VOL. 18 (7) SEPTEMBER 2000 259 AUSTRALIAN WATCHER 2000, 18, 259-266 Notes on Feeding Habits of the Pied Strepera graculina at Wollongong, New South Wales

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

Summary Data on the feeding habits of Pied Strepera graculina were acquired from incidental observations between 1984 and 1996 and 175 hours of continuous watches at five nests. Of 483 insects captured, 245 (51%) were taken on the ground, 212 (44%) were taken from trees or shrubs and 26 (5%) were caught in the air. Most insects (60%) were captured by gleaning. Diet in winter consisted almost entirely of fruit. Pied Currawongs rarely used their feet to handle food, and their attacks on live avian prey were based on surprise mostly from the rear. Surplus food was either abandoned or retrieved within 24 hours of capture.

Introduction The Strepera graculina is generally referred to as an (Hall 1907, Rowley 1990) that forages on the ground and in trees and shrubs (Debus 1996). Many articles have been published about foraging, but quantitative information about the range of foraging methods is lacking. This paper supplements knowledge about the feeding habits of Pied Currawongs, based on observations at Wollongong, New South Wales, over the last 13 years.

Study area and methods

Opportunistic observations Incidental observations of behaviour of Pied Currawongs were documented by the author while residing at Mangerton (34°26'S, 150°52'E), a suburb of Wollongong. There are records for every year from 1984 to 1996 (total = 159, range four in 1984 to 31 in 1993). Each record includes the date, number of seen together, food eaten, feeding behaviour or any aspect of the ' biology that was considered significant. All sightings were at Mangerton or adjacent suburbs.

Studies at nests Continuous watches, mostly greater than one hour, were made at five nests as follows: 1. Mangerton, nest in a public reserve dominated by wet sclerophyll forest and surrounded by well-vegetated suburban gardens; 29 hours (cumulative) during the nestling phase in 11 watches from 28 October to 12 November 1993. 2. Coniston, nest in a light commercial area surrounded by well-vegetated suburban gardens and playing fields; 6 hours during the incubation phase in two watches on the day before the nestlings hatched (13 November 1993). During the nestling phase, 63 hours during 36 watches from hatching on 14 November to fledging on 21 December. 3. Mt Keira, nest in wet sclerophyll forest with partly burnt understorey; 20 hours during the incubation phase in 16 watches from 17 October to 3 November 1994. 4. Mt St Thomas, nest in a residential area with well-vegetated suburban gardens and some vacant allotments; 10 hours during the nest-building phase in six watches from 23 to 30 August 1996. 5. Mt St Thomas, a second (replacement) nest built in the same tree as nest 4 presumably by the same pair after nest 4 was destroyed by gale-force winds on 31 October 1996 (before laying commenced); 39 hours during the nest-building and incubation phase in 27 watches from 1 September to 10 October 1996. During the nestling phase, 8 hours during three watches on 12 and 13 October. Continuous watches were made, mostly from ground level, with either binoculars or a AUSTRALIAN 260 WOOD BIRD WATCHER

17x Kowa telescope at distances of less than 70 m. Some birds were colour-marked, and sexing criteria were given by Wood (1998).

Analysis offoraging for insects Foraging terms generally follow those described by Ford et al. (1986). Turms used are glean: a perched or walking bird captures visible prey from a substrate; snatch: a flying bird snatches prey from foliage or bark; hawk: a flr·ng bird catches a flying insect; tear: a perched or walking bird tears, prizes or moves part o the substrate to reveal and capture prey; and probe: a perched bird inserts its bill into the substrate to extract concealed prey. A single foraging event is defined as one bird performing one successful prey attack.

Results

Foraging for insects Of 483 instances when Currawongs were seen to capture insects, 279 (58%) were by breeding birds near their nests. The remaining 204 instances (42 % ) were by birds of unknown breeding status at other locations: 86 in the breeding season (September-March) and 118 in other months. All foraging methods were used, but most insect prey (60%) was taken by gleaning (Figure 1). Hawking was performed least (5% of instances) and occurred mostly during the civil twilight after sunset. Tearing and probing occurred predominantly in the non-breeding months (97% by these methods), whereas 96 percent of gleaning, snatching and hawking events occurred in the breeding season. No insects were seen hunted in June or July. Fifty-one percent of insects were captured on the ground, 44 percent were taken from trees or shrubs, and five percent were caught in the air. While foraging on the ground, Pied Currawongs used saltatory searching for insects (see O'Brien et al. 1990). They stopped to look and listen before probing or prizing for prey. Occasionally, a bird turned its head sideways and lowered it towards the ground, to either listen or search more intently for prey in the substrate. The birds sometimes removed small clumps of lawn or leaf-litter by digging with the bill before capturing the prey. In one instance, I examined a native cockroach Panesthia, after the bird captured it by carefully looking and listening under dead Casuarina needles then digging it up from 50 mm below the surface. When Currawongs foraged on lawns, the median distance between search sites was six Currawong steps or about 80 cm (range 2-13 steps, n = 38). Visual acuity was remarkable. At the Mt St Thomas nest, parent birds took insect prey on the ground, after gliding directly to it from perches up to 40 m away. Small insects were often captured in long or short grass after the birds flew directly to the prey from a perch 20-30 m away.

