Abstract
INTRODUCTION
The Lord Howe Island woodhen Tncboiimnas sylvestris is an endangered flightless rail (family rallidae) endemic to the tiny southwest Pacific Island of the same name. This paper reports on an avicultural programme which recently commenced on the Island to provide captive-bred srock for rehabilitation of the species in the wild.
Lord Howe Island lies approximately 800km northeast of Sydney, New Sou th Wales, Ausualia. The nearest land is the coastline of the Australian mainland, some 600km away. The island is small (9km long by 2km wide) and mountainous, and for the most part covered in sub-tropical rainforest. Mounts Lidgbird and Gower dominate the landscape, and the 20 hectare plateau summit of the latter (altitude 866m) was the woodheri's last stronghold. The lowlands of the island are inhabited by some 250 people, many of whom are the direct descendenrs of the first settlers of 1833.
Previous ecological studies of the woodhen had shown the woodhen to be one of the world's rarest birds, with a total population in the wild of some 30 individuals (Disney 1974, Fullagar and Disney 1975, Miller and Kingston 1980). During May 1980 only fifteen individuals could be found. It has been ranked by the IUCN as an endangered species on its highest priority list (endangered genera and higher taxa). In mid-1980, an aviculrural programme was embarked upon to assist with the conservation of the species on the island. I was appointed aviculrurisr and after the first season wish to report on progress to date, with details of methods employed and aspects of the bird's breeding biology not previously reported.
DESCRIPTION AND HABITS
The woodheri's general colour is olivebrown, and wing feathers are chestnut coloured with black bars although this is not seen until the birds spread their wings. The bill is approximately 50mm long, slightly down curved and pinkishgrey in colour. The oldest birds sometimes have white ear coverts and occasionally, a grey nape. The iris in adults is bright red. The bantam-sized woodhen of Lord Howe Island are very alert and move quickly when disturