VOL. 18 (8) DECEMBER 2000 313 AUSTRALIAN WATCHER 2000, 18, 313-319

Postures, Displays and Copulation of the Pied Strepera graculina

by K.A. WOOD, 7 Eastern Avenue, Mangerton, N.S.W. 2500

Summary Postures and displays of the Pied Currawong Strepera graculina were recorded during 223 hours of observation at seven nests in Wollongong, New South Wales, between 1993 and 2000. The threat posture involved gazing from a horizontal stance to deter or expel avian intruders from the defended territory. Both sexes advertised their breeding status by drooping the wings and cocking the tail. The food-begging display was given only by the female. She quivered her wings and begged vocally when seeking food from the male. The solicitation or flirting disrlay was given by the male and the female, either singly or simultaneously. It involved wmg­ quivering without an exchange of food, often while the body was slightly crouched. A single intra-pair and a single extra-pair copulation were observed.

Introduction Many workers have discussed the function of visual and auditory signals in the courtship of . These courtship signals may serve to select a breeding partner (Welty 1988), advertise a breeding territory (Jansen 1999), regulate the timing of sexual readiness (Lack 1968) or strengthen the relationship of the bonded pair (Armstrong 1965). Displays performed in courtship range from the elaborate ritual of the Tooth-billed Bowerbird Scenopoeetes dentirostris (Frith & Frith 1993) to the rather demure pre-copulatory behaviour of Horsfield's Bronze- Chrysococcyx basalis (Tarburton 1993) and the Fan-tailed Cuckoo Cacomantis flabelliformis (Smedley 1983). In the Pied Currawong Strepera graculina, Recher (1976) described courtship and copulation of a breeding pair at Dangar Island, New South Wales. Prawiradilaga (1996) summarised copulation behaviour at Canberra during a three-year study. In this paper, I report some postures and displays observed at Wollongong, New South Wales, over the last seven years. I also describe the only intra-pair and the only extra-pair copulation that I observed.

Methods Observations were conducted at seven nests in various breeding stages between 1993 and 2000. Six nests were in suburban Wollongong and one was in the Illawarra Coast Range. At these seven nests, I performed 121 contmuous watches, mostly of more than one hour on different days, accumulating 223 hours of direct observation. In addition, a total of 71 brief inspections was made, typically of 10 to 20 minutes' duration. Information presented in this paper was a~uired by using 8 x 40 binoculars and a camera with a 500 mm lens. Detailed notes were entered m field diaries. Four of the nests were the subject of a previous paper in which the sexing criteria of individual breeding birds were described (Wood 1998). Some parent birds were colour-marked. All times are Eastern Standard Time.

Results Two postures were observed, each performed by the male and female. Of the two displays that were recorded, the food-begging display was used only by the female whereas the solicitation or flirting display was used by both sexes. These AUS'IRALIAN 314 WOOD BIRD WATCHER

postures and displays were seen mostly at distances less than 50 m from the nest. One intra-pair and one extra-pair copulation were also observed.

Threat posture While perched, the Currawong adopts a somewhat horizontal stance with outstretched neck and bill (Figure la). Wings are held closely against the body. The bodyline occasionally dips below horizontal, with the head held lower than the tail. Eyes gaze at the offending individual, enhancing the brightness of the yellow irides. Sometimes the bill points towards the offending individual. In the breeding season, the purpose of the pose is to drive unwanted birds from the proximity of the nest. Accordingly, this stance and gaze are directed towards conspecific individuals, brood-parasites such as Channel-billed Scythrops novaehollandiae and nest-predators such as Australian Ravens Corvus coronoides. Less frequently, I have also seen this pose in the non-breeding season, with the threat directed at roosting Southern Boobooks Ninox novaeseelandiae or Brown Goshawks Accipiter f asciatus perched or in flight.

Breeding-advertisement posture This posture is used in the breeding season, immediately upon landing. The Currawong adopts a normal stance but droops both wings and often cocks its tail (Figure lb). The pose is held typically for 30--60 seconds. The purpose of this pose is to advertise breeding status. Such advertisement would strengthen the pair-bond and also make conspecific individuals aware that a nest is nearby. occasionally cock their tails upon landing in the non-breeding season, but rarely (if ever) droop their wings at the same time.

Food-begging display The female begs vocally like a juvenile Currawong while the male is in view. If she approaches him for food, she partly spreads her wings (until left and right outer primaries are approximately parallel) and quivers them horizontally 6-8 times in quick succession while begging. Sometimes her tail is cocked. If the male feeds her, she sometimes utters a 'satisfied squawk' reminiscent of a juvenile bird when fed by a parent. The food-begging and wing-quivering display is performed to satisfy the female's hunger and maintain the pair-bond. It is often referred to as courtship­ feeding.