Foraging for fruit, seeds and nectar Large flocks of 100-200 birds congregated at native and introduced trees in winter (see Wood 1998, Table 5). These large flocks comprised Currawongs feeding on the fruit (30-40% of flock) and cohorts in adjacent non-fruiting trees, either digesting fruit or about to fly into the fruiting tree. The largest trees held large crops of fruit. Quadrat sampling in winter 1995 indicated that the largest Lilly Pilly Acmena smithii and Moreton Bay Fig trees each held over 100 000 fruits. In 1996, the largest Lilly Pilly tree provided a source of cdihle fruit from 21 June to 20 August. Visitation rates at fruiting trees, however, VOL. 18 (7) Feeding habits of SEPTEMBER 2000 Pied Currawong, N.S.W 261

n = 483

probe Figure 1. Proportional use of insect-foraging methods by Pied Currawongs at hawk 60% Wollongong, N.S.W., glean 1984-1996.

were highly variable and large numbers of birds were often noted feeding on the fruit on particular days and much smaller numbers on the day before or after. In some winter feeding sessions, birds ate Lilly Pilly or Ligustrum fruit followed by seeds of Norfolk Island Hibiscus Lagunaria patersonii or Silky Oak Grevillea robusta, and then flew to a water-dish and regurgitated pellets while drinking. In summer, small flocks (10-15 birds) ate Ochna Ochna serrulata fruit. On 1 December 1993, an adult ate 24 Ochna berries in a short feeding bout. In December 1996, a parent and recently fledged juvenile fed together in an Ochna shrub for 6 minutes; the parent ate 31 ripe berries while the juvenile ate seven. Many Ochna seeds were voided into the water-dish in summer. Currawongs occasionally sipped nectar from Grevillea (Wood 1998, Table 5).

Hunting free-flying birds Hunting attacks on free-flying birds appeared to be opportunistic and were difficult to observe. Only one victim was seen captured: a juvenile Spotted PardalotePardalotus punctatus that fledged c. 45 seconds before the attack (Wood 1994). A second successful attack was overlooked when the Coniston breeding male was perched quietly in a dense Melaleuca and I momentarily looked away. Some 25-30 seconds later, he flew from the shrub with a juvenile House Sparrow Passer domesticus in his bill. I had not seen the Sparrow in the shrub nor had the Currawong given the impression of hunting. The Sparrow's age was confirmed when it was examined later. Prey attacks were sometimes difficult to differentiate from territorial defence, but, as well as I could judge, I witnessed another 11 attacks on free-flying birds, all of which were unsuccessful (Table 1). None of these attacks was close to the nest where defence is most intense ( <25 m), and none involved the bill-snapping or territorial calling that typifies defence. Only one unsuccessful attack was by a known female Currawong, compared with six by known males. About half of the attacks involved aerial pursuit and the others involved simple displacement of the victim from its perch or the ground. Pursuit distances ranged from 5 to 50 m. Only two attacks were on known juveniles, although the age of most victims could not be determined. The element of surprise was predominantly employed, sometimes after a restful sojourn during which the Currawong seemed disinterested in pursuing its vic:tim. The approach was Table 1 I~ Unsuccessful hunting attacks by Pied Currawongs on birds capable of flight at Wollongong, N.S.W., 1992-1996. Date Pied Cu"awong Victim Sex" Nest" Distance Approach Aerial Species (age )d Activity when attacked· from nest" flight distance pursuit distance (m) (m) (m)

