SPECIES

Black Falcon Falco subniger Scientific name definitions

Stephen Debus
Version: 2.0 — Published March 17, 2023

Diet and Foraging

Introduction

Black Falcon takes a range of vertebrate prey (mammals, birds, reptiles) from rodents and small passerines to mammals up to ca. 500 g and birds up to ca. 1 kg, though mostly in the range 50–400 g; it sometimes also takes large insects, e.g., beetles (Coleoptera), dragonflies (Odonata), and grasshoppers or locusts (Orthoptera) (1, 3). Mammals taken include young European rabbits (Oryctolagus cuniculus). Birds commonly include quails (Coturnix and Synoicus), pigeons, parrots, and passerines, but can include ducks, small herons, smaller raptors, cockatoos (Cacatuidae), and crows (Corvus). Reptiles taken include skinks (Scincidae) and small monitor lizards (Varanus); snakes are occasionally robbed from other raptors, and a rare record of a freshwater turtle (Chelidae) may have been robbed from a kite (Haliastur). It occasionally scavenges, although adults do not bring carrion to the nest. Across its range, this falcon’s diet is broad, varying geographically and focusing on the locally most abundant or available prey. In the temperate south, it mostly takes birds, and in the arid zone, some native mammals (rats, Rattus) as well, when they are abundant. It rarely attacks domestic poultry. Most dietary data are from breeding adults in temperate and tropical southeastern and eastern Australia, with few studies in the arid zone and tropical far north. There is little information on the diet and foraging of immature falcons, from during the nonbreeding season, or for non-territorial falcons in the breeding season. The mostly anecdotal collated records (1, 3) suggest a similar diet to that of breeding falcons (see Diet in this section), although probably with a greater emphasis on flying insects in the warmer months and perhaps on kleptoparasitism and carrion.

Feeding

Main Foods Taken

The Black Falcon’s diet is diverse. Throughout Australia, it preys mainly on birds, some mammals, a few lizards, and some flying insects, with the proportions varying according to geographic region and major biome. It sometimes scavenges on road-killed vertebrates in the same size range as captured prey or somewhat larger (e.g., adult rabbits) and more rarely on larger dead mammals (1, 3). For details, see Diet in this section.

Microhabitat for Foraging

Most avian prey are taken in the air, often flushed from the ground or the tree or shrub canopy, and mammals and reptiles are taken from the ground; insects are taken in flight and sometimes from the ground (1, 3). For details of the broad habitat types used for foraging, see Habitat.

Food Capture and Consumption

Black Falcon is a versatile, opportunistic, and primarily aerial hunter, spending much time on the wing (42, 45, 21, 39, 1, 22, 46, 3). It searches for prey by soaring, high quartering (circling at ~50 m) or transect flights (direct coursing at medium height), fast contour-hugging flight (low to the ground, often following a drainage channel or other watercourse), or perch-hunting, and it attacks prey in a direct flying attack, stoop (at aerial prey), tail-chase (extended close pursuit of flying prey), or dive to the ground (47, 48, 49, 45, 21, 39, 50, 17, 51, 52, 53, 7, 54, 55, 38, 43, 56, 57, 8, 9, 44, 10, 19). A stoop sometimes flattens out near ground level to become a low, fast pass to flush prey or snatch a small item from the ground or water without landing (58, 45, 59, 21, 46, 43, 8, 9, 19). Some birds are taken in a surprise attack from low flight over the treetops or from behind cover (e.g., hillocks, farm buildings, irrigation channel banks, dikes) (48, 21, 22, 60, 5, 38, 44, 19), and cooperative hunting by members of a pair is common, with tandem hunts initiated by either sex (48, 45, 61, 62, 63, 64, 22, 54, 38, 65, 8, 66, 9, 67, 19). Some tail-chases can be prolonged, covering up to at least 400 m (39, 17, 53, 19). Dependent juveniles sometimes accompany their hunting parent(s) (9). In the arid zone, it hunts birds at waterholes and wetlands (45, 68, 21, 1, 69, 55, 70). It will hawk flying insects in soaring flight with shallow stoops (59, 71, 45, 39, 1, 17, 7, 38, 8, 72, 9, 19), catch locusts and crickets (Orthoptera) by running on the ground, and scrabble about on the ground for a bird that has escaped into vegetation (73, 45). Small prey, such as insects and sometimes small passerines and mice, are eaten in soaring flight (74, 59, 71, 45, 21, 39, 50, 46, 17, 5). One falcon, after 45 min of hunting Australian Magpie (Gymnorhina tibicen), stooped and caught one among several that had been mobbing the falcon (75).

