction from large-scale wildfire (Clarke et al. 2005). A single large fire in Murray Sunset NP rendered over half of the remaining prime habitat unsuitable for the species between 1980 and 1990 (Clarke et al. 2005), and habitat fragmentation now means that fires can burn whole reserves (Clarke et al. 2005). A fire in the Riverland Biosphere Reserve in late November and early December 2006 burnt 115,000 ha of mallee habitat, including much of the core area for the species and reducing the area of available habitat for the species by about a third, or possibly more, but creating a natural fire break for unburnt areas (R. Clarke in litt. 2007). Accurate density estimates for the 2006 fire scar have not yet been produced, but densities in unburnt patches close to the fire edge may be only slightly lower than within unburnt core areas (R. Boulton in litt. 2016). Areas away from the fire edge where the fire burnt more homogenously have not been surveyed to date. The modern ability to suppress fires has likely resulted in a reduction in the proportion of fires at a moderate scale (100 ha - 10,000 ha), which tend to burn at a variety of intensities providing patchiness and fire refuges (Clarke et al. 2005). The species is thought to be prone to fluctuations in response to variable climatic conditions, with extended periods of drought limiting breeding and periods of above average rainfall promoting extended breeding (R. Boulton per Clarke et al. 2005); observations suggest the average change in colony size could be c.50% either way (Clarke et al. 2005). Fires burned all the suitable habitat in the Bronzewing Fauna and Flora Reserve, where the species is now extirpated. Displacement by by M. flavigula is probably the reason for recent extirpations from Scotia and Tarawi.
Conservation Actions Underway
In reaction to the species's very low numbers in the mid-1990s, a colony of seven males and two females was taken into captivity in order to establish a captive breeding colony (Clarke 2007). Management actions completed or underway include genetic studies, regular surveys and monitoring, the study of habitat preference in Victoria, the purchase of leases within Riverland Biosphere Reserve, the adoption of a policy of rapid fire suppression within mallee in Victoria and South Australia, research into reproductive biology and ecology, establishment of a captive population, colony translocations, generation of community support and the establishment of a recovery team (Clarke et al. 2002). The threat of M. flavigula is tackled by the closure and revegetation of dams, and strategic removal of colonies (Clarke 2007). Between 1996 and 2002 intensive field studies located a previously unknown population and a number of isolated colonies throughout the species's historic range (Clarke et al. 2005). These searches identified what is now known to be the largest population of the species, in the Riverland Biosphere Reserve (Clarke et al. 2005). In 2000 and 2001, 60 adult and 30 young birds were successfully translocated from the Riverland Biosphere Reserve to the Murray-Sunset National Park (Clarke et al. 2002). These trial translocations were the first to translocate such a social, cooperative breeding bird, with whole intact colonies containing multiple females that went on to successfully maintain colony cohesiveness and breed after release. In 2003, 45 captive reared birds were released in the Bronzewing Flora and Fauna reserve, Victoria, and unsuccessful breeding attempts occurred within days of release (Clarke 2004). In 2005, surveys revealed that unsuccessful breeding attempts were still taking place amongst at least 11 surviving captive-reared birds and other unringed birds, and observations suggested that successful breeding had occurred, with a possible offspring from a previous nest acting as a helper (Clarke 2006). A Black-eared Miner Recovery Team has been formed.
23-26 cm. Medium-sized, grey honeyeater with black face mask, grey rump and tail concolorous with back. Sexes alike. Mid- to dark grey upperparts. Olive-yellow edged remiges and outer rectrices. Black mask from bill to ear-coverts. Dark grey, sub-moustachial stripe. Grey chin and upper throat, finely mottled on breast. White belly. Yellow bill and skin behind eye. Juvenile more brown. Similar spp. Yellow-throated Miner M. flavigula has white-tipped tail and whitish rump. Hybrid melanotis x flavigula has pale-tipped tail, paler grey on rump and sub-moustachial stripe. Voice Variety of harsh notes, chattering.
Text account compilers
Allinson, T, Benstead, P., Dutson, G., Garnett, S., McClellan, R., Symes, A., Taylor, J.
BirdLife International (2021) Species factsheet: Manorina melanotis. Downloaded from http://www.birdlife.org on 21/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2021.