AUSTRALIAN 80 WATCHER

AUSTRALIAN BIRD WATCHER 1985, II , 80-91

The Black Falco subniger.· A Summary of Information and Comparison with the Falco berigora

By GREGORY V. CZECHURA, Queensland Museum, Gregory Terrace, Fortitude Valley, Queensland 4006 and STEPHEN J.S. DEBUS, P.O. Box 1015, Armidale, N.S.W. 2350

Summary The literature concerning field recogmhon, body weight, diet, feeding/hunting behaviour, courtship and breeding biology of the Falco subniger is reviewed and supplemented with field observations. Some comparisons are made with the Brown Falcon Falco berigora. Generally, the (larger) Black Falcon tends towards faster and more aerial hunting methods and avian prey, and the Brown Falcon tends towards slower and more stationary searching methods and terrestrial prey, with greater emphasis on reptiles. In bodily dimensions, hunting behaviour and diet, the Black Falcon resembles the Lanner Falcon Falco biarmicus and especially the Lagger Falcon Falco jugger rather than other Australian . In its adaptation to an arid environment (breeding strategy, diet and hunting tactics), the Black Falcon appears to differ somewhat from the Falco hypoleucos. Data on the biology of the Black Falcon are limited and require further investigation.

Introduction Calaby (1976) stated that not much is known about the habits of the Black Falcon Falco subniger, and claimed that confusion with dark-phase Brown Falcons Falco berigora has cast doubt on statements made about it. Cade (1982) implied that little is known about its hunting habits, breeding behaviour and nesting ecology. The purpose of this paper is to review what is known about the Black Falcon in order to identify some aspects of its behaviour and ecology that differentiate it from the Brown Falcon; also to draw together data scattered in the literature, and to place recent work (Cupper & Cupper 1981, Baker-Gabb 1984a, Hollands 1984) within the context of Cade's treatment of the genus Falco.

Field recognition The differences between the Black Falcon and the corvids on one hand, and the Brown Falcon on the other, have been exhaustively reviewed elsewhere (Olsen 1975, Pizzey 1980, Price-Jones 1983, Hollands 1984, Fraser 1985). Two points made by Olsen should be emphasised, viz. the kestrel-like flight action of Black Falcons and the 'step' in the outer edge of their tail tip resulting from the two outermost tail feathers being shorter than the rest. This latter feature is illustrated, but not mentioned, in Slater (1970) and is clearly shown in a photograph in Hollands (1984); it is visible only when the tail is fanned or partly so. As most observations tend to be made of in flight, some of the more useful identifying flight characteristics of the Black Falcon versus the Brown Falcon are summarised herein (Table 1, Figures 1 and 2). These characteristics are based on the above reviews, other guides (Condon 1966, Slater 1970, Storr & Johnstone 1979) and our own field observations. VOL. 11 (3) SEPTEMBER 1985 Black Falcon: Summary of Information 81

Table 1

Selected flight characteristics of Black Falcons Falco subniger and Brown Falcons Falco berigora

Characteristic Black Falcon Brown Falcon Wing tip Pointed (Figure la) Rounded (Figure 2a) 'Fingers' in wing tip Not obvious Usually obvious Tail Narrow and tapered Broad, no 'step'; usually when furled, giving rounded when soaring; streamlined appearance; appears tail-heavy squared when soaring, with 'step' Wing attitude when soaring Slightly drooped Upswept, with 'kink' or gliding (Figure 1 b) (Figure 2b,c) Trailing margin of wings Usually straight Usually curved when soaring (Figure Ia) (Figure 2a)

Figure 1. Diagrammatic view of Black Falcon Falco subniger: (a) flight silhouette; (b) wing attitude when gliding or soaring.

