Grey Falcon Falco hypoleucos - endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Grey Falcon Falco hypoleucos Gould, 1841 as an endangered species in Part 1 of Schedule 1 of the Act, and as a consequence, to omit reference to the Grey Falcon Falco hypoleucos Gould, 1841 from Part 1 of Schedule 2 (Vulnerable species) of the Act. Listing of Endangered species is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. The Grey Falcon Falco hypoleucos Gould, 1841 is a medium-sized (30-45 cm), pale grey falcon with prominent yellow cere (enclosing the nostrils), eye-rings (around dark eyes) and feet. The upperparts are light grey with a faint black streak below the eyes, black tips to the long pointed wings, and barred wings and tail. The underparts are pale grey to white, with faintly barred underwings and tail. The juvenile is slightly darker and more heavily marked, with blue-grey cere and eye-rings and fine streaks on the underparts.

 

2. The Grey Falcon of inland Australia is widely but sparsely distributed in woodland, shrubland and grassland in the arid and semi-arid zones, especially wooded watercourses, of mainland Australia. In NSW it occurs on the plains of the Murray-Darling Basin, and particularly west of the Darling River. Falcons (including the Grey) are highly mobile, commonly travelling over hundreds of kilometres (Marchant & Higgins 1993). Most reports of 'Grey Falcons' on the tablelands and coast of NSW are almost certainly referable to the Grey Goshawk (Accipiter novaehollandiae) (Debus & Soderquist 2009). Easterly records to the foothills of the western slopes are valid (Martin & Royal 2000), but most validated records (including recent ones) are from farther inland in the arid and semi-arid zones (Barrett et al. 2003; NSW Field Ornithologists Club 1990-2007). Even inland records, historical and recent, may be inflated by misidentified raptors of other species.

 

3. The Grey Falcon preys mostly on birds, especially flocking, ground-feeding granivores (e.g. pigeons and parrots), and also on some small mammals, reptiles and large insects. Grey Falcons also take the introduced Common Starling (Sturnus vulgaris) in agricultural areas, which may function as a transfer path for pesticide contamination in the falcons. Although a few of its prey species are common in agricultural or pastoral land with stock watering points, food supply of the Grey Falcon is likely to be adversely affected by habitat clearing and degradation.

 

4. The Grey Falcon uses old stick nests, typically built by crows or ravens or sometimes other raptor species, in the top of an emergent tree in riparian woodland. Occasionally, Grey Falcons will nest on an artificial structure such as a telecommunications tower (J. Schoenjahn in litt. 2009). A clutch of usually two or three eggs is laid between winter and late spring. The incubation period is five weeks, the nestling period six to seven weeks, and the post-fledging dependence period lasts several months.

 

5. The number of breeding Grey Falcons in Australia has been previously estimated as 2 000 (Garnett & Crowley 2000), of which fewer than one-quarter would occur in NSW; or fewer than 500 mature individuals on the basis of geographic range as the highest densities are in northern and inland Australia (Barrett et al. 2003). NSW bird atlas records have shown that the Grey Falcon has been recorded in 17 one-degree grids of c. 100 x 100 km: (Barrett et al. 2003). Although the global estimate is assigned a low level of reliability (Garnett & Crowley 2000), the estimated total population in NSW is still well below the IUCN threshold of 2 500 mature individuals for Endangered status (IUCN 2008). One estimate suggests the population of Grey Falcons in NSW could be as low as 50 to 200 mature individuals (J. Schoenjahn in litt. 2009). Should additional information on population size become available, the species may warrant re-assessment.

 

6. The Grey Falcon has declined in NSW, and its breeding range has contracted from within the 500 mm rainfall isohyet to within the 250 mm isohyet (i.e. a contraction to the arid zone: Marchant & Higgins 1993; Garnett & Crowley 2000). Although generally sparse in NSW, the Grey Falcon was said to be formerly numerous in the far south-west of NSW, but is now rarer there (Marchant & Higgins 1993). However, during the 1990s since the ban on the use of DDT, several breeding records have been reported from the semi-arid zone (Debus & Rose 2000; Martin & Royal 2000), although this does not represent a recovery and there is no evidence that Grey Falcons have persisted into the drought years since 2000 (NSW Field Ornithologists Club 1990-2007).

 

7. In NSW the decline of the Grey Falcon in the sheep-wheat belt has been attributed to declining habitat cover and deteriorating habitat quality (Marchant & Higgins 1993; Garnett & Crowley 2000). In the five years since the second national bird atlas (i.e. during 2002 – 2007), the Grey Falcon was recorded once in each of only two inland NSW grids: once in 100 surveys and once in 22 surveys (Birds Australia Atlas data). While these latest figures suggest continued decline, the recent atlas surveys have continued at a lower level than between 1998-2002, making direct comparisons impossible.