Solicitation or flirting display A Currawong of either sex adopts a slightly crouched stance and quivers both wings horizontally while looking at the other Currawong. This display is similar to the food-begging display of the female, but no begging call is uttered, and there is no overt suggestion of food being delivered by the male or wanted by the female. Sometimes the neck is extended and the bill pointed upwards. Occasionally the tail is wagged horizontally. VOL.18 (8) Postures, Displays and Copulation DECEMBER 2000 of the Pied Currawong 315

(a)

(b)

Figure 1. Postures of the Pied Currawong, traced from photographs: (a) threat, (b) breeding advertisement. Crouched wing-quivering is used to display sexual readiness and maintain the pair-bond. Mostly only one of the bonded partners performs the display while the other is in sight, up to 50 m away. Mutual solicitation occurs less frequently.

Extra-pair copulation The extra-pair copulation was seen at the suburb of Mt St Thomas, where the breeding pair had been watched previously for a total of 9.5 hours while they built their first nest. This nest was destroyed in gale-force winds on 31 October 1996 just before incubation commenced. Seven days later, they began to construct a second nest in the same tree, about 7 m from the first; nest-building was watched for a total of 19 hours over 11 days before incubation commenced on 20 September. On 22 September, the watch commenced at 0824 h. At 0857 h, 0933 h and 0939 h, the male fed the female while she was incubating the . At 1050 h, while the breeding female was incubating, I saw copulation between the breeding male and another female. The relevant extract from my field diary is repeated below; M = breeding male, F = breeding female. AUSTRALIAN 316 WOOD BIRD WATCHER

1018 h F re-commenced incubation. 1022 h M arrived back at the nest-tree, landed c. 8 m below the nest while F was incubating, and began preening. 1032 h M flew c. 2 m to a slightly higher branch and gave a mild flirtation display while looking northwards. 1033 h M flew c. 65. m northwards and landed about 80 cm from another Currawong near the top of a eucalypt tree. F still incubating. M and the other Currawong engaged in mutual solicitation; 3 wing-quivering sequences by M in 20-30 seconds, two sequences by the other Currawong. While incubating, F uttered a single cu"ah note, either during or shortly after the mutual solicitation sequences in her view 65 m away. 1034 h Other Currawong 'dropped' down into suburban garden and out of my sight, but M stayed perched near the top of the eucalypt tree until at least 1046 h. 1050 h M arrived back near the nest and within a minute flew to ground c. 10 m south and captured a Bogong MothAgrotis infusa. M flew back into tree adjacent to the nest-tree with the moth in his bill and looked northward again. Gained elevation towards his partner in the nest by a series of short hops and flights within 20-30 seconds [as usual when about to courtship-feed the Fon the nest]. When M was c. 3 m below nest, he looked northwards and again saw another Currawong perched in the eucalypt tree 65 m away. Almost immediately he flew northwards and landed in the eucalypt tree about 50 cm from the other bird. Upon landing, mutual solicitation occurred again, M fed the moth to the other Currawong and mounted her. Their cloacae were engaged for about three seconds while M was wing-flapping to maintain balance. 1052 h M and the other female Currawong 'dropped' down into suburban garden and out of my sight. F checked, still incubating. 1053 h F left nest and landed on a branch in the nest-tree c. 4 m away. Stayed there for 10-15 seconds then flew northwards across the road towards the eucalypt tree. Landed in a dead tree next to the eucalypt tree in which the extra-pair copulation was seen. The event described was an extra-pair copulation because I simultaneously saw the breeding female incubating eggs and the breeding male in coition with another Currawong. The breeding male was the partner of the incubating female because his attachment to her had been previously established during continuous observation since 0824 h. He was about to courtship-feed her on the nest, as he had done three times previously since 0824 h, when he flew about 65 m northwards and copulated with another female.

Intra-pair copulation The second nest at Mt St Thomas failed when it was raided by Channel-billed Cuckoos at approximately 0300 h on 17 October 1996. Two six-day-old Pied Currawongs and a Channel-billed Cuckoo nestling were found on the ground underneath this nest on 20 October. The breeding pair made yet another attempt to breed this season in the established territory by constructing a third nest, 35 m from the second in an adjacent Spotted Gum Corymbia maculata. I watched for a total of 12.5 hours over the 13 days from the commencement of the third nest on 20 October to its completion on 1 November. On 4 November, before VOL.18 (8) Postures, Displays and Copulation DECEMBER 2000 of the Pied Currawong 317