Black Falcon makes much use of tactics to facilitate the detection and capture of prey, e.g., flushing prey from cover, and mediated flushing by following agents such as farm machinery, vehicles, livestock, Emu (Dromaius novaehollandiae), other animals, or human hunters, such as shadowing other foraging raptors like harriers Circus spp., and by attending grass fires, stubble burns, shooters, and irrigation flooding of fields (47, 58, 76, 74, 77, 78, 59, 45, 21, 39, 61, 62, 63, 50, 64, 1, 46, 17, 52, 5, 79, 8, 80, 81, 10, 3). It also robs other raptors, corvids, and sometimes conspecifics of prey (76, 82, 83, 68, 21, 39, 61, 63, 50, 84, 1, 22, 46, 17, 85, 86, 19, 87, 88, 3); one female even robbed her mate (58), and members of another pair catching quail "always disputed their prey for some minutes" (47). Some attacks on smaller raptors may be predatory in intent (e.g., Black-shouldered Kite (Elanus axillaris), Nankeen Kestrel (Falco cenchroides)) (39, 89, 90, 88). It also "shepherds" or chivvies high-swirling flocks of Galah (Eolophus roseicapilla) or Rock Pigeon (Columba livia), keeping the flock in the air until one breaks away and the falcon can stoop at it (22, 17, 65, 8).

Despite historical claims to the contrary, Black Falcon is typically silent when hunting (and indeed most of the time except during breeding activities), and it generally does not vocalize when attacking or attempting to flush prey (21, 17, 43). Most such claims probably originated with a misidentified Brown Falcon (Falco berigora), which is much more vocal. In the accounts by Bedggood (48) of foraging Black Falcons, some claims of vocalizing seem convincing, but some of the described pair interactions may have involved elements of courtship or food-begging. There are also no convincing or reliable reports of a Black Falcon hovering kestrel-style on beating wings; the few historical claims possibly involve a misidentified Brown Falcon or inaccurate use of the term "hover" (e.g., for slow circling or "kiting" on stationary wings) (91). However, Black Falcon does occasionally hover briefly and clumsily in front of foliage when trying to flush prey that has taken refuge in a tree (92), when searching the outflow shoreline of a dam wall, or when searching for ground prey among grass tussocks (48). Sometimes, one member of a cooperatively hunting pair will land and clamber along branches in an attempt to flush prey for its mate waiting in the air (57).

There have been no detailed studies of hunting success in Black Falcon, but in a cumulative sample of 35 incidentally observed attacks on vertebrate prey (almost all birds), nine (26%) were successful (3). However, it is difficult to distinguish genuine attempted strikes from exploratory passes, feints aimed at flushing prey, or identifying and singling out a vulnerable individual. Five of 14 attacks (36%) by breeding adult falcons on avian prey succeeded (19). Three of eight attacks (38%) by falcons on quail succeeded (49). One falcon pair, hunting quail flushed by a moving mob of sheep over several days, caught "numbers" of quail daily, and "practically never missed" (47). One pair of falcons spent over an hour at a wetland, chasing flocks of potential prey species many times, before the female finally caught a small shorebird (70). Two Black Falcons hunting a flock of thousands of Budgerigar (Melopsittacus undulatus) coming to drink at a waterhole each took 5 or 6 stoops to make a capture, and one falcon hunting a tightly swirling flock of Rock Pigeon took ~5 stoops to capture one (55). One falcon made 11 stoops at a flushed Australian Pipit (Anthus australis) that dodged, "ringing up," before both were lost to view (76). Black Falcon has difficulty penetrating a swirling, coordinated flock of European Starling (Sturnus vulgaris) or shorebirds, but can easily catch a panicked starling that separates from the roosting flock or a shorebird separate from the main flock (93, 17, 60). One falcon had 20–30 dives at an immobile immature rabbit, finally brushing its head, whereupon the rabbit leapt up and then escaped down a burrow (50).

