Observation on Interspecific Conflict in The
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VOL. 8 (2) JUNE, 1979 Interspecific Conflict in Peregrine 51 Observation on Interspecific Conflict in the Peregrine Falco peregrinus and other Australian Falcons By JERRY OLSEN, Goswood, Sutton, New South Wales, 2581, PENNY OLSEN, Division of Wildlife Research, CSIRO, P.O. Box 84, Lyneham, A.C.T., 2602, and JEFF JOLLY, 3 Puckridge Place, Port Lincoln, South Australia, 5606 Introduction Interspecific conflict was observed on a number of occasions during an investigation into the breeding biology and diet of the Peregrine Falcon in parts of S.A. and N.S. W. These anecdotes and some similar obser vations on other Australian falcons are discussed. Interspecific Conflict in the Peregrine Falcon 1. Conflict with Congeners: Peregrines commonly interact aggresively with medium and large-sized falcons in other areas of the world. Cade (1960) for example, noted that 'Next to eagles, peregrines are most ready to attack gyrfalcons' (p. 200) . Ogden (1972) and Nelson (1969) describe Peregrines in aerial combat with Prairie Falcons Falco mexicanus at nest sites. Only one example of conflict with congeners was observed in our study areas during breeding. A pair of nesting Brown Falcons F. berigora repeatedly attacked a female Peregrine near Port Lincoln, South Austra li a, and eventually drove it away. However Brown Falcons nested at th e base of one Peregrine nest site and were frequently seen near other sites but no conflict was observed in our presence. Walsh (1978) did see Pere grines attack Brown Falcons although they were not consistent in their attacks. Australian Kestrels Falco cenchroides nest near most Peregrine nest sites in the Canberra area and on the same cliff face, within thirty metres of nesting Peregrines, at three sites. No conflict has been observed and Kestrels at this latter three sites have been seen to ring up in flight with the Peregrines disturbed by us. The Peregrines watchd by Walsh (1978) also ignored Kestrels. However, we found the remains of a Kestrel amongst the food debris at one of the sites where Peregrines and Kestrels both nested on the same cliff and the four eggs laid by the Kestrels were deserted. European Kestrels Falco tinnunculus nest on cliffs with Pere grines in Switzerland (Herren, 1959). Ratcliffe (1973) recorded a Pere grine in Britain that took over, hatched and raised a brood of Kestrels in a nest on the same cliff after its own eggs apparently failed due to pesticides. No other Australian falcons have been found nesting on cliffs. All Black Falcon Falco subniger nests we have visited were on wide fi ats or plains some distance from the hills used by the Peregrines in one of our study areas. Although these Black Falcons were competing directly with the Peregrines for food in this area, no conflict was seen. We have witnessed conflict away from nest sites, particularly in areas where Peregrines and Black Falcons move out onto fiat farmland. For example, between November and March numbers of both species including immature Peregrines can be seen on plains near Adelaide. Black Falcons, which approximate Peregrines in weight but are larger in dimensions, often rob or chase Peregrines in this area (for example, Robinson, 1976), resembling Sakers Falco cherrug in this respect (Mavrogordato, 1966). AUSTRALIAN 52 OLSEN, OLSEN & JOLLY BIRD WATCHER A 'battle' was seen between a Black Falcon and a Peregrine over Port Lincoln in which the Black Falcon was easily outflown. Davis (1965) has observed an Australian Hobby Falco longipennis har rassing a Peregrine, however we haven't seen this species in conflict with another raptor. 2. Conflict with Eagles: Conflict with eagles of the genus Aquila is common over much of the Peregrine's world range. Cade (1960) notes " . Peregrines are quickest and most persistent in their attacks on the Golden Eagle Aquila chrysaetos in Northern Alaska" (p. 200). Brown (1955) describes an instance in Kenya where a pair of Verreauxs Eagles Aquila verreauxi were forced to move their nest site because of attacks by a pair of Peregrines. Rat cliffe (1962) found evidence that Golden Eagles displaced Peregrines in Britain and Ferguson-Lees (1951) pointed out that these Peregrines and eagles are never found occupying the same cliff. Walsh in Australia (1978) stated "In the early stages the Peregrines were very aggressive, particularly towards the Wedge-tailed Eagles; they would stoop at them at an unbelieveable speed as well as attack from below ... " (p. 140) . Other similar anecdotes in the Australian literature include Hitchcock and Jarman (1944), and Reilly (1975). We have observed conflict between Peregrines and eagles on a number of occasions. A male Peregrine attacked four Wedge-tailed Eagles flying on a hillside 150 metres from his eyrie in the Canberra area. The falcon forced all four eagles to the ground, with repeated stoops, and held them down while we approached to within fifty metres of them. At an eyrie in the Port Augusta area both adults attacked a passing Wedge-tailed Eagle but the eagle rolled onto its back presenting its talons. This was done at each attack, consequently the falcons were not as effective as in the previous example. A similar encounter was observed near Carnarvon, Western Australia (Brooker, pers. comm.). It is interesting that we observed a male Peregrine perform the same rolling tactic at its eyrie to deter a Willy Wagtail Rhipidura leucophrys mobbing it. Wedge-tailed Eagles nest in the vicinty of Peregrine eyries in all of our study areas and some of the falcons are dependent on them for nest sites. Peregrines in the Port Lincoln area use large stick nests, placed on high sea cliffs overlooking the Southern Ocean, which we assumed were built by White-bellied Sea Eagles Haliaeetus leucogaster until we found Wedge tailed Eagles nesting on these cliffs. This species has not been recorded as cliff nesting, however, it is difficult to determine whether the Wedge-tailed Eagles constructed the nest. Eagles of the genus Haliaeetus may conflict with Peregrines as often as Aquilas. Bald Eagles Haliaeetus leucocephalus are constantly harrassed by Peregrines in the Queen Charlotte Islands, British Columbia (Beebe, 1960) , and Nelson (1973) has analysed these attacks in his ethological studies. Cade (1960) notes "It appears to be difficult for a Golden Eagle to flip and present its feet to an attacker from above" (p. 200). Bald Eagles frequently roll as do Wedge-tailed Eagles. White-bellied Sea Eagles nest near Peregrines in two of our study areas. They are also capable of rolling although we have witnessed no conflict. The literature contains a few accounts of Peregrines attacking these eagles (North, 1912; Fleay, 1948) and of the eagles rolling in defense (Chaffer, 1944). VOL. 8 (2) JUNE, 1979 Interspecific Conflict in Peregrine 53 3. Conflict with Other Raptors: The male Peregrine that forced four Wedge-tailed Eagles down was also seen to stoop near vertically at great speed at an adult female Brown Goshawk Accipiter fasciatus, which avoided the falcon by diving for cover. This male ignored the Brown Falcons we saw at nearly every visit to this eyrie. A juvenile Brown Goshawk was found dead of unknown causes near Peregrine eyrie. Walsh's (1978) Peregrines ignored Brown Goshawks nesting nearby but attacked Brown Falcons. Clunie (1976) reported an instance of the Fiji Peregrine attacking the Fiji Goshawk Accipiter rufitorques, a similar bird to the Brown Goshawk. Other raptors encountered near eyries were Whisting Kites Haliastur sphenurus, Little Eagles Hieraeetus morphnoides, Ospreys Pandion hali aeetus, Collared Sprarrowhawks Accipiter cirrhocephalus and Black shouldered Kites Elanus notatus; none were seen to be attacked. McCulloch (1975) has observed a Peregrine chasing a Harrier Circus sp. while Hindwood (1933) saw a Swamp Harrier and Peregrine in conflict over a dead pigeon. Favaloro (1942) observed Peregrines driving off a Whistling Kite from its nest, later nesting in it, and Storr (1964) reported a Peregrine chasing a Little Eagle. One site in the Canberra area, where the resident pair of Peregrines has not bred for four years, has had pairs of nesting Coll ared Sparrowhawks, Brown Falcons, Brown Goshawks and Little Eagles in the fo ur hectares surrounding the cliff. Frequent visits are made to the area by Wedge-tailed Eagles and Whistling Kites. Very high desities of rabbits possi bl es account for the number of raptors at this site. No interactions with Peregrines have been noted, however it is possible that the rabbits attract so many raptors that these Peregrines are constantly disturbed and consequently do not breed. 4. Conflict with Other Animals At two eyries in central New South Wales foxes were found under cliffs, one dead and one alive with a broken back. The dear fox had a slash in its back possibly caused by a Peregrine and both may have been dislodged from the top of the cliff by falcons. At four eyries in gorges over rivers Great Cormorant Phalacrocorax carbo, Wood Ducks Chenonetta jubata and Pacific Black Ducks Anas superciliosa have been seen flying down the river about ten to twenty metres above the water until they approached the nest cliff at which point they dipped and flew just above the water. These duck species are used as food (e.g. Barnard, 1925) and cormorants are often attacked by Peregrines (e.g. Bridgewater, 1933; Bright, 1935). A female Peregrine defending her nest (three eggs) from us was attacked by an Australian Magpie Gymnorhina tibicen and driven to the base of her own cliff. She made no effort to defend herself. A Peregrine has been seen to drop a newly caught Galah Cacatua roseicapilla when harried by Magpies (D' Andria, 1969) and Sutton (1935) records a Pere grine eating a Magpie. Chandler (1972) reports two Currawongs Strepera sp.