NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Little Eagle Hieraaetus morphnoides (Gould 1841) is a medium-sized (45-55 cm) bird of prey that occurs in two colour forms: either pale brown with an obscure underwing pattern, or dark brown on the upperparts and pale underneath, with a rusty head and a distinctive underwing pattern of rufous leading edge, pale 'M' marking and black-barred wingtips. Both forms have a black-streaked head with a slight crest, a pale shoulder band on the upperwings, a rather short and square-tipped barred tail, and feathered legs. The very similar Whistling Kite Haliastur sphenurus is more slightly built, with no black head markings, a longer, rounded and unbarred tail, and weaker bare legs. The Square-tailed Kite Lophoictinia isura is more slender with a pale face, small bill and feet, short bare legs, and longer, boldly banded wingtips.
2. The Little Eagle occupies habitats rich in prey within open eucalypt forest, woodland or open woodland. Sheoak or acacia woodlands and riparian woodlands of interior NSW are also used (Marchant and Higgins 1993; Aumann 2001a). For nest sites it requires a tall living tree within a remnant patch, where pairs build a large stick nest in winter and lay in early spring. Young fledge in early summer. Generation length has been estimated as 10 years (Debus and Soderquist 2008). It eats birds, reptiles and mammals, occasionally adding large insects and carrion (Marchant and Higgins 1993; Aumann 2001b; Debus et al. 2007). It was formerly heavily dependent on rabbits, but following the spread of rabbit calicivirus disease, and consequent decline in rabbit numbers by 65-85% in the arid and semi-arid zones (Sharp et al. 2002), the Little Eagle is increasingly dependent on native prey. Most of its former native mammalian prey species in inland NSW are extinct (terrestrial mammals of rabbit size or smaller, e.g. large rodents, bandicoots, bettongs, juvenile hare-wallabies and wallabies: Van Dyck and Strahan 2008).
3. The Little Eagle is distributed throughout the Australian mainland excepting the most densely forested parts of the Dividing Range escarpment (Marchant and Higgins 1993). It occurs as a single population throughout NSW. The population in New Guinea is now classified as a separate species, the Papuan Booted Eagle Hieraaetus weiskei (Lerner and Mindell 2005).
4. In the 1990s, the Little Eagle was estimated globally as numbering tens of thousands to as many as 100 000 birds (Ferguson-Lees and Christie 2001). Given the low reproductive rate of 0.5-1.0 young per pair per year, maturity at two or three years, and a floating population of juvenile and immature eagles (Marchant and Higgins 1993), mature individuals probably comprise less than three-quarters of the population. Following the calicivirus induced reduction of rabbit prey, the species is thought to have declined greatly but accurate figures are not available.
5. In recent decades, the Little Eagle is believed to have undergone a moderate reduction in population size in NSW based on evidence from localised and broadscale surveys. It was reported in 79 one-degree grids in NSW in the first national bird atlas in 1977-81, at mostly high reporting rates (more than 40% of surveys per grid), with breeding recorded in 27 grids (Blakers et al. 1984). During the second national bird atlas in 1998-2002 it was recorded in 72 one-degree grids, at mostly low reporting rates (10-20% and less than 10% of surveys per grid), with breeding in 13 grids (Barrett et al. 2003). Its index of abundance (reporting rate) declined significantly by 39% in NSW and 14% nationally over the 20 year span between the two atlases. Assuming a linear decline this is equivalent to a state wide decline of 52% over 3 generations, (30 years), the time frame recommended by IUCN (2008) for estimating population change. The decline was across most bioregions of NSW, being greatest in the sheep-wheat belt (Barrett et al. 2003, 2007). A continuing decline in the population is also suggested by the decrease in breeding records between atlas surveys (c. 50%). The Little Eagle was not less likely to be detected in Atlas 2 versus Atlas 1 which used different survey methods (Barrett et al. 2003) and therefore comparison of the two atlases is unlikely to be significantly affected by survey bias.
6. The species has undergone a severe decline in the Australian Capital Territory, from 13 breeding pairs in the 1980s to 11 pairs in the 1990s and only two recorded in 2005-06 (Olsen and Fuentes 2005; Olsen and Osgood 2006). A more intensive ACT survey in 2007 found three pairs, which raised a total of four young in that year (Olsen et al. 2008). There has been a long-term decline in reporting rate of c. 50% in south-eastern NSW since the 1970s, with an accelerating trend since the 1990s (Bounds 2008). In the Blue Mountains the Little Eagle was common in the 1990s, but is now considered ‘very uncommon’ (S. Tredinnick in Debus et al. 2007). Its breeding productivity is declining on the Northern Tablelands, with some territory-holding males remaining unpaired, and one known pair having recently disappeared (Debus et al. 2007). As the Little Eagle is a resident, territorial species that is long-lived with low breeding productivity, and formerly had a low and stable density, its recent decline may be a long-term process that tracks habitat quality and overall prey biomass rather than a temporary fluctuation caused by short-term climatic variation or the calicivirus-induced decline in rabbits. Species of raptors that eat rabbits showed no consistent decrease in their survey rate between 1986-1990 and 1996-2000, whereas observations of some other raptors that are not rabbit predators decreased over this period (Steele and Baker-Gabb 2008; W. Steele pers. comm. 08/2008), suggesting that the recent declines among many raptor species are due to multiple factors.
