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AUSTRALIAN BIRD WATCHER 1988, 12, 217-221

Little Bitterns Breeding in Northern Australia

by ROGER P. JAENSCH, 30/15 Ogilvie Road , Canning Bridge, W.A. 6153

Summary The Little Bittern Ixobrychus minutus was first recorded in the north of Western Australia in January

1982 and March 1983, in extensive tall rushland of Typha at Packsaddle Swamp, near Kununurra. Three nests with eggs of the Little Bittern were found there in January 1985; this was the first record of breeding by this species in northern Australia. The occurrence of Little Bitterns near Kununurra may be a result of migration from southern Australia.

Introduction Five subspecies of the Little Bittern Ixobrychus minutus are generally recognised

(Hancock & Elliot 1978). The nominate subspecies minutus breeds from western Europe, through North Africa and central Asia to Sinkiang, Nepal and Assam, and migrates mainly to eastern and southern Africa. Birds of this subspecies in the Indian region are sedentary, or at most, local migrants. Two other subspecies, both sedentary, occur in the African region: payesii in all but northern parts of Africa and podiceps in Madagascar. The status of the New Zealand subspecies novaezelandiae is uncertain and there have been no confirmed sightings this century (Hancock & Elliot 1978).

The Australian subspecies dubius mainly occurs in south-western and south-eastern parts of the continent. Before 1982, the only records of dubius in tropical Australia were from scattered localities on the Queensland coast, from Booby Island (Torres Strait) and from Groote Eylandt (Blakers et al . 1984). This subspecies also occurs in New Guinea: a single specimen from the middle Fly River (Lake Daviumbu) is mentioned by several authors (e.g. Rand & Gilliard 1967). Reports of small numbers occurring regularly at Moitaka, near Port Moresby (e.g. 20 in February 1981: Anon. 1981), may be attributable to the subspecies dubius.

There were no confirmed breeding records of I. m. dub ius north of latitude 29 degrees south, before 1982 (Blakers et al. 1984).

First records in the north of Western Australia A female Little Bittern was observed in tall rushland of Typha sp. at Lake Kununurra,

near the Ord River Diversion Dam, on 4 January 1982, by D. Eades, C. Corben, D. Robinson, K. Bartram, G. Ingram and A. Smyth (D. Robinson & D. Eades pers. comm.). On 6 January 1982, these observers saw five Little Bitterns (both sexes recorded) at the same locality, and heard additional birds calling. These were the first records of the Little Bittern in the north of Western Australia; all previous records of this species were from the south-western part of the State, as far north as the mouth of the Murchison River (Serventy & Whittell1976; Blakers et al. 1984). The nearest known locality for the Little Bittern, Groote Eylandt, is 850 km distant from Kununurra.

On 13 March 1983, I saw an adult male Little Bittern in tall rushland of Typha sp. at East Packsaddle Swamp. This wetland is 4 .0 km south-west of Kununurra and it adjoins Lake Kununurra. It contains extensive beds of Typha, areas of open water or waterlilies, and dead trees. Water in the Packsaddle Swamps is usually maintained

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at a constant level by the Ord River Diversion Dam, and water was about 0.5 m deep at the site of the observation on 13 March 1983.

The bittern observed on 13 March 1983 was identified as a Little Bittern because its back was uniform black. This feature is characteristic of an adult male Little Bittern. The Yellow Bittern /. sinensis, Cinnamon Bittern /. cinnamomeus and Schrenck's Bittern /. eurhythmus are each of similar size to /. minutus and occur in nearby Indonesia, but none of them has a black back (Hancock & Elliot 1978).

In the early morning of 14 March 1983, I heard the distinctive, croaking call hork­hork-hork ... of a Little Bittern at the site where I saw the bittern on 13 March, and two Little Bitterns were calling there at dusk on 20 March. This call is apparently given only by the male of this species (pers. obs.; Hancock & Elliot 1978), usually at the onset and early stages of breeding. I searched for nest-: of the Little Bittern in areas of tall, partly collapsed Typha and tall erect Typha at East Packsaddle Swamp, but did not find any in March 1983.

Nevertheless, K. Mills and I saw a juvenile Little Bittern at the same locality on 15 March 1983; this suggests that Little Bitterns may have bred there in early 1983. The bird was judged to be a juvenile because its plumage was generally rich buff with blackish streaks, and it lacked any contrasting dark plumage on its head, wings or back. It was not an adult female Little Bittern, which has dark grey-brown primaries and a red-brown back, nor an adult female or immature of the Yellow Bittern, both of which have black primaries and outer secondaries (R. Jaensch unpubl. manuscript) .

