The grey falcon (Falco hypoleucos) is a rare medium-sized falcon, one of the enigmatic ‘mystery’ birds of Australia, neither easily nor predictably seen. Recent studies however have contributed to the gathering of further information on this elusive bird of prey. One of the reasons behind this lack of information could be the difficulty in identifying a grey falcon while in the field. Schoenjahn (2010) has identified other species of birds which are often mistaken for a grey falcon such as the; brown falcon (Falco berigora), grey goshawk (Accipiter novaehollandiae), adult collared sparrowhawk (Accipiter cirrhocephalus), brown goshawk (Accipiter fasciatus) and the black-shouldered kite (Elanus axillaris).
Mainly grey upperparts and white underparts; darker on the tips of the flight feathers; yellow cere. Body length 30–45 cm; wingspan 85–95 cm; weight 350–600 g. Females larger. Grey falcons are known to have a body length between 30–45 cm, making them a mid-sized bird. Females are generally larger in body size and wingspan. The wingspan of a male is less than 300mm and the tail length is less than 150mm. For the females, the wingspan is generally more than 305mm and the tail length is more than 150mm. The weight of the grey falcon also fluctuates with gender. The female weighs approximately 559 grams on average (and between 486 and 624g) and the male is 378 grams (and between 335 and 419g). The grey falcon has mostly grey upper body parts. It is heavy-shouldered with a black streak under the eyes. The wingtips are also black and the cere, eye ring and feet are a very vibrant yellow. The tail of the bird is grey and faintly barred like the underwings. The lower section of the body is white with fine dark streaks and on younger birds this feature is darker and more distinctive. The call of the grey falcon is hoarse chattering, clucking and whining sounds. It is similar to the peregrine falcon and has a loud, slow ‘kek-kek-kek’ or ‘kak-ak-ak-ak’ but is slower, deeper and harsher than the peregrine falcon. 
Distribution and habitat
The grey falcon is an Australian endemic, usually confined to the arid inland. Open country: Triodia grassland, Acacia shrubland, and lightly timbered arid woodland. They have been sighted over most of mainland Australia except for Cape York. Very few have been seen on the Nullarbor Plain and in the Great Victoria, Gibson and Great Sandy Deserts. Most sightings of the grey falcon have been within the arid zones, with rainfall less than 500mm. When they have been occasionally seen outside of these areas, they have been found in similar dry, low altitude, open woodland or grassland. The only times this bird has been seen in different conditions has been along the Queensland coast during drought years. The grey falcon is often seen in family-type groups of an adult pair and usually one (but up to four) first year birds.
It is found at very low densities, numbering only 1,000 breeding pairs, and the population may be stable. Continued high levels of grazing in arid zone rangelands and clearance of the semi-arid zone for marginal farming is degrading habitat.
The species was previously listed as near-threatened; in 2012 it was uplisted to vulnerable. Listed on CITES Appendix II.
Grey falcon are listed as endangered on the Australian Environment Protection and Biodiversity Conservation Act 1999.
State of Victoria, Australia
- On the 2007 advisory list of threatened vertebrate fauna in Victoria, The grey falcon is listed as endangered.
State of Queensland, Australia
State of Western Australia, Australia
When sighted and observed, most grey falcons have been seen hunting. They have a habit of eating on the ground, in the open and around inland bores which make them quite easy to observe while eating. From 88% of observations it can be said that their main prey is other birds, followed by small mammals (6%), reptiles (5%) and insects such as worms (1%). The birds which they feed on usually form flocks and feed on the ground which is typical of birds in arid regions such as parrots and pigeons. Grey falcons have also been sighted with animals such as; a mallee ringneck, a duck, a yellow-rumped thornbill, locusts, snakes, a large dragon, the house mouse, rabbit kittens, lamb carcasses and one has even been seen pursuing a bat.
The grey falcon’s breeding range has shrunk recently with breeding occurring in the more arid sections of their distribution. They breed once a year but may nest twice a year during abundant seasons or may not nest during drought times. Breeding and nesting occur within the distribution range with nests normally being an abandoned stick nest from another species of bird of prey. Nests are often selected in an upright fork, of the top of a tall tree. These can be located in a patch or a belt of timber along a watercourse in dry inland areas. Nests can be used for several years within the nesting season of July to October in the south and April to June in the North. The grey falcon eggs look very similar to the black falcon’s (Falco subniger) but are slightly smaller. A clutch size is generally two or three and occasionally four eggs that are oval shaped and 51x38 mm on average.
- ^ BirdLife International (2012). "Falco hypoleucos". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
- ^ Watson, C. (2011). A failed breeding attempt by the Grey Falcon ‘Falco hypoleucos’ near Alice Springs, Northern Territory. Australian Field Ornithology, 28 (4), 167-179.
- ^ a b Schoenjahn, J. (2010). Field identification of the Grey Falcon ‘Falco hypoleucos’. Australian Field Ornithology, 27(2), 49-58.
- ^ a b c Marchant, S.; & Higgins, P.J. (Eds). (1993). Handbook of Australian, New Zealand and Antarctic Birds. Vol. 2: Raptors to Lapwings. Oxford University Press: Melbourne. ISBN 0-19-553069-1
- ^ Marchant, S.; & Higgins, P.J. (Eds). (1993). Handbook of Australian, New Zealand and Antarctic Birds. Vol. 2: Raptors to Lapwings. Oxford University Press: Melbourne. ISBN 0-19-553069-1
- ^ Schoenjahn, J. (2010). Morphometric data from recent specimens and live individuals of the Grey Falcon (Falco hypoleucos). Corella, 35(1), 16-22.
- ^ Simpson, K & Day, N. (2004). Field guide to the birds of Australia. Penguin Books –Viking.
- ^ a b c Olsen, P. D. (1986). Short communications - Distribution, status, movements and breeding of the Grey Falcon Falco hypoleucos. CSIRO, 47-51.
- ^ "Recently recategorised species". Birdlife International (2012). Retrieved 15 June 2012.
- ^ EPBC Act List of Threatened Fauna. environment.gov.au
- ^ Department of Sustainability and Environment, Victoria
- ^ Department of Sustainability and Environment, Victoria
- ^ Victorian Department of Sustainability and Environment (2007). Advisory List of Threatened Vertebrate Fauna in Victoria – 2007. East Melbourne, Victoria: Department of Sustainability and Environment. p. 15. ISBN 978-1-74208-039-0.
- ^ Queensland Department of Environment and Resource Management
- ^ Threatened Fauna Specially Protected Fauna Notice
- ^ Beruldsen, G. (2003). Australian birds, their nests and eggs. G. Beruldsen.