VOL. 18 (7) SEPTEMBER 2000 267 AUSTRALIAN WATCHER 2000, 18, 267-269 Observations on the Grey Falco hypoleucos

by ROD HARRISON, P.O. Box 42, Bribie Island, Queensland 4507

The following observations on the Grey Falcon Falco hypoleucos derive from random sightings over many years in various parts of inland and northern Australia. They are intended to supplement the information in Marchant & Higgins (1993), as summarised by Debus (1998). Some statements in the earlier literature, on the Grey Falcon's general habits, speed, and perceived rarity, are debatable.

Distribution and status I have observed Grey , as single , pairs, or adults with fledglings, on the shores of Exmouth Gulf (W.A.; 22°00'S, 114°20'E), at Rabbit Flat (N.T.; 20°16'S, 130°04'E), Coober Pedy (S.A.; 28°56'S, 134°45'E), Kimba (S.A.; 33°08'S, 136°23'E), the Paroo River near Wanaaring (N.S.W.; 29°43'S, 144°10'E), Lake Julius on the Leichhardt River north-east of Mt Isa (Qld; 20°10'S, 139°43'E, where I also observed a Red Goshawk Erythrotriorchis radiatus), Kynuna (Qld; 21°35'S, 141°55'E), and the Channel Country of western Queensland. The fledglings were on the Georgina River west of Boulia (Qld) in September, indicating an early laying date of July, or perhaps June, from incubation and nestling periods of over a month each for this species (Marchant & Higgins 1993). Over many years to 1999, in the Channel Country, I was engaged in the control of pigs and other feral during the winter months on properties between Windorah, Bedourie and Boulia. On every trip I saw at least one Grey Falcon. An area where Grey Falcons were frequently sighted, as singles or pairs, was a section of the Barcoo River (a branch of Cooper Creek) north of Windorah. Black Falcons Falco subniger were noticeable in the region during some winters, but in wet years seemed to be absent. This pattern suggests that Black Falcons are the more migratory or nomadic.

A third record for New Guinea In addition to the two published records of the Grey Falcon for the savannas of southern New Guinea (Marchant & Higgins 1993), I observed a Grey Falcon on the Bensbach River floodplain, near the Papua New Guinea/lrian Jaya border, in April 1992. The bird was perched in a tree on the river bank, and allowed a close approach (within 20 m) by boat before flying off on powerful pointed wings. The habitat of the area was mainly river floodplains and savanna.

Behaviour and flight characteristics My first sighting of a Grey Falcon was of a bird flushed from a fence-line by a vehicle near Wanaaring in inland New South Wales. Once airborne, the Falcon seemed unconcerned at the vehicle and flew close to the ground, as if using the fence to dampen a strong winter wind blowing across the plain. Before our courses diverged, its half-closed wings thrust it along with rounded wing-strokes at a speed matching that of the vehicle. This flight pattern was similar to that of long­ winged terns Stema beating into the wind. AUSTRALIAN 268 HARRISON BIRD WATCHER

Grey Falcon soaring Plate 75 Photo: David Hollands Grey Falcons observed included birds that were perched in trees, or standing on the ground where there were trees nearby. Others were soaring, hunting, or courting. Perhaps more so than any other Australian raptor, the Grey Falcon exhibits a variety of flight characteristics. In windy and open areas Grey Falcons sometimes fly low, less than a metre above the ground, into the wind. Exaggerated wing-beats and wings held high, like those of a Black-shouldered Kite Elanus axillaris as it descends from a hover, also form part of an extensive aerial repertoire. The latter behaviour, which is energy-inefficient flight, has been observed only between members of a pair of Grey Falcons, and is presumed to be courtship. The flight patterns of soaring and hunting birds are different again. Where there are no rising thermal currents, Grey Falcons soar on flat wings interspersed with deep wing-beats. Birds seen hunting at low level also hold their wings flat, giving the impression that only the tips are working. This behaviour may be to minimise movement, so as not to alert the birds on which the Falcon feeds. When in direct pursuit of prey, Grey Falcons seem to develop deeper, more thrusting wing-beats. Grey Falcons tend to be visible only at specific times of the day, such as early and late when hunting, when travelling to an overnight roost, or when soaring while the thermals are rising. Unlike the opportunist raptors, which prefer vantage perches and thus frequently present silhouettes for bird-watchers, Grey Falcons spend many daylight hours resting amongst the branches of leafy trees. They are secretive, hiding in the dense parts of Coolibahs Eucalyptus microtheca where mobbing birds such as miners Manorina and Magpie-larks Grallina cyanoleuca do not find them readily. On several occasions I was alerted to the presence of a perched Grey Falcon by the calls of mobbing birds. I also found that, when walking along watercourses 'driving' pigs and discharging firearms, I sometimes flushed Grey Falcons from the trees.

Hunting I have not observed any hunting behaviour by the Grey Falcon other than the VOL. 18 (7) SEPTEMBER 2000 Observations on Grey Falcon 269 pursuit of birds: most frequently Crested Pigeons Ocyphaps lophotes, Richard's Pipits Anthus novaeseelandiae, Budgerigars Melopsittacus undulatus, other small parrots, and honeyeaters (Meliphagidae) . Some were taken at the end of extremely fast dives, and others in direct flight after being surprised feeding on the ground. The Falco peregrinus appears to be marginally faster than the Grey Falcon in a dive. However, both Grey and Black Falcons can be just as quick, if not faster, in sustained level flight, and have superior soaring capabilities.

Discussion My observations suggest that, although uncommon, the Grey Falcon is not as rare as is generally believed. Its perceived rarity and threatened status should be tempered by the fact that the Falcons are often cryptic, and tend to make themselves visible only at certain times. A true assessment of the species' would necessitate appropriate survey techniques such as walking along inland wooded watercourses, and perhaps flushing birds from cover by means of real or simulated gunshots at regular intervals. It appears that the Grey Falcon is most numerous in the Channel Country of western Queensland. As long as this region is not overgrazed, or converted to irrigated cotton-farming by appropriation of the waters of Cooper Creek, those Coolibah-lined waterways are likely to remain the Falcon's stronghold. My record supports the view that Grey Falcons are occasional, perhaps 'overshooting', non-breeding vagrants or migrants to southern New Guinea. Their occurrence there would require a sea crossing of over 100 km across Torres Strait, unless the birds 'island hop' en route for distances of tens to 50 km between landfalls. Grey Falcons seem to be extremely economical flyers: fast when the occasion demands, but generally using the wind or atmospheric conditions exceptionally well. In this respect they resemble the , which behaves similarly. My observations on the Grey Falcon concur with the observations of Slater (1997) and with the information in Marchant & Higgins (1993) and Debus (1998), but conflict with some of the earlier, erroneous or biased literature used by Cade (1982) to characterise the species. As confirmed by other recent research (Marchant & Higgins 1993, Debus & Rose 2000), Grey Falcons clearly use rapid flight to prey predominantly on birds.

Acknowledgement I thank Stephen Garnett for reviewing a draft.

References Cade, T.J. (1982), The Falcons of the World, Collins, London. Debus, S. (1998), The Birds of Prey of Australia, A Field Guide, Oxford University Press, Melbourne. Debus, S.J.S. & Rose, AB. (2000), 'Diet of Grey Falcons Falco hypoleucos breeding extralimitally in New South Wales', Aust. Bird Watcher 18, 280-281. Marchant, S. & Higgins, P.J. (Eds) (1993), Handbook of Australian, New Zealand and Antarctic Birds, vol. 2, Oxford University Press, Melbourne. Slater, P. (1997), Australian Birds, Parish, Brisbane. Received 20 April 2000 •