Figure 2. Diagrammatic view of Brown Falcon Falco berigora: (a) flight sillhouette; (b, c) wing attitude when gliding or soaring. Drawing by G.V. Czechura In flight, the Black Falcon is direct and has a stiff, 'flicking' action like a Falco peregrinus. Olsen (1975) noted that the wing tips are held down, thus forming an arc. In contrast, the flight of Brown Falcons is sometimes erratic, with much jinking and side-slipping during display. The flapping action of the Brown Falcon is of an overarm, 'rowing' type (Olsen 1975, Pizzey 1980). These differences are seen to best advantage during fast flights. Black Falcons at these times fly rapidly and directly with very quick wing beats. In contrast the fast flight of Brown Falcons, as when displaying or evicting intruders, becomes even more jerky and erratic: in particular, the downstroke becomes deeper and exaggerated, even being momentarily held at the bottom of the stroke (GVC pers. obs.). It should be noted that under some circumstances, both Black and Brown Falcons may assume similar or even reversed flight patterns. For example when not hunting, the Black Falcon's flapping action can be remarkably deep AUSTRALIAN 82 CZECHURA & DEBUS BIRD WATCHER and leisurely (McGilp 1934, Pizzey 1980), though not as laboured as a Brown Falcon's wing action (GVC and SD, pers. obs.). McGilp (1934) noted that the appearance of the Black Falcon in leisurely flight contrasts strongly with its speed and prowess when hunting. Reversal of the general trends of flight action is evident during display flights, when the Brown Falcon's wing beats can be quick and shallow (Baker-Gabb 1982, Appendix 1) and the Black Falcon's can be deep and slow (Hollands 1984). Such exceptions to the general rules on the flight actions of these two falcons could be sources of confusion for the unwary observer. Body Weight Baker-Gabb (1984b) gave the weight of female Black Falcons as 879-1000 g, averaging 940 g (n=2) and males as 620-710 g, averaging 664 g (n=5); a female in Hall (1974) weighed 843 g and Olsen & Olsen (1984) stated females to average close to 950 g. These data suggest that the 'females' in Brown & Amadon (1968) and Price-Jones (1983) that fall within the above range for males, may have been mis-sexed; one such 'female' from Price-Jones was actually a male (P. and J. Olsen in !itt.). Further examination of such anomalous specimens and data is warranted, since one would expect the Black Falcon to be as strongly sexually dimorphic in size as the other swift, largely bird-eating falcons (Newton 1979). Furthermore, in all observations of pairs in the field, pairs have always exhibited sexual dimorphism as great or greater than that of Brown Falcons (D. Baker-Gabb in !itt.). Using Baker-Gabb's morphometric data and the formula in Cade (1982, Table 4) the Black Falcon's wing loading is 0.38 glsq. em for males and 0.43 glsq. em for females, rather than Cade's figures of0.34 glsq. em for both sexes (based on an underestimate of body weights). This places the female Black Falcon in the heavily wing-loaded class of falcons (Olsen & Olsen 1984), especially since the formula slightly underestimates actual wing loading (Cade 1982). Though slightly heavier than the Peregrine Falcon, the Black Falcon has a lower wing loading and therefore greater manoeuvrability (Australian Peregrine: 0.50 and 0.57 g/sq. em, calculated as above). The Black Falcon is somewhat larger and considerably more heavily built than the Brown Falcon, with a higher wing loading (male Brown Falcons 417- 510 g, av. 474 g, females 560-730 g, av. 625 g, wing loading 0.34 and 0.37 g/sq. em; sources as above). Interestingly, the Black Falcon has a similar wing loading to Australia's other (smaller) desert falcon, the Grey Falcon Falco hypoleucos: male 0.30 g/sq. em, female 0.43 g/sq. em (Cade 1982, Czechura & Debus 1985). Diet The Black Falcon takes a variety of prey, including insects, reptiles, birds, mammals and carrion (Brown & Amadon 1968, Cupper & Cupper 1981 , Price-Jones 1983, Hollands 1984). This falcon frequently preys on birds, taking some up to the size of adult Pacific Black Ducks Anas superciliosa and Swamphens Porphyria porphyria (Bedggood 1979), 1059 g and 802 g respectively (Baker-Gabb 1982). McGilp (1934) recorded attacks on , pigeons, Cacatua roseicapilla and ducks. Hall (1974) recorded probable remains in stomach contents. Bennett (1 885) found that Little Button-quail Turnix velox and 'young' passerines such as a Richard's Pipit Anthus novaeseelandiae. songlarks Cinclorhamphus spp. and chats Ephthianura spp. were common prey, but he also recorded predation by this VOL. 11 (3) SEPTEMBER 1985 Black Falcon: Summary of Information 83

Black Falcon Falco subniger in flight Plate 20 Photo: David Hollands

Brown Falcon Falco berigora in flight Plate 21 Photo: Photo: J. & L. Cupper AUSTRALIAN 84 CZECHURA & DEBUS BIRD WATCHER