 

8. There is no direct evidence of extreme fluctuations in the Grey Falcon population. However, the number of birds reported in NSW each year varies by a factor of 3-4 (NSW Field Ornithologists Club 1990-2007), and breeding pairs abandon nesting territories during drought (Marchant & Higgins 1993; Aumann 2001). Drought refuges are not permanent in Australia, sometimes located around coastal areas, and sometimes in areas such as the Murray-Darling confluence (Marchant & Higgins 1993). The size of the NSW Grey Falcon population is therefore likely to respond to seasonal conditions.

 

9. The main threats to the Grey Falcon are thought to be clearing of habitat in the semi-arid zone, and degradation of habitat in the arid and semi-arid zones by overgrazing, with likely effects on the Grey Falcon’s foraging habitat, nest sites and food supply (Marchant & Higgins 1993; Ayers et al. 1999; Garnett & Crowley 2000). The Grey Falcon may be affected particularly by the loss of riparian nest trees. 'Clearing of native vegetation', and ‘Removal of dead wood and dead trees’, are recognised as Key Threatening Processes in NSW under the Threatened Species Conservation Act 1995. Some inland bioregions (Brigalow Belt South, NSW South Western Slopes, Darling Riverine Plains, Riverina) are 40-84% cleared and moderately to highly stressed (landscape stress factor 2-5, mostly 3-5, out of a maximum of 6: Barrett et al. 2007). Even little-cleared bioregions farther west are moderately stressed (e.g. Mulga Lands, Murray-Darling Depression, Broken Hill Complex with stress rating of 4; Cobar Peneplain, Channel Country, Simpson-Strzelecki Dunefields with a stress rating of 3: Barrett et al. 2007).

 

10. The Grey Falcon may also be threatened by the limited supply of suitable nest trees. The species competes for nest sites with other falcon species such as the Nankeen Kestrel (faclo cenchroides) and possibly the Brown Falcon (Falco berigora) (J. Schoenjahn in litt.), and loss of nest trees, or failure of crows to breed and therefore build nests during prolonged periods of drought, can limit the availability of suitable nest sites for the Grey Falcon.

 

11. Other possible, but low-level, threats to the Grey Falcon include human disturbance to nest sites (including possible robbery of eggs or chicks), pesticides (Olsen et al. 1993; Debus & Rose 2000), and collision hazards with human structures such as powerlines, fences and wind turbines. There have been no recent documented cases of poaching in NSW, and the use of DDT has been banned, so the effect of this pesticide on the species has presumably been eliminated (as for the Peregrine Falcon, Falco peregrinus), although the effect of other pesticides (including locust sprays) is unknown.

 

12. Grey Falcon Falco hypoleucus Gould, 1841 is not eligible to be listed as a Critically Endangered species.

 

13. Grey Falcon Falco hypoleucos Gould, 1841 is eligible to be listed as an Endangered species as, in the opinion of the Scientific Committee, it is facing a very high risk of extinction in New South Wales in the near future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

 

Clause 16

The estimated total number of mature individuals of the species is:

(b) low,

and:

(d) a projected or continuing decline is observed, estimated or inferred in:

(i) an index of abundance appropriate to the taxon, and

(ii) geographic distribution, habitat quality or diversity, or genetic diversity.

 

 

Dr Richard Major

Chairperson

Scientific Committee

 

Proposed Gazettal date: 13/08/10

Exhibition period: 13/08/10 - 08/10/10

 

References:

 

Aumann T (2001) Breeding biology of raptors in riparian environments in the south-west of the Northern Territory, Australia. Emu 101, 305-315.

 

Ayers D, Nash S, Baggett K (1999) ‘Threatened species of western New South Wales (revised edn).’ (NSW NPWS: Hurstville)

 

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.

 

Debus SJS, Rose AB (2000) Diet of Grey Falcons Falco hypoleucos breeding extralimitally in New South Wales. Australian Bird Watcher 18, 280-281.

 

Debus SJS, Soderquist T (2009) Review of Species for the NSW Scientific Committee: Grey Falcon: Unpublished report to the NSW Scientific Committee.

 

Garnett S, Crowley G (Eds) (2000) ‘The action plan for Australian birds 2000.’ (Environment Australia: Canberra)

 

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). (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf).

 

Marchant S, Higgins PJ (Eds) (1993) ‘Handbook of Australian, New Zealand and Antarctic birds (Vol. 2).’ (Oxford University Press: Melbourne)

 

Martin WK, Royal MJ (2000) Easterly records of the Grey Falcon in New South Wales. Australian Bird Watcher 18, 132-134.

 

NSW Field Ornithologists Club (1990-2007) NSW annual bird reports and rare bird reports, published annually in Australian Birds and the Birding NSW Newsletter.

 

Olsen P, Fuller P, Marples TG (1993) Pesticide-related eggshell thinning in Australian raptors. Emu 93, 1-11.

Page last updated: 28 February 2011