15 Mar. 92 u u 25 45 Black-faced - Perched in outef foliage of Coracina novaehollandiae (J) eucalypt 5 Nov. 93 F c 25 30 0 Spotted Turtle-Dove Resting in tree Streptopelia chinensis (U) 6 Nov. 93 u :MG 40 40 0 Red-whiskered Bulbul Feeding in a small flock in Pycnonotus jocosus (U) tree 21Nov.93 M c 60 35 0 Common Myna Foraging in short grass ~ Acridotheres tristis (U) 0 0 22Nov. 93 M c 25 20 0 Common Myna (U) Perched in tree t:l 4 Dec. 93 M c 35 25 0 Red-whiskered Bulbul (U) Perched in Willow Salix 20 Sept. 94 u u 0.5 0 Rainbow Lorikeet Feeding in outer branches Trichoglossus haematodus (U) of eucalypt 12 Jan. 96 u u 10 10 Grey Perched in tree torquatus ( J) 25 Sept. 96 M MSf 45 7 50 Perched in a small flock in Stumus vulgaris (U) eucalypt ...... t:1:I 13 Oct. 96 M MSf 25 20 40 Common Myna (U) Foraging in short grass §~ 13 Oct. 96 M MSf 45 10 5 Common Myna (U) Perched in eucalypt •M=male, F=female, U =unknown. hMG= Mangerton, C=Coniston, MST= Mt St Thomas. ~~ cu=unknown dJ=juvenile, U=unknown. ~~ VOL. 18 (7) Feeding Habits of SEP'IEMBER 2000 Pied Currawong, N.S.W. 263 invariably from behind, sometimes with a shallow gliding dive. Bodies of six House Sparrows were found on the ground near the Coniston nest, and all had been opened dorsally at the pelvic girdle. The Currawongs always attempted to use their bills to capture prey. Two failed attempts resulted in removal of body feathers from the prey species.

Predation on and nestlings Although I saw no eggs taken from nests, there is one direct observation by a co-worker of a Pied Currawong stealing and eating an from a nest of the Spotted Turtle-Dove Streptope/ia chinensis (see Wood & Wilson 1997). I saw one of three nine-day-old Red-whiskered Bulbul Pycnonotus jocosus nestlings taken in 1987 (Wood 1988); one of this Bulbul's siblings fledged successfully, the other was found dead in the nest. Observations also suggest that several nestlings are sometimes taken as prey from the same nest. At the Mangerton nest, three Zosterops lateralis nestlings were fed to the young Currawongs between 0821 h and 0838 h on 30 October 1993. During a watch from daylight to dark at the Coniston nest, three nestlings of similar size and appearance were fed to the young Currawongs at 0905 h, 1523 hand 1811 h. The male carried all three prey nestlings to the nest along a particular flight path that was rarely used.

Use of feet On eight occasions Pied Currawongs were observed using their feet to handle food, two of which involved fruit. On 18 June 1995, a Currawong pulled a ripe Moreton Bay fig from the stem and carried the fig in its bill to a dead tree about 10 m away. A few pieces were pulled from the fruit while the fig was held against a branch by the bird's foot. On 16 December 1994, juveniles and adults of a family group were feeding on fruit scraps on a bird-table at the author's residence. One juvenile occasionally used its foot to hold capsicum and apple while pecking at the fruit. Six instances of handling food with the foot were at nests. At the Mangerton nest, a parent once removed a small piece of avian flesh from a larger piece that was held against the branch by the foot. At the Coniston nest, the female once used her foot to hold a large insect (30 mm in length) on the ground while pulling it apart with her bill. At Mt St Thomas, the male once stood on a fresh bone on the ground and removed a few pieces of meat by tugging in a twisting motion with the bill. The female did likewise once at the Mt St Thomas nest. During the same feeding bout, the male also took a piece of meat ( c. 60 x 10 mm) to a low branch and held it against the branch with his foot while pulling it into smaller pieces. Lastly, on 7 December 1994 at Mangerton, a Currawong captured and devoured a Greengrocer Cicada Cyclochila australasiae: the abdomen and thorax were consumed first, with the insect held against a tree branch by the bird's foot; the remaining exoskeleton was then softened by squeezing it back and forth in the bill before swallowing. These few records suggest that Pied Currawongs rarely hold food with the feet. At the five nests included in this report and six other nests, I have seen 38 birds dismembered in some 220 tearing operations. In only two of those operations was the avian prey tom apart while being held by the Currawong's foot rather than while snagged on a plant structure. Indeed, it seems that Currawongs prefer to carry avian prey in the bill to selected dismembering stations where they pull it to pieces with the bill after snagging it in plants (see Wood 1998). I have not seen a Currawong flying with food held in its feet. AUS1RALIAN 264 WOOD BIRD WATCHER

Surplus food Excess avian prey was seen abandoned by breeding birds in 14 instances. In another six instances (in the nestling period), the prey was later retrieved for consumption, within 24 hours of capture, from exposed locations at which the Currawong had last fed on it. In three instances, the prey was retrieved from a dismembering stati9n (see Wood 1998, Figure 1).

Thieving captured prey Once a Pied Currnwong was seen to steal captured prey. The Mangerton parents had almost finished dismembering a free-flying that had been fed progressively to the nestlings during the previous seven minutes. Only the head remained wedged in a crevice on a dead bough, and both parents were at the nest 15 m away, when another Currawong suddenly flew to the bough, picked up the head and flew away with it. Neither parent responded. The raid was so brief that it suggested that the intruder had been watching the dismembering process.