falcon on Letter-winged Kites Elanus scriptus. Quail occur frequently in the diet of Black Falcons in a number of areas (Berney 1905, Batey 1907, Cameron 1932, Shanks 1952, Austin 1953, Czechura 1971, 1979, Haddon 1976). Austin (1953) recorded -lark Grallina cyanoleuca and Common Skylark Alauda arvensis as prey. Rabbits Oryctolagus cuniculus, at least in the southern and central parts of Australia, form a prominent part of the Black Falcon's breeding diet (Cupper & Cupper 1981 , Baker-Gabb 1984a, Hollands 1984), thus confirming the general observations of Bennett (1885), McGilp (1934) and other naturalists. Unfortunately, the upper weight limit has apparently not been recorded for rabbits taken by Black Falcons; only immatures have been recorded as prey (Baker-Gabb 1984a). Rodents and other small mammals are also taken (Keartland in North 1912, Le Souef 1944, Cupper & Cupper 1981 , Price-Jones 1983, Hollands 1984) as are insects such as grasshoppers (Haddon 1976, Hollands 1984) and dragonflies (GVC pers. obs.). Though a smaller and more lightly built raptor (see above), the Brown Falcon does manage to take prey within the range and 'manner' of Black Falcons. Birds are sometimes taken in flight: Masked Lapwing Vanellus miles, Green Rosella Platycercus caledonicus, Sturnus vulgaris (Mooney 1981), Feral Pigeon Columba Iivia (Hunt 1982), Galah (Price-Jones 1983), Dollarbird Eurystomus orienta/is (Hughes & Hughes 1984) and Black­ faced Woodswallow Artamus cinereus (Hollands 1984). The heaviest prey recorded includes the Tasmanian Native-hen Gallinula mortierii (age not stated: Mooney 1981) and Eurasian Coot Fulica atra (Baker-Gabb 1984c), adults 1182-1350 g (Ridpath 1972) and 510 g (Baker-Gabb 1982) respectively; however Ridpath reported that Brown Falcons attacked young but not adult Native-hens. Rabbits up to 1 kg are taken (Cade 1982), and unsuccessful attacks are occasionally made on heavier mammals such as young hares Lepus capensis 2 kg-plus (Mooney 1981). Where Black and Brown Falcons breed sympatrically in arid Victoria, the Black Falcon's diet is 57% birds (mainly Galahs and Starlings), 40% rabbits, 2% mice and 1% insects, while the Brown Falcon's diet is 46% rabbits, 35% birds (mainly small passerines), 9% arthropods, 4% reptiles and 2% mice (Baker-Gabb 1984a). By contrast, the Brown Falcon's breeding diet in coastal Victoria is 15% rabbits, 25% rodents, 21% birds (mainly small passerines), 14% reptiles and amphibians (mainly the former) and 25% arthropods (Baker­ Gabb 1985). These findings indicate some similarity in the diets of the two , but suggest that some differences may exist in the proportions of the various prey classes taken (Black Falcon takes more and often larger birds, Brown Falcon takes more terrestrial prey). The introduction of the rabbit may have caused more dietary overlap than formerly existed. However, Olsen et al. (1979) reported 'numbers of birds' in the diet of some breeding Brown Falcons, and raised the possibility that Black Falcons obtain some of their avian food items by robbing Peregrines. The role of reptiles in the diets of the two species is also worthy of comment. It appears that reptiles do not figure highly in the Black Falcon's diet. The observations made by G.A. Keartland (in North 1912) for example, are suggestive of opportunistic predation. Kleptoparasitism mav nrovirh~ ;mnthf'r source of reptiles: near West Wyalong, New South Wales, GVC has observed a Black Falcon pursue a Little Eagle Hieraaetus morphnoides and rob it of a VOL. 11 (3) SEPTEMBER 1985 Black Falcon: Summary of Information 85 metre-long Eastern Brown Snake Pseudonaja textilis. In contrast, Brown Falcons take relatively more reptiles than do other sympatric raptors in southern Victoria (Baker-Gabb 1985) and may specialise on venomous snakes in some areas (Sonter & Debus 1985). Observations (Czechura 1971, pers. obs.) in south-eastern Queensland where a number of non-venomous snakes are common, indicate that these may be taken as well as venomous species and lizards (dragons and large skinks). Lea & Gray (1935) recorded a number of snakes and lizards (Egernia sp., Tiliqua sp., Ctenophorus sp.) in the diet of Brown Falcons, in addition to insects, seeds and bird fragments. Fyfe (1981) also recorded a number of lizards (dragon, monitor and large skink) and venomous snakes taken by Brown Falcons. Like the Black Falcon, the Brown Falcon sometimes eats carrion (Olsen et al. 1979, Mooney 1981, Hollands 1984, SD pers. obs.). Hunting and feeding behaviour When searching for prey the Black Falcon soars high on thermals, sometimes poising (Bennett 1885, Cameron 1932, McGilp 1934, Bedggood 1979, Fraser 1985, Robinson & Franklin 1985, GVC and SD, pers. obs.), quarters at 10-20 m (Price-Jones 1983, SD pers. obs.), or flies rapidly and directly at low levels (Bennett 1885, McGilp 1934, Bedggood 1979, Hollands 1984, GVC and SD, pers. obs.). Much searching appears to be done from high soaring flight with little flapping. Some searching (for mammals) is done from a prominent perch (Price-Jones 1983). McGilp (1934) claimed that the Black Falcon flushes prey from cover by screaming while flying at bushes, or by descending with flapping wings and much screaming. However, he clearly confused the courtship calls of some raptors with hunting behaviour, and screaming may also be in frustration at prey that has escaped (D. Baker-Gabb in litt.). It seems certain that Black Falcons do not 'typically utter loud screams' while chasing prey, as Cade (1982) claimed, and that this myth should be discarded (Olsen & Olsen 1984). The Black Falcon does flush prey from cover by means of a low pass (Czechura 1979) or by striking and hovering over foliage in which prey are hidden (Dawson 1972), but in our experience and that of Dawson it is a silent bird in the field. The Brown Falcon sometimes cackles when flushing prey from cover (Czechura 1979); misidentification could therefore be a further source of error in McGilp (1934). When attacking prey, the Black Falcon stoops from a height in Peregrine fashion (Bennett 1885, Haddon 1976, Morris 1976, Hollands 1984, Fraser 1985) or uses a short, shallow stoop and/or a direct chase (Bennett 1885, McGilp 1934, Haddon 1976, Price-Jones 1983, Hollands 1984, Robinson & Franklin 1985, GVC and SD, pers. obs.). It often uses a fast, low-level attack to surprise prey (McGilp 1934, Morris 1976, Bedggood 1979, GVC pers. obs.). It appears that a combination of such tactics is sometimes used: a stoop from a height to provide speed, and the final stages of the attack carried out in a more level approach. Ground prey such as mice (and presumably reptiles) are taken in a 'quick swoop' without landing (Le Souef 1944) or by pouncing (Hollands 1984), and young rabbits are taken on the run (McGilp 1934). Insects are taken from the ground or by aerial pursuit (Haddon 1976, Hollands 1984) or are snatched while soaring (GVC pers. obs.). Black Falcons may occasionally hover (Bedggood 1979, Dawson 1972). Co-operative hunting has been recorded, involving male and female with sharing of the AUSTRALIAN 86 CZECHURA & DEBUS BIRD WATCHER