Diet

Major Food Items

Avian prey are from a wide range of orders and species, mostly quails and buttonquails, pigeons/doves, parrots, and passerines < 400 g, but can extend to mid-sized waterbirds up to ~1 kg (ducks, wading birds), corvids, small cockatoos (< 500 g), and even occasionally other (smaller/lighter) raptors, e.g., Elanus kites and Nankeen Kestrel (Falco cenchroides) (1, 3). Birds taken are mainly flocking species that feed on the ground in the open.

Mammalian prey in the temperate to arid southeast are typically immature rabbits and introduced rodents (Mus, Rattus). Prey on the subtropical east coast are introduced rats (Rattus), with one observation of a falcon hawking insectivorous bats (Microchiroptera) at dusk, although most mammals taken are terrestrial species. Mammals taken in the central and northern arid zone include young rabbits (where available) and native rodents (Rattus). Those taken on the tropical coasts include native and introduced rats (Rattus spp.) and other native rodents (Melomys sp.), and a terrestrial marsupial (bandicoot, Isoodon sp.) (1, 3).

The few records of reptilian prey involve skinks, a small monitor lizard (Varanus sp.), an anomalous record of a freshwater turtle (possibly robbed from an aquatic kite, Haliastur sp.), and snakes robbed from a Little Eagle (Hieraaetus morphnoides) and a Brown Falcon (21, 61, 3).

Black Falcon sometimes scavenges on a range of mammals, including road-killed rabbits, foxes, and kangaroos or wallabies (Macropus spp.), and even a short-beaked echidna (Tachyglossus aculeatus) (94, 45, 39, 50, 95, 1, 96, 3). They may also scavenge on road-killed or injured birds (48, 19), and occasionally on road-killed reptiles (61). They are audacious, able to displace most other raptors from a carcass (22).

Various casual observations in the southeastern agricultural belt, from the post-breeding season to the pre-breeding season (i.e., early summer to autumn) (58, 76, 74, 73, 59, 71, 45, 39, 7, 38, 72, 19; SJSD), suggest that more flying insects are taken during the warmer months, but otherwise its foraging behavior and prey profile are similar to those in the nesting season. Adults, particularly males, may catch many flying insects when away from the nest during the nesting season (7, 8, 9).

Major Prey by Region

Reviews (1, 3) reveal that the relative importance of prey taxa varies by ecoregion. In the southeastern agricultural belt, the principal prey in the nesting season are birds, particularly pigeons (the feral Rock Pigeon (Columba livia) and Crested Pigeon (Ocyphaps lophotes)), Galah (Eolophus roseicapilla) and other parrots, and European Starling (Sturnus vulgaris) (7, 5, 38, 9, 10, 19).

In the southeastern arid zone, the principal prey in the nesting season were immature rabbits, Galahs, and European Starlings (97). Other records for the central arid zone suggest that rabbits and native rats (Rattus) can be important when abundant (98, 45, 99), although rabbit remains may persist longer than other remains below falcon nests, so their importance may be overestimated. In the northern arid zone, the main prey were buttonquails (Turnix), passerines, and native rats (100).