7. The main threats to the Little Eagle are inferred to be clearing and degradation of its foraging and breeding habitat. Over 50% of forest and woodland has been cleared in NSW (Lunney 2004; Olsen et al. 2005). Important habitat on the NSW tablelands and western slopes, containing relatively high eagle breeding densities until the 1980s, are 53-84% cleared and moderately to highly stressed (landscape stress factor 3-6 out of 6: Morgan 2000; Barrett et al. 2007). Some other important western bioregions are up to 40% cleared and/or have landscape stress ratings of 2-4 (e.g. Riverina, Darling Riverine Plains, Murray-Darling Depression, Mulga Lands, Broken Hill Complex: Morgan 2000; Barrett et al. 2007). Direct human threats to habitat are most evident around expanding provincial cities, where urbanisation and rural-residential expansion are displacing breeding pairs (e.g. Canberra: Olsen and Fuentes 2005; Olsen and Osgood 2006; Olsen et al. 2008). Loss of breeding sites may bring the Little Eagle into increasing interspecific competition with the larger, dominant Wedge-tailed Eagle Aquila audax (Olsen and Fuentes 2005; Olsen and Osgood 2006; Olsen et al. 2008; Debus et al. 2007). Secondary poisoning from pindone used to control rabbits is listed as a possible threat. 'Clearing of native vegetation' is listed as a Key Threatening Process in NSW under the Threatened Species Conservation Act 1995.
8. The Little Eagle is listed as a Vulnerable species in the Australian Capital Territory.
9. The Little Eagle Hieraaetus morphnoides (Gould 1841) is not eligible to be listed as an Endangered or Critically Endangered species.
10. The Little Eagle Hieraaetus morphnoides (Gould 1841) is eligible to be listed as a Vulnerable species as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:
Clause 14
The species has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time frame appropriate to the life cycle and habitat characteristics of the taxon:
(c) a moderate reduction in population size,
based on:
(d) an index of abundance appropriate to the taxon, and
(e) geographic distribution, habitat quality or diversity, or genetic diversity.
Dr Richard Major
Chairperson
Scientific Committee
Proposed Gazettal date: 12/02/10
Exhibition period: 12/02/10 – 09/04/10
References:
Aumann T (2001a) Breeding biology of raptors in riparian environments in the south-west of the Northern Territory, Australia. Emu 101, 305-315.
Aumann T (2001b) An intraspecific and interspecific comparison of raptor diets in the south-west of the Northern Territory, Australia. Wildlife Research 28, 379-393.
Barrett G, Silcocks A, Barry S, Cunningham R, Poulter R (2003) 'The new atlas of Australian birds.' (RAOU: Melbourne)
Barrett GW, Silcocks AF, Cunningham R, Oliver DL, Weston MA, Baker J (2007) Comparison of atlas data to determine the conservation status of bird species in New South Wales, with an emphasis on woodland-dependent species. Australian Zoologist 34, 37-77.
Blakers M, Davies SJJF, Reilly PN (1984) 'The atlas of Australian birds.' (Melbourne University Press: Melbourne)
Bounds J (2008) Nomination of a vulnerable species to the ACT Flora and Fauna Committee: Little Eagle. Canberra Bird Notes 33, 84-95.
Debus SJS, Hatfield TS, Ley AJ, Rose AB (2007) Breeding biology and diet of the Little Eagle Hieraaetus morphnoides in the New England region of New South Wales. Australian Field Ornithology 24, 137-157.
Debus SJS, Soderquist TR (2008) Report for Review of Species for the NSW Scientific Committee: Little Eagle Hieraaetus morphnoides.
Ferguson-Lees J, Christie DA (2001) 'Raptors of the world.' (Helm: London)
IUCN (2008) 'Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.' (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland).
Lerner HRL, Mindell DP (2005) Phylogeny of eagles, Old World vultures, and other accipitridae based on nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37, 327-346.
Lunney D (2004) A test of our civilisation: Conserving Australia's forest fauna across a cultural landscape. In 'Conservation of Australia's forest fauna (2nd edn)'. (Ed. D Lunney) pp. 1-22. (Royal Zoological Society of NSW: Sydney)
Marchant S, Higgins PJ (Eds) (1993) 'Handbook of Australian, New Zealand and Antarctic birds (vol. 2).' (Oxford University Press: Melbourne)
Morgan G (2000) 'Landscape health in Australia: A rapid assessment of the relative condition of Australia's bioregions and subregions.' (Environment Australia: Canberra)
Olsen J, Fuentes E (2005) Collapse in numbers of breeding Little Eagles in the Australian Capital Territory. Canberra Bird Notes 30, 141-145.
Olsen J, Osgood M (2006) Numbers of breeding Little Eagles in the Australian Capital Territory in 2006. Canberra Bird Notes 31, 178-182.
Olsen J, Osgood M, Maconachie M, Dabb G (2008) Numbers of breeding Little Eagles Hieraaetus morphnoides in the Australian Capital Territory in 2007. Canberra Bird Notes 33, 77-80.
Olsen P, Weston M, Tzaros C, Silcocks A (2005) The state of Australia’s birds 2005: Woodlands and birds. Supplement to Wingspan 15(4), 32 pp.
Sharp A, Gibson L, Norton M, Ryan B, Marks A, Semeraro L (2002) The breeding season diet of the Wedge-tailed Eagle (Aquila audax) in western New South Wales and the influence of Rabbit Calicivirus Disease. Wildlife Research 29, 175-184.
Steele W, Baker-Gabb D (2008) A national community-based survey of the diurnal birds of prey. Abstracts of the Australasian Raptor Association conference, Coffs Harbour, August 2008.
Van Dyck S, Strahan R (Eds) (2008) 'The mammals of Australia (3rd edn).' (Reed New Holland: Sydney)