Black Falcon Falco subniger with avian prey Plate 22 Photo: David Hollands catch (Bedggood 1979), several individuals chasing the same bird (Berney 1905), and both members of a pair hunting flocks of birds (McGilp 1934). Black Falcons make extensive use of other agents to flush prey, e.g. fires, stock, farm machinery, dogs, humans, other raptors (Bennett 1885, Berney 1905, Batey 1907, Cameron 1932, Shanks 1952, Haddon 1976, Czechura 1979, Price-Jones 1983, Hollands 1984, Fraser 1985, GVC and SD, pers. obs.). An interesting example of this behaviour has been observed near Lake Cowal, New South Wales (GVC and R.E. Czechura): a combined attack by an Australian Falco longipennis and a Black Falcon on a large, mixed flock of Red-rumped Parrots Psephotus haematonotus, Mallee Ringnecks Barnardius barnardi, Melopsittacus undulatus, Blue Bonnets Northiella haematogaster and Cockatiels Nymphicus hollandicus. The parrots were roosting or drinking when first attacked by the Hobby, which stooped at birds that were drinking. During the resultant confusion a lone Black Falcon attacked the scattering parrots from a rapid, low-level pass directed at those birds attempting to seek cover below bushes and trees. Black Falcons also frequently pirate prey (kleptoparasitism) from other raptors including Black-shouldered Kites Elanus notatus, Black Kites Milvus migrans, Little Eagles, Australian Hobbies, Australian Kestrels Falco cenchroides and Peregrines (Olsen et al. 1979, Percival 1984, Hollands 1984, GVC pers. obs.). Attacks by Black Falcons on concentrations/flocks of birds are usually conducted using a shallow stoop or direct pursuit (GVC pers. obs.). Large prey may be struck repeatedly rather than being struck and held by the Falcon (McGilp 1934). Most prey is plucked and eaten on a perch (McGilp 1934 ). but some feeding may occur (or commence) on the ground, e.g. insects. VOL. 11 (3) SEPTEMBER 1985 Black Falcon: Summary of Information 87 large prey and carrion (Bedggood 1979, Hollands 1984) or on the wing, e.g. insects and birds (McGilp 1934, Austin 1953, Haddon 1976, Hollands 1984). GVC has observed Black Falcons eating a Diamond Dove Geopelia cuneata and a Gibberbird Ashbyia lovensis on the wing near Coorabulka, western Queensland. During pursuit of prey, Black Falcons are agile and dashing (Bennett 1885, McGilp 1934) and may perform 'spectacular wing over-turns' (Haddon 1976) which are presumably a directional change involving a roll. In summary, using the terminology of Baker-Gabb (1980), the Black Falcon's hunting techniques include soaring and prospecting, transect hunting, fast contour hunting, high quartering, perch hunting, flushing from cover, ground hunting, mediated flushing and shadowing, and co-operative hunting. Attack techniques include stooping, direct flying attacks and tail chasing. Comparison with Brown Falcon hunting behaviour Brown Falcons also use many of the above hunting techniques, but are said to favour perch hunting (Cade 1982, Hollands 1984). In one study area with few perches, Baker-Gabb (1984c) found Brown Falcons to mainly use high quartering, hovering and perch hunting, followed in importance by ground hunting, fast contour hunting, low slow quartering, and soaring and prospecting. The Brown Falcon also employs mediated flushing, using agents such as fires (Cade 1982, Hollands 1984, GVC and SD, pers. obs.), stock (Haddon 1976), farm machinery (Campbell 1984) and occasionally shooters (Hall 1974) but apparently does not shadow other raptors. Brown Falcons occasionally attempt to flush prey from cover (Czechura 1979). Co-operative hunting (Mooney 1981, Campbell 1984) and kleptoparasitism (Cade 1982, Baker-Gabb 1984, Hollands 1984, GVC pers. obs.) have also been observed in this species. Brown Falcons use a glide or drop attack and are said to seldom stoop (Pizzey 1980, Price-Jones 1983, Hollands 1984). However, they do occasionally take flying birds in a stoop (Hunt 1982, Mooney 1984). One study in coastal Victoria (Baker-Gabb 1984c) found the hover and drop attack (on terrestrial prey) to be by far the most prevalent, with virtually no dive attacks or direct flying attacks; the few attacks on birds were glide attacks from a perch. Czechura (1971), using observations made largely in south-eastern Queens­ land, found that common hunting techniques included hovering, soaring and prospecting and perch hunting. Fast contour hunting is sometimes used (Hollands 1984, Baker-Gabb 1984c), presumably to surprise prey such as birds at close range. Young rabbits are taken this way (Price-Jones 1983). Tail chasing is commonly employed against birds once the prospective prey is in the air (Bennett 1885, McGilp 1934, Haddon 1976, Czechura 1979, Price-Jones 1983, Hollands 1984). One case (Czechura 1971) involved a Brown Falcon chasing passerines around a large fig tree Ficus sp. Brown Falcons can fl y swiftly when required and may take most of their avian prey in a tail chase, sometimes following them into cover (Mooney in Cade 1982); they also take nestlings of arboreally nesting birds (Morse 1922, Barnard 1925, Schrader 1974). In these respects they differ from the Black Falcon which apparently prefers to take its avian prey in full flight. Brown Falcons occasionally hunt flying insects from soaring flight, and consume them on the wing (SD pers. obs.). The Black Falcon is reported to spend much of its time in the air, whereas the Brown Falcon seldom flies far and spends much of the day perched (Cade AUSTRALIAN 88 CZECHURA & DEBUS BIRD WATCHER