Pulverising food Except for small prey ( < 10 mm long), parent birds mashed food by bashing it against hard objects or by running it back and forth in the bill before eating it themselves or feeding it to young. On two occasions, snails were carried to rocks and the shells broken by bashing them against the rock. When the flesh was removed, it was pulverised and ripped into smaller pieces before it was eaten.

Discussion Observations during this study confirm that the Pied Currawong is a ground­ and foliage-gleaner (sensu Frith 1969, Ford 1985). In common with findings in (Buchanan 1989), few insects were consumed in June and July, when the diet consisted almost entirely of fruit, in Wollongong. The observations reported also suggest that the species may search for some insects acoustically (contra Brown & Veltman 1987). Such a suggestion seems plausible, since the closely related Gymnorhina tibicen locates scarab beetle larvae in the soil by listening for noise made by the grubs (Floyd & Woodland 1981 ). Moreover, some Panesthia cockroaches, in the same as that dug from the substrate at Wollongong, produce a hissing noise when disturbed (Day 1950). Pied Currawongs hold!ng the head sideways while foraging, presumably to listen for grou..'ld-dwelling prey, have been reported previously (Roberts 1942). Stripping of bark in search of insects (Roberts 1942, Crowe 1978), foraging for insects or larvae in short grass (Frith 1969, Buckingham 1994), and hawking of insects (Stokes 1982) have also been observed. Pied Currawongs at Wollongong foraged for fruit similarly to those at Wellington Point, Qld (Robertson 1969), and Armidale, N.S.W. (Bass 1990). At all these locations, large flocks (70-200 birds) gathered at fruiting trees to eat fruit in winter and regurgitated pellets soon after. Only at Wollongong, however, did some birds delay regurgitation until they ate seeds after fruit. It seems likely that dry seeds (or husks) from trees such as Norfolk Island Hibiscus and Silky Oak may assist in the formation of oohei:'erit pellets (see Buchanan 1989). Brown (1982) thought that seeds from the Flame Tree Brachychiton acerifolium served this purpose, and Rose (1973) and Hooper (1994) suggested that grass or oats VOL.18 (7) Feeding Habits of SEPTEMBER 2000 Pied Currawong, N.S.W. 265

tended to keep pellets intact. As at other locations (see Robertson 1969, Brandwood 1982, Brown 1982, Rich 1982), Currawongs at Wollongong sometimes drank water before or after regurgitating pellets. Drinking, however, did not occur immediately before or after regurgitation of most of the pellets collected at Armidale (Bass 1990, 1995 and in Litt.). Accordingly, it is suggested that Currawongs drink water to quench thirst rather than to assist with regurgitation of pellets. Other behavioural characteristics observed in the present study have also been reported previously. Roberts (1942) and Warner (1993) have seen snail­ shells broken to extract the flesh. Thieving of food, insects and prey captured by other species, has been reported by Barrett (1926), Storr (1953), Cooper & Cooper (1981), Veerman (1986), E.C. Metcalf (1988) and Portbury (1992). Use of the foot to hold food while eating in a stationary position has been mentioned by Roberts (1942), Crowe (1978), Vellenga (1980), Brown & Veltman (1987), Ross (1988), R.A. Metcalf (1988), Miller & Naisbit (1994) and Rose (1999). Data from the Wollongong study, however, suggest that Currawongs hold down food with their feet in a minority of instances. I have located only two reports (Debus in Cooper & Cooper 1981, R.A. Metcalf 1988) and one illustration (Hill 1967) of a Pied Currawong carrying captured prey in its feet while in flight. At Eden, New South Wales, J.A. Boyd (cited in North 1901) observed a Pied Currawong flying with an egg of the domestic Red Junglefowl Gallus gallus in its claws. Caching by the Pied Currawong has been reported by others (see Prawiradilaga 1994 and references therein), but was not observed in the present study. Previous descriptions are brief and the only reported instance that is consistent with the precise literal definition is that of Currawongs withdrawing pieces of food from below the surface of friable soil near Armidale (Bell 1983). As Bell (1983) pointed out, however, humans left a considerable amount of food scraps in the area, and although a Currawong could have hidden the food under the surface, humans may also have inadvertently buried it. Retrieval of surplus food from where it was last fed upon, as observed in the present study, could hardly be considered caching, as the food was neither carried to a storage site nor was it hidden for exclusive use.

Acknowledgements I am grateful to D. Priddel and three referees for constructive comments, K.R. Pullen (CSIRO) for identifying the cockroach, and Julia Hurley for diligent editing.

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