Breeding near Kununurra in January 1985 At 1100 h on 1 January 1985, I saw a Little Bittern flying low above open water

and Typha at East Packsaddle Swamp. This bird lacked strong contrast in colour between its primaries and lesser upper-wing coverts and was therefore an immature or female. An adult female Little Bittern was clearly seen at 0450 h on 3 January 1985 at another (third) locality in the Lake Kununurra wetlands, i.e. tall rushland of Typha near the Kununurra Power Station.

In the hope of confirming that Little Bitterns breed in the Lake Kununurra wetlands, I observed movements of waterbirds at East Packsaddle Swamp from the top of a low tree from 0430 to 0630 h on 4 January 1985. Only one Little Bittern was seen, but I decided to look for nests in the tall Typha in which it alighted.

A nest was found at 0800 h in an area of dense Typha, about 30m long and 20 m wide, surrounded by open water. A small bittern was flushed from the nest, about three metres ahead of me, uttering a clipped call cuck-cuck-cuck-cuck. The nest was in erect Typha growing to a little over 2.0 min height, with numerous seed-bearing stalks (seed spikes as yet unopened), and was situated 4.0 m from the edge of open water. There was a small canopy of interwoven green rush about 0.3 m above the nest, near the top of the rush bed. Water beneath the nest was 0.4 m deep at the time. The nest was a shallow bowl built from fine pieces of dead Typha and was about 8 em thick. It contained three white eggs which were heavily stained.

After five minutes the bittern returned to the vicinity of its nest, giving sharp calls cuck or cuck-cuck and raising feathers on its crown, neck and chest as it moved stealthily through the rush. It was seen clearly from a distance of 1.5 m as it climbed to the top of a seed-bearing stalk and was identified as an adult female Little Bittern because it had a brown back, black cap and grey-brown primaries. The male Yellow Bittern has black primaries.

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Eggs of Little Bittern lxobrychus minutus, Yarnup Lake, W.A. Plate 49 Photo: Roger J aensch

Little Bittern nestling assumes protective pose, Jandabup Lake, W.A. Plate 50 Photo: Roger Jaensch

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About 30 minutes later, while searching a separate area of Typha about 30 m from the first nest, I heard a sharp call cra-a-a-a-k, cuck-cuck-cuck-cuck. An adult male Little Bittern was subsequently seen atop green stems of Typha that were 2.5 min height, uttering single calls cuck. It had pink colour at the base of its bill, which is probably indicative of early stages of breeding (pers. obs.). Careful searching failed to reveal an active nest at this site.

While searching at a third site, 30 m distant from the second but in the same area of rush, I heard loud calls cuck and saw an adult female Little Bittern atop a seed­bearing stalk. A nest, the second found in the Swamp, was discovered at this site; it held three un-stained eggs. It was similar to the first nest in every respect, though the supporting Typha was a little taller.

On 6 January 1985, I searched other parts of the Swamp but did not find additional nests. However, I returned to the first nest at 1600 h and flushed an adult male Little Bittern from it. At the same time, another male began to call at the far end of the same area of Typha. I investigated the far end and subsequently found a (third) nest about 20 m from the first, with two stained eggs in it. The nest was similar to the first in most respects, including a canopy, but supporting rush stems were 1.0 m taller and the nest was closer to the water. An adult Little Bittern was seen alighting near it later in the afternoon.

While checking the second nest on 6 January, I flushed an adult male Little Bittern from it; this was a different male from that seen 30m from the first nest on 4 January, because it had a different pattern of striping on its chest. This therefore confirmed my suspicion that the male of 4 January was associated with another (fourth) nest.

On 7 January 1985, the first nest still held three eggs and a male was incubating them, but the nest was tilted and empty when inspected six days later (K. Mills pers. comm.). It is possible that disturbance of the nesting bitterns by the observers over several days had alerted a predator which had later raided the nest. I have known nestlings of the Little Bittern to roam from a nest after eight days from hatching, but there was no shell in this nest to indicate that the eggs had hatched. The outcome of the second and third nests was not determined. Discussion

There is some evidence (calls, juvenile sighted) to suggest that Little Bitterns bred in the Lake Kununurra wetlands in 1982 and 1983, but breeding there by Little Bitterns was only confirmed with the discovery of three nests with eggs in 1985. This was the first record of breeding by the Little Bittern in northern Australia; the latitude of Kununurra is 15 degrees, 46 minutes south.

Swamps containing Typha and other tall, dense plants occur naturally in the Kimberley Division (pers. obs.). However, many of these wetlands are seasonal and hold water for less than six months. Completion of the Ord River Diversion Dam at Kununurra in 1963 led to permanent flooding of the Ord Valley (to form Lake Kununurra), and adjacent gently sloped land, and these areas were extensively colonised by Typha after a number of years. The Lake Kununurra wetlands now constitute one of the largest areas of permanently inundated tall rushland in northern Australia; tall green Typha occurs there throughout the year. (Typha dies and collapses in southern Australia in winter) .

The ability of Little Bitterns to colonise these wetlands may be a result of long distance migration through northern Australia by this species. Whereas Hancock & Elliott (1978) had little evidence of migration by the Australian subspecies of the Little Bittern, recent work suggests that the subspecies may be migratory. There are few

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records of Little Bitterns in southern Australia in late autumn and early winter (Parker et al. 1979; Morris et al. 1981; RAOU data summarised in Jaensch in prep.). Furthermore, Blakers et al. (1984) suggest that, on the basis of data from the RAOU Field Atlas, Little Bitterns may leave Australia in winter, and that Little Bitterns recorded at Booby Island may have been migrating.

It is possible that Australian Little Bitterns migrate from southern Australia through northern Australia to New Guinea and perhaps Indonesia each year. Some Australian birds migrate or wander to New Guinea (e.g. Intermediate Egret Egretta intermedia: Blakers et al. 1984), or Indonesia, and Little Bitterns of the nominate subspecies migrate over long distances, some crossing the Sahara Desert (Hancock & Elliot 1978). Whereas Little Bitterns are known from few localities in New Guinea and are not known in Indonesia, future surveys of vast wetlands in these regions (e.g. southern Irian Jaya) may reveal numbers of Little Bitterns.

Colonisation of the Lake Kununurra wetlands by Little Bitterns may have occurred because the bitterns discovered this new habitat while passing the area on migration. Given that these wetlands are probably suitable for bitterns throughout the year and that Little Bitterns breed there at the same time that many Little Bitterns breed in southern Australia (e.g. January), it is therefore likely that some of the Little Bitterns occurring at Kununurra are now sedentary. Some Little Bitterns appear to be sedentary at Groote Eylandt (Blakers et al. 1984) and probably also near Port Moresby (Anon. 1981). The bird recorded in the Fly River region of New Guinea in September was a female ready to lay (Rand & Gilliard 1967); this may be evidence of a sedentary population in New Guinea, assuming that birds returning to Australia from New Guinea would have departed New Guinea by September. Some populations of the nominate subspecies are sedentary and Yellow Bitterns have established sedentary populations in their wintering grounds in South-East Asia (Hancock & Elliot 1978).

Further work may clarify the status of the Little Bittern in the Lake Kununurra wetlands; thorough surveys in winter are needed. Observers at other locations in northern Australia should be aware of the possibility of Little Bitterns passing their area in autumn or winter.

Acknowledgements

I am grateful to David Eades et al. for allowing me to publish their observations. Special thanks are due to Ken and Liz Mills for their hospitality at Kununurra.

References Anon. (1981), 'February field outing to Moitaka Settling Ponds', P.N.G. Bird Soc. News/. 175-176, 2. Blakers, M., Davies, S.J.J.F. & Reilly, P.N. (1984), The Atlas of Australian Birds, Melbourne University

Press, Melbourne. Hancock, J. & Elliot, H. (1978), The Herons of the Ubrld, London Editions, London. Jaensch, R.P. (in prep.), Waterbirds in Nature Reserves of South-Western Australia, 1981-1985, West.

Aust. Dept Conserv. & Land Manage. Spec. Pub!. (RAOU Report 30). Morris, A.K. , McGill, A .R . , & Holmes, G. (1981), Handlist of Birds in New South Ubles, N.S.W.

Field Om. Club, Sydney. Parker, S.A. , Eckert, H.J., Ragless, G.B. , Cox, J.B. & Reid, N.C.H. (1979), An Annotated Checklist

of the Birds of South Australia. Pan 1: emus to spoonbills, Sth Aust. Om. Assoc., Adelaide. Rand, A .L. & Gilliard, E.T. (1967), Handbook of New Guinea Birds, Weidenfeld & Nicolson, London. Serventy, D.L. & Whittell, H.M. (1976), Birds of Western Australia, 5th Edn, University of W.A.

Press, Perth.

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