incubation commenced, I saw copulation of the breeding pair. The relevant extract from my field diary is repeated below. 0719 h F was perched 15 m high on the northern edge of the nest-tree where she had been for the last 18 minutes. M was in trees c. 100 m east. 0720 h M arrived back in the nest-tree, landing at nest height (c. 12 m) on the northern edge of the tree c. 7 m from the nest and c. 3 m below the female. As soon as he landed, she 'dropped' down through the tree foliage, gliding over the riest and landing on a branch c. 2 m below it. As she flew down, the male gave a flirting display (3-4 bouts of 5-7 wing-quivers each). 0721 h When F landed on the branch below the nest, she adopted the crouched solicitation stance but with her head tilted backwards and bill pointed at about 40 degrees above horizontal. Simultaneously, she peered at her partner 7 m away and bobbed her tail vertically in about 8-10 bouts. I have not seen vertical tail­ bobbing before. The bobbing amplitude was variable but occasionally exaggerated. The 8-10 bouts of tail-bobbing occupied about 90 seconds while M looked at F. He was perched in the solicitation pose, with head held normally but with his body feathers somewhat ruffled. 0723 h M flew towards F and landed c. 25 cm away on the same branch facing her. The male (but not the female) immediately commenced quivering outstretched wings and at the same time the breeding partners touched each other's bill tips in a manner reminiscent of fencers in an epee contest (could also be interpreted as 'kissing'). Their bills touched maybe 12 or 14 times then she cocked her tail, exposing her vascular cloaca and he mounted her. While balancing on her dorsum, he lowered his tail and their cloacae were engaged for a few seconds. At approximately 0724 h, the male dismounted, flying to a slightly lower branch c. 3 m away and calling currah-currah-currong in flight. At the same time, the female flew up to the nest and began to rearrange some of the twigs that had been previously put into position.

Discussion The postures and displays described in this paper supplement knowledge of the breeding behaviour of the Pied Currawong. Neither the threat posture nor the breeding-advertisement posture has been described previously. The food-begging display, however, was similar to that performed at Dangar Island (Recher 1976). Moreover, there were many similarities between the solicitation displays at Wollongong, Dangar Island (Recher 1976) and Canberra (Prawiradilaga 1996). Wing-flicking solicitation displays are common in some Australian robins (see Brooker & Saffer 1996), the malurid fairy-wrens (Rowley & Russell 1997) and the Australian (Schodde & Tidemann 1986). In songbirds, not all wing-quivering displays lead to copulation. Indeed, in 42 hours of watching the Currawong pair at Mt St Thomas in the nest-building phase, I saw many solicitations and courtship-feeding events but only a single intra-pair and a single extra-pair copulation. Recher (1976) observed copulation of the Currawong pair at Dangar Island 'fewer than twelve times'. Conversely, at some 38 nests, Prawiradilaga (1996) saw eight intra-pair copulations in three years, a copulation rate that seems closer to that at Wollongong than at Dangar Island. Among the , Rowley (1973) saw copulation of the Australian Raven only once in seven years, and Birkhead et al. (1987) believed that Eurasian AUSTRALIAN 318 WOOD BIRD WATCHER

Table 1 Elements of pre-copulation in the Pied Currawong. M =male, F =female, Y =seen, N = not seen, n m = not mentioned. Present study Present study Recher Prawiradilaga (intra-pair) (extra-pair) (1976) (1996) Solicitation F

Magpies Pica pica probably mated about three times per clutch (of about six eggs). Near Armidale, N.S.W., Tremont & Ford (2000) saw only eight intra-pair copulations of Leaden Flycatchers Myiagra rubecula in 661 hours of observation of 12 breeding pairs. There were notable differences and similarities in pre-copulatory behaviour at Wollongong, Canberra and Dangar Island. Of six elements that were recognised (Table 1), tail movement by the female occurred at all three locations. Only at Wollongong did the male puff up his body feathers and feed the female immediately before coition. Only at Wollongong did the female point her bill skywards, bob her tail vertically and expose her vent. These latter pre-copulatory elements have sometimes been noted for female Australian Magpies Gymnorhina tibicen in Western (Wilson 1946, Robinson 1956) and New Zealand (Brown & Veltman 1987). Courtship-feeding just before coition also occurs in Rooks Cmvus frugilegus in the Northern Hemisphere (Welty 1988). Recent studies using DNA fingerprinting have shown that extra-pair matings in birds are more common than previously thought (Mulder et al. 1994). Not surprisingly, field observations of these copulations are few (Ford 1983, Neill & Lill 1998). The extra-pair and intra-pair copulations seen at Wollongong occurred in a matter of seconds, a finding in common with copulation duration times of Currawongs at Canberra (Prawiradilaga 1996) and the Black-billed Magpie Pica pica hudsonia in North America (Birkhead 1991 ). In the extra-pair mating at Wollongong, the preliminary display contained fewer elements than the display before the intra-pair copulation (Table 1). The breeding male at Wollongong apparently simply seized a moment of opportunity to mate with a philandering female. In Sheffield, England, Birkhead (1991) described an extra-pair mating of the Eurasian Magpie: the male copulated with another attached female when her male escort momentarily fell asleep. In both of these instances, males, rather than females, seized an opportunistic moment to mate with another bird of the opposite sex. VOL. 18 (8) Postures, Displays and Copulation DECEMBER 2000 of the Pied Currawong 319

This study has shown that Pied Currawongs use a range of visual signals in the breeding season. The role of the sexes in courtship seems as diverse as the signals themselves. Further studies would provide additional information about the secret lives of breeding Currawongs.

Acknowledgements I thank Ian Rowley, Stephen Debus and an anonymous referee for commenting on the manuscript, and Julia Hurley for diligent editing.

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