On the subtropical east coast, the principal prey in the nesting season are quails (Synoicus), ducklings, pigeons and doves, waterbirds (e.g., Eastern Cattle Egret (Bubulcus coromandus)), small cockatoos (e.g., Little Corella (Cacatua sanguinea)) and other parrots, and Common Myna (Acridotheres tristis) (9). On the tropical east coast, the principal prey in the nesting season are terrestrial native and introduced rodents and waterbirds (11). On the tropical northern floodplains, the principal prey in the nesting season are native rats (Rattus sp.) (33).

Quantitative Analysis

Most dietary studies have been conducted at nests. Studies at nests have analyzed prey by a combination of orts (remains), pellets, and direct observation, taking care not to double-count the same individual item from these various sources, and not assuming that one pellet equals one prey individual, in order to minimize biases and maximize the detection of prey species (7, 11). Such caution is applied because the adult(s) can share a large prey item with the nestling(s), and a large prey item may provide more than one meal for a parent and young, and hence a single prey item can appear in more than one pellet. Conversely, some items may appear in orts but not pellets and vice versa (9). Thus, calculation of the minimum number of individuals (MNI) represented by body parts (e.g., skulls, paired jaws or other bones, teeth, claws, flight feathers) per batch of samples (by site and date) is used to quantify the diet.

Two meta-analyses summarized the diet in 11 nesting-season studies in eight areas of Australia, mainly in the southeastern temperate zone and subtropical and tropical eastern coastal zones (1, 3). These revealed that in the southeastern temperate zone, the breeding diet consists, by number or frequency, mostly of birds (55–98%) and some mammals (rodents or young rabbits, 2–4%), with insects (up to 41%) in varying proportions, although birds dominate by biomass (91%), while insects contribute little (< 1% of dietary biomass). Other, less detailed studies in the temperate zone found a similar breeding diet consisting mainly of birds, with some mammals, an occasional lizard, and insects. In somewhat drier parts of the agricultural zone, among mostly avian prey, the Galah, a small cockatoo, provides ~40% of vertebrate prey by number. In the southern arid zone, before the calicivirus (rabbit hemorrhagic disease) decimated the introduced rabbit population, birds dominated by number (57%), although mammals (42%, mostly immature rabbits) dominated by biomass (60%). On the subtropical east coast where prey were abundant, the breeding diet consisted of 100% birds in the incubation and nestling periods and 59% birds and 41% mammals by number (~50% each by biomass) in the post-fledging period. The switch to rats in the post-fledging period coincided with crop harvesting that left rats exposed and vulnerable. On the tropical Queensland coast, the breeding diet consisted of mammals (63% by number, ~67% by biomass) and birds (37%, ~33% by biomass), with some insect remains in pellets. On the tropical Northern Territory coastal floodplains, the breeding diet consisted of mammals (74% by number), birds (20%), reptiles (4%), and insects (2%).

There are few quantified estimates of predation. In the southeastern arid zone, a Black Falcon pair and their four young were estimated to consume ~130 immature rabbits in four months of the breeding season (97).

Food Selection and Storage

Black Falcon takes live vertebrate prey in the range of 10–1,000 g, but mostly between 50 and 400 g (21, 1, 7, 5, 9, 10, 3). It eats or partly eats larger prey at kill sites and brings the remainder (e.g., headless body or hindquarters, often plucked) to the nest or transports whole smaller prey (e.g., birds) to the nest (45, 21, 7, 8, 10). It sometimes brings more food than the chick(s) can eat in a single meal, so excess prey is stored in cache sites near the nest, typically tree hollows but also sometimes on the ground at the base of a tree (9, 19). Both members of a pair cached prey in the earth bank of a farm dam during winter (13).

Foraging Response to Change in Prey Availability

Black Falcon has taken to including in its diet many introduced birds and mammals, which have become available only in the preceding century or two and which now dominate or form a substantial part of the falcon's diet in the southeastern agricultural zone (see Diet: Major Food Items). These invasive species are abundant agricultural and urban pests.