1982, Hollands 1984). Indeed Bennett, writing as early as 1885, was impressed not only by the swift flight of the Black Falcon, but likened its endurance on the wing to a frigate bird Fregata. In general, the Black Falcon tends towards more high aerial searching methods and faster attack techniques to take much prey in the a'ir, while the Brown Falcon tends towards slower aerial or stationary searching methods to locate much prey on the ground although the actual attack may be fast. The Brown Falcon's long legs and terrestrial agility (Cade 1982) are consistent with its apparently greater reliance on ground hunting and terrestrial prey. Courtship and advertisement displays The Black Falcon's display consists of high soaring, and rapid mutual chases and stoops accompanied by screaming calls (Brown & Amadon 1968, Price-Jones 1983). Bedggood (1979) reported a male screaming and stooping at his mate, whereupon both side-slipped, called and flew to a tree together, perching side by side. Hollands (1984) reported a pair soaring high together; the male climbed with deep, slow wing strokes and then made a series of shallow passes over the female. Both gave short, clear, high-pitched, far­ carrying calls. Pizzey (1980) stated the species to give gull-like screeches in display flight. Apparent piracy of a male's prey by his mate (Le Souef 1944) may have included an element of courtship feeding, as was possibly the case with a pair observed by Cameron (1932) to 'dispute' possession of captured prey. Austin (1953) reported a pair making half-hearted attacks on each other in a 'playful fight' and calling with parrot-like notes usual for a falcon. We have not heard Black Falcons giving parrot-like calls, and other sources (e.g. Cupper & Cupper 1981, Hollands 1984) indicate that the Black Falcon's calls are more like a deep version of the Peregrine's call. It seems likely that Austin's observation is based on misidentified Brown Falcons. Breeding biology The Black Falcon's breeding biology has now been reasonably well outlined. Recorded breeding density varies from c. 1 pair per 1 500 ha or 1 pair per 4-5 km of watercourse in the Lake Eyre drainage system in good seasons (Blakers et al. 1984, Hollands 1984), down to 13 400 ha per pair in arid Victoria (Baker-Gabb 1984a). The incubation period is approximately 34 days (Cupper & Cupper 1981) and the nestling period is 38-42 days (Baker-Gabb 1984a). Pre-laying lethargy has been reported (Slater 1979).0nly the female has been recorded brooding the chicks and she usually feeds them; the male supplies the prey and sometimes feeds the chicks (Cupper & Cupper 1981, Hollands 1984). Prey presented to the young is usually plucked (Hollands 1984), although that presented to fledged young may be whole and unplucked or partly eaten (GVC pers. obs.) The chicks are brooded when downy, but the female ceases day brooding as they grow; they are nearly fully feathered at five weeks (Cupper & Cupper 1981). Both sexes often defend the nest vigorously but silently if the nest tree is climbed, in contrast to the Brown Falcon's noisy defence of the nest (Olsen & Olsen 1980, Cupper & Cupper 1981, SO pers. obs.). Details of the Black Falcon's breeding cycle resemble those of the better known falcons; long incubation and nestling periods are characteristic of the large falcons (Peregrine and 'great' falcons) rather than the medium-sized or small falcons (Cade 1982), and in these respects the Black Falcon resembles the former. VOL. 11 (3) SEPTEMBER 1985 Black Falcon: Summary of Information 89

The breeding distribution of the Black Falcon has been subject to some debate. Blakers et al. (1984) queried reports from the Kimberley region and Lake Way (Western Australia), but Keartland (in North 1912) clearly knew the bird (and the Brown Falcon) well. It would be premature to dismiss his records, since a female from the Kimberley region was starting to come into breeding condition in late May (Hall 1974). The Black Falcon probably penetrates some distance into Western Australia at higher latitudes as well: in January 1980, SD observed a number of juveniles and adult pairs in the Musgrave Ranges (north-western South Australia).

Discussion In body weight, wing loading, hunting behaviour and diet, the Black Falcon bears at least a superficial resemblance to the Lanner Falcon Falco biarmicus, and the two could be regarded as approximate ecological equivalents on different continents. The Lanner is the most aerial of the 'desert' or 'great' falcons; its diet is catholic but consists mainly of birds taken in a low-level surprise attack; it sometimes stoops, but less successfuly than the Peregrine (Cade 1982). In some aspects (shape, diet) the Black Falcon is even more like the Indian Lagger Falcon Falco jugger (J. Olsen pers. comm.). The Black Falcon also bears some resemblance (overall dark colouration, long wings and tail; dashing, aerial hunting behaviour) to two dry-country members of the hobby group: Eleonora's Falcon Falco eleonorae and Sooty Falcon Falco concolor. The Black Falcon's extensive use of thermals (Price-Jones 1983, Fraser 1985, Robinson & Franklin 1984, SD pers. obs.) and its apparent slowness when not hunting are probably energy-saving devices; its extensive use of tactics (e.g. mediated flushing) to secure prey may also minimise energy demands. It appears to have coped with the problems of survival in an arid environment in a somewhat different way from the Grey Falcon ( cf. Czechura & Debus 1985). The Black Falcon's rather high nesting density and fledgling productivity in the inland in good seasons (Hollands 1984), and apparent post-breeding dispersal coastwards (Fraser 1985), contrast with the Grey Falcon's apparently very low density. They also show some differences in diet and hunting behaviour: the Grey Falcon appears faster than the Black Falcon in hunting flight (Slater 1978), and in this respect resembles a small­ scale Peregrine; the Black Falcon exploits carrion but eats few reptiles, whereas the Grey Falcon includes some reptiles but not carrion in its diet; the Black Falcon appears to use a wider range of hunting techniques (kleptoparasitism, flushing from cover, almost all possible mediated-flushing agents). Futher investigation of these species in sympatry is clearlywarr~mted . The last point applies equally to the Black and Brown Falcons. Although these falcons also have some aspects of diet and hunting behaviour in common, important differences may exist in their non-breeding diets: the Brown Falcon's autumn and winter diet shifts to a lesser reliance on birds and a much greater reliance on rodents and arthropods, and its prey items are then very small relative to predator (Baker-Gabb 1984c); no such comparable data exist for the Black Falcon. Studies on their respective diets in the tropics, where there are no rabbits, would be valuable. From the limited data available on its aerial displays, it appears that the Black Falcon performs diving displays, aerobatics, exaggerated wing beats, AUSTRALIAN 90 CZECHURA & DEBUS BIRD WATCHER and mutual soaring and chasing displays common to many falcon species (Cade 1982). More observations are needed, but it seems that although similar in basic pattern there are some qualitative differences in the displays of the Black and Brown Falcons: the Brown Falcon apparently makes more use of low chases, side-slipping aerobatics and perching, and its calls are more raucous and crowing (Baker-Gabb 1982, Appendix 1). More data are needed on the Black Falcon's breeding biology, particularly on the roles of the sexes and development of the young. The Black Falcon's defence of the nest has been subject to some debate, but it is likely that the intensity of defence varies with several factors: the stage of the cycle (desertion may occur at the egg stage), any distress calls emitted by the young, habituation of the adults to the intruder (Olsen & Olsen 1980), and individual variation. Supposed desertion (e.g. Calaby 1976) apparently rests on a misinterpretation of Macgillivray (in North 1912). The relevant point for bird­ watchers, photographers and ornithologists is that their repeated presence may adversely affect the birds if the adults collide with branches or waste their energy while defending, or the young are exposed to predators or sun (Olsen & Olsen 1978). The Black Falcon has been alleged (e.g. Cade 1982), on inadequate evidence, to build its own stick nest but as with other falcons this is unlikely and is probably one of the myths that should be discarded. Our remarks on the Grey Falcon (Czechura & Debus 1985) apply: if falcons rely exclusively on the stick nests of other species, the availability of such nests could be an important limiting factor and source of interspecific competition. For conservation reasons this question should be settled by careful observation and documentation.

Acknowledgements We thank David Baker-Gabb and Penny and Jerry Olsen for their many valuable comments on an earlier draft of this paper. References Austin, C. (1953), 'The Black Falcon and some other raptors in south-western Victoria',Emu 53, 77-80. Batey, I. (1907), 'On fifteen thousand acres: its birdlife sixty years ago', Emu 7, 1-17. Baker-Gabb, D. (1980), 'Raptor Prey Record Scheme- an ARA project proposal', A"asian Raptor Assn News 1(4), 9-12. -- (1982), Comparative ecology and behaviour of Swamp Harriers Circus approximans, Spotted Harriers C. assimilis and other raptors in Australia and New Zealand, Ph.D. thesis, Monash University. - - (1984a), 'The breeding ecology of twelve species of diurnal raptor in north-western Victoria', Aust Wildlife Research 11, 145-160. -- (l984b), 'Morphometric data and dimorphism indices of some Australian raptors', Corella 8, 61-63. - - (l984c), 'The feeding ecology and behaviour of seven species of raptor overwintering in coastal Victoria', Aust Wildlife Research 11, 517-532. - - (1985), 'Accessory publication: "The feeding ecology and behaviour of seven species of raptor overwintering in coastal Victoria'", A'asian Raptor Assn News 6, 4-9. Barnard, C.A (1925), 'A review of the bird life on Coomooboolaroo Station, Duaringa district, Queensland, during the past fifty years', Emu 24, 252-265. Bedggood, G. (1979), 'Field notes on the Black Falcon', Aust. Bird Watcher 8, 31-34. Bennett, KH. (1885), 'Notes on the habits & C., of birds breeding in the interior of New South Wales', Proc. Linn. Soc. NS. W 10, 162-169. Berney, F.L. (1905), 'Field notes on the birds of the Richmond district, North Queensland', Emu 5, 15-20. Blakers, M .. Davies, S.JJ.F. & Reilly, P.N. (1984), The Atlas of Australian Birds, Melbourne University Press. Melbourne. VOL. 11 (3) SEPTEMBER 1985 Black Falcon: Summary of Information 91

Brown, L.H. & Amadon, D. (1968), Eagles, and Falcons of the World, Country Life, London. Cade, T.J. (1982), The Falcons of the World, Collins, London. Calaby, J. (1976), 'Black Falcon', in Reader's Digest Complete Book of Australian Birds, 133, Reader's Digest Services, Surry Hills. Cameron, AC. (1932), 'Birds at Quilpie, western Queensland', Emu 32, 104-105. Campbell, J. (1984), 'Apparent co-operative hunting by Brown Falcons', Aust. Bird Watcher 10, 205-206. Condon, H.T. (1966), Field Guide to the Hawks, BOC, Melbourne. Cupper, J. & Cupper, L. (1981), Hawks in Focus, Jaclin, Mildura. Czechura, G.V. (1971), 'Field notes on hunting methods of falcons', Sunbird 2, 68-72. -- (1979), 'Observations on quail-hunting strategies in some Australian raptors', Sun bird 10, 59-66. --· & Debus, S.J.S. (1985), 'The Grey Falcon Falco hypoleucos: a summary of information', Aust. Bird Watcher 11, 9-16. Dawson, P. (1972), 'Black Falcon at Carbrook', Sunbird 3, 14. Fraser, T. (1985), 'Notes on the Black Falcon Falco subniger in South Australia', Aust. Bird Watcher 11, 57-60. Fyfe, G. (1981), 'Predation on reptiles by the Brown Falcon (Falco berigora)', Herpetofauna 13, 31. Haddon, G. (1976), 'Black and Brown Falcons feeding ahead of moving sheep near Warren', Aust. Birds 11, 16-17. Hall, B.P. (Ed) (1974), Birds of the Harold Hall Australian Expeditions 1962-70, British Museum of Natural History, London. Hollands, D. (1984), Eagles, Hawks and Falcons of Australia, Nelson, Melbourne. Hughes, P. & Hughes, B. (1984), 'The raptors of Widgee', Sunbird 14, 37-40. Hunt, M. (1982), 'Brown Falcon hunting birds', A'asian Raptor Assn News 3(1), 14. Lea, AM. & Gray, J.T. (1935), 'The food of Australian birds', Emu 34, 275-292. Le Souef, AS. (1944), 'Black Falcon', Emu 43, 218. McGilp, J.N. (1934), 'The hawks of South Australia (Part 2)', S Aust. Om. 12, 26 1-293. Mooney, N. (1981), 'Some notes on the Brown Falcon in Tasmania', A'asian Raptor Assn News 2(4), 10. -- (1984), 'Brown Falcon takes rosella', A'asian Raptor Assn News 5, 33. Morris, F.T. (1976), Birds of Prey of Australia, A Field Guide, Lansdowne Melbourne. Morse, F.C. (1922), 'Birds of the Moree district', Emu 22, 24-38. Newton, I. (1979), Population Ecology of Raptors, Poyser, Berkhamsted. North, AJ. (1912), Nests and Eggs of Birds Found Breeding in Australia and Tasmania, Vol. 3, Australian Museum, Sydney. Olsen, G. (1975), 'The Black Falcon in the field', Canberra Bird Notes 3(2), 7-9. Olsen, J., Olsen, P. & Jolly, J. (1979), 'Observation of interspecific conflict in the Peregrine Falco peregrinus and other Australian falcons', Aust. Bird Watcher 8, 51 -57. Olsen, P. & Olsen, J. (1978), 'Alleviating the impact of human disturbance on the breeding Peregrine Falcon. !. Ornithologists', Corella 2, 1-7. -- &-- (1980), 'Observations on defence of the nest against humans by Australian species of Falco', Emu 80, 163-165. -- & -- (1984), Book review- The Falcons ofthe World Aust. Wildlife Reseach 11,205- 206. Percival, D. (1984), 'Black Falcon - poise and piracy', A 'asian Raptor Assn News 5, 45. Pizzey, G. (1980), A Field Guide to the Birds of Australia, Collins, Sydney. Price-Jones, H. (1983), Australian Bir_ds of Prey, Doubleday, Sydney. Ridpath, M.G. (1972), The Tasmanian native hen Tribonyx mortierii', parts I-III, CSIRO Wildlife Research 17, 1-118. Robinson, J. & Franklin, D. (1985), 'Feeding ecology of falcons', A 'asian Raptor Assn News 6, 10-12. Schrader, N.W. (1974), 'Ravens rescuing young bird', Aust. Bird Watcher 5, 204. Shanks, D. (1952), 'Hawks unusual to the south-west of Victoria', 52, 102-104. Slater, P. (1970), A Field Guide to Australian Birds. Non-Passerines, Rigby, Adelaide. - - (1978), Rare and Vanishing Australian Birds, Rigby, Adelaide. -- (1979), The Observer's Book of Birds of Australia, Methuen, Sydney. Sonter, C. & Debus, S.J.S. (1985), The Brown Falcon Falco berigora as a predator of snakes'. Aust. Bird Watcher 11, 92-93. Storr, G.M. & Johnstone, R.G. (1979), Field Guide to the Birds of Western Australia, Western Australian Museum, Perth. • VOL. 12 (1) MARCH 1987 Records of Birds from Christmas Island 7

Tree Sparrow Passer montanus* Several individuals have frequented the Flying Fish Cove cantilever area since at least March 1983 and possibly for two years beforehand (D. Powell pers. comm.). They are very timid but do not appear to be expanding their range on the Island. They were probably introduced accidentally by ship.

Acknowledgements We sincerely thank all of the Island residents who have reported unusual birds to us over the years, especially D. Powell, H . Yorkston, J. McMaster, J.N. Dunlop and Dr B. Reville. The following people and institutions kindly assisted with the identification of photographs and/or specimens: W. Longmore, W. Boles and T. Lindsey (The Australian Museum), Dr P.J. Fullagar and Dr R. Schodde (Australian National Wildlife Collection, CSIRO), R.E. Johnstone (Western Australian Museum), C. Corben, P. Grant and E.J. van Ijzendoorn.

References Andrews, C.W. (1900), A Monograph of Christmas Island (Indian Ocean), British Museum (Natural History), London. Bailey, R.S., Pocklington, R. & Willis, P.R. (1968) , 'Storm-petrels Oceanodroma spp. in the Indian Ocean', Ibis 110, 27-34. Gibson-Hill, C. A. (compiler) (1947), Papers by various authors on the natural history of Christmas Island in the Indian Ocean, Bull. Raffles Museum 11, 5-177. Gray, H.S. (1981), Christmas Island - Naturally, H.S. Gray, Geraldton, West. Aust. King, B., Woodcock, M. & Dickinson, E.C. (1975), A Field Guide to the Birds of South-East Asia, Collins, London. Mitchell, B.M. (1974), 'The forest flora of Christmas Island', C'wealth For. Rev. 53, 19-29. Pocklington, R. (1979), 'An oceanographic interpretation of seabird distributions in the Indian Ocean', Marine Biology 51, 9-29. Robinson, H.C. & Chasen, F.N. (1936), The Birds of the Malay Peninsula, vol. 3, Witherby, London. Seebohm, H. (1890) , The Birds of the Japanese Empire, Porter, London. Serventy, D.L., Serventy, V. & Warham, J. (1971), The Handbook ofAustralian Seabirds, Reed, Sydney. Van Tets, G.F. (1974), List of bird species found at Christmas Island, in Conservation of Endangered Species on Christmas Island: A Report of the House of Representatives Standing Committee on the Environment and Conservation, Aust. Govt Pub!. Serv., Canberra. - - (1978a), 'Transmarine dispersal of Black Cormorants', A'asian Seabird Group News!. 10, 21-24. - - (1978b), 'Transmarine dispersal of Australian Pelicans', A 'asian Seabird Group News!. 11, 5-6. --(1983), List of bird species found at Christmas Island, Annex E in The Preservation of Abbott's Booby on Christmas Island, Report of the Senate Standing Committee on Science, Technology and the Environment, Aust. Govt Pub!. Serv., Canberra. •

Corrigenda- Yo!. 11 no. 3 'The Black Falcon Falco subniger: a summary of information and comparison with the Brown Falcon Falco berigora': in the discussion of display vocalisations (p. 88), Austin's report of Black Falcon calls should read 'parrot-like notes unusual for a falcon'.

Vol. 11 no. 4 'Parental care and investment in the Tooth-billed Bowerbird Scenopoeetes dentirostris (Ptilonorhynchidae)' : in the discussion of nest and nestling defence (p. 112), the quoted figure for Green Catbird nesting success rate should have been 65%, not 75%. This does not affect the conclusions regarding breeding systems in the catbirds versus bowerbirds.