VOL. 13 (3) SEPTEMBER 1989 SMITH: Young Pallid Cuckoo 99

Thereafter although the nest was observed weekly, usually for a whole day, until the chicks became independent only Blue and Green were seen. The male seemed to have a pair bond with both females. Green showed a degree of tolerance towards Yellow not shown towards 'strange' egrets, indicating some familiarity between the two females. However, their relationship obviously fell well short of the mutual acceptance needed for co-operative rearing of the young. Lancaster (1970) suggested that trios fail because one female 'forms a stronger bond' (presumably with the male) 'forcing the departure of the other' but this does not explain the mechanism which actually forces the departure. In the present case it seems most probable that Green's antagonism to Yellow caused the latter to abandon the nest. Bigyny would enhance the breeding success of the male and of the secondary female if she had been unable to establish a monogamous relationship. The primary female would gain only if the contribution of the secondary female enhanced the survival of the first's offspring. This would be the case if the secondary female contributed, for example, one-third of the parental investment but less than one-third of the eggs. Where there is a shortage of males in a heronry or a shortage of some breeding resource, bigyny seems a useful alternative mating strategy to monogamy in these colonially nesting birds. The increasing number of studies of uniquely marked ardeids may reveal bigyny to be more common than is presently realised. We are grateful to Mr A. Jahnke for permission to visit the heronry on his property and to the Darling Downs Institute of Advanced Education for financial support. References Blaker, D. (1969), 'The behaviour of Egretta garzetta and E. intermedia', Ostrich 40, 150-155. Cramp, S. (Chief Ed.) (1977), Handbook of the Birds of Europe, the Middle East and North Africa, Vol. I, Oxford University Press, Oxford. Fujioka, M. (1986), 'Two cases of bigyny in the Cattle Egret Bubulcus ibis', Ibis 128, 419-422. Lancaster, D. A. (1970), 'Breeding behaviour of the Cattle Egret in Columbia', Living Bird 9, 167-194 . McKilligan, N. G. (1985), 'The breeding success of the Indian Cattle Egret Ardeola ibis in eastern Australia', Ibis 127, 530-536. Palmer, R.S. (Ed.) (1962), Handbook of North American Birds , Vol. I, Yale University Press, New Haven and London. By N.G. McKILLIGAN and P. McCONNELL, School of Applied Science, Darling Downs Institute of Advanced Education, Toowoomba, Queensland 4350 Received 28 December 1988 •

Feeding of Young Pallid Cuckoo by Four Passerine Species

At 1800 h on 26 November 1987 I was in a garden near Tamagulla, in central Victoria, when a pair of Hooded Robins Melanodryas cucullata flew in and began gathering food (mostly small moths). When their beaks were full, they flew uphill into the adjoining mixed eucalypt forest (mainly Yellow Gum Eucalyptus leucoxylon and Mugga Ironbark E. sideroxylon). I followed them to where I subsequently found a fledgling Hooded Robin. After having flown about 150 m, the two adult robins chased a young fully grown Pallid Cuckoo Cuculus pallidus in mottled black and white juvenile plumage, whilst emitting their scolding call used when defending the territory or nest. The cuckoo alighted on a branch about 5 m above the ground and immediately began to beg AUSTRALIAN 100 SMITH: Young Pallid Cuckoo BIRD WATCHER

vigorously. The wings were half open and raised and lowered rapidly, the head was thrust forward and the bird uttered a soft wheezing note. The two robins perched one on either side of the cuckoo which turned to face them alternately and, after some apparent hesitation, fed it with the food they had gathered. Even before they had departed, they were joined by a Yellow-tufted Honeyeater Lichenostomus melanops which immediately fed the cuckoo. Then, before the Yellow-tufted Honeyeater had left, it was joined by a White-plumed Honeyeater L. penicillatus which promptly fed the cuckoo. The robins and Yellow-tufted Honeyeaters continued to feed the cuckoo, which changed its perch several times. On several occasions two Yellow-tufted Honeyeaters were present at the same time, as were the robins. On one occasion, a female Rufous Whistler Pachycephala ru.fiventris fed the cuckoo. I observed the interaction between these birds for over an hour; the cuckoo maintained a continuous begging posture, but did not always use vocal solicitation. During this time the Yellow­ tufted Honeyeater fed the cuckoo about 20 times, and the Hooded Robins fed it about 10-12 times. They fed the cuckoo on average about once every two minutes, although on several occasions there were three birds on the perch with it - two departing after having fed the cuckoo, and one arriving. I returned at 1000 h on the following morning and quickly located the fledgling cuckoo. The cuckoo continued to beg and four birds (two Hooded Robins and two Yellow-tufted Honeyeaters) fed it regularly and frequently; during the following 1Vz hours the robins fed it about 15-18 times and the honeyeaters fed it about 20-30 times. I did not see either the White-plumed Honeyeater or the female Rufous Whistler feed the cuckoo. I did not see or hear an adult Pallid Cuckoo on either day. The time spent by the cuckoo in changing perches occupied about half of the total observation period on both days. On three or four occasions on each day, all four birds were on the same perch as the cuckoo, queued up to feed it. I found a recently fledged Hooded Robin on the second morning near the young cuckoo, which indicates that the adult robins had not reared the cuckoo. It is likely that the Yellow-tufted Honeyeaters were its foster parents, partly because they fed the cuckoo so assiduously and partly because honeyeaters of several species are the usual biological hosts of the Pallid Cuckoo. The food appeared to consist of moths, with an occasional green caterpillar. The robin chick was barely able to fly, from which I inferred that it had left the nest earlier on the morning of Z1 November. I found only one chick. I saw the parent robins feed the chick once, but had the impression that they were neglecting their own chick in favour of the cuckoo, which they fed often. The four birds - the pair of honeyeaters and the pair of robins - were still responding to the begging of the cuckoo when I departed at 1130 h. Similar incidents to the above have been described previously (e.g. Chaffer 1973, Woodell et al. 1985). The fledgling cuckoo is much larger than most of its hosts, which together with the conspicuous begging behaviour and persistent calls, may act is a 'supernormal' stimulus to encourage the attention of the foster parents and any other passing birds which may be in a receptive stage of their own breeding cycle. Thus, other birds may be diverted from feeding their own young. References Chaffer, N. (lm), 'Unusual behaviour of a young Pallid Cuckoo', Aust. Bird Hiztcher 5, 10-12. Woodell, R.J. , Woodell, J.D. & Woodell, R. (1985), 'Interactions of a juvenile Pallid Cuckoo and three other species', Emu 85, 126-127. By L.H. SMITH, 36 Duke Street, Kew, Victoria 3101 Received 9 February 1989 •