Data suggest that the relative proportions of birds and mammals in the falcon's diet vary with local or regional availability (see Major Food Items and Major Prey by Region in Diet)

Nutrition and Energetics

In the temperate southeastern agricultural belt, male prey delivery rates to pre-laying and incubating females were 0.14–0.29 items per h (~11–19 g/h), and 0.09–0.15 items per h (~4–9 g/h), respectively (19). The parental prey-delivery rate was 0.3 items per h (~50 g of prey biomass per h) to nestlings and 0.4 items per h (~70 g/h) to fledglings in the southeastern agricultural belt; on the subtropical coast, prey-deliver rates were 0.7 items per h (~70 g of prey biomass per h) to nestlings and 0.5–0.6 items per h (~80 g/h) to fledglings on the subtropical coast; in the latter case, the rate declined through the post-fledging period to 0.2 items per h towards juvenile independence (7, 9). Prey appeared more abundant at the coastal site, enabling the use of caching throughout the breeding cycle and facilitating a larger brood size (four fledglings), whereas caching was not used at the inland site and brood reduction occurred (three chicks, two fledglings). In bad weather in the agricultural belt, feeding rates and biomass provision were low at a nest that failed during the hatchling phase (0.26 items per h, ~28 g/h, most of it consumed by the adult female), and low to a single nestling that fledged underweight (0.19 items per h, ~23 g/hour) (19).

In its foraging adaptations and strategies, the falcon seems geared to maximizing the finding and capture of prey in open environments with low and erratic rainfall and frequent lean times. The versatile foraging ecology, e.g., its broad dietary spectrum and ability to switch prey types according to availability and its use of caching and occasional scavenging, are evidently adaptations to take advantage of whatever food is available in a potentially or seasonally harsh environment. Nevertheless, Black Falcon is very energetic in pursuit of prey and piracy victims, expending much energy in vigorous flapping flight of sometimes long duration (see Feeding: Food Capture and Consumption).

Metabolism and Temperature Regulation

No detailed information. Black Falcon is apparently more tolerant of heat and direct sunlight than is Peregrine Falcon (22, 17, 5). Brooding females sometimes sun-bask on an exposed perch near the nest, facing the rising sun with belly feathers fluffed, on cold mornings (7), and dependent juveniles sometimes sun-bask on exposed perches (9).

Drinking, Pellet-Casting, and Defecation

One report of drinking, on the subtropical (high-rainfall) coast: a breeding male drank from a pool of water on a road before going to roost (9). Black Falcon is less dependent on the presence of surface water than is Peregrine Falcon in inland Australia (22).

During the nesting season, pellets accumulate below nests. Pellets are typically compact bundles of fur or feathers, sometimes enclosing teeth, claws, bird bills or feet, or fragments of insect exoskeletons (7, 38). Pellet samples from northern inland New South Wales measured 19–55 × 13–27 mm (mean 37 × 20 mm, n = 33), and 31–40 × 15–23 mm (mean 35 × 19 mm, n = 7) and weighed 1.3–2.7 g (mean 2.2 g, n = 8). Those from the subtropical northern coast of New South Wales measured 24–69 × 15–23 mm (mean 39 × 19 mm) and weighed 0.7–3.4 g (mean 1.0 g, n = 10). Those from southern Victoria measured 37–49 × 19–28 mm (n = 2) and weighed 1.7–4.3 g (mean 2.9 g, n = 4). Those from the tropical Northern Territory measured 18–57 × 14–28 mm (mean 33 × 21 mm) and averaged 2.2 g (n = 54). Those from the tropical east coast of Queensland measured 26–69 mm × 11–31 mm (mean 42 × 20 mm) and weighed 0.7–4.5 g (mean 2.1 g) (7, 9, 33, 10, 19, 11).

Recommended Citation

Debus, S. (2023). Black Falcon (Falco subniger), version 2.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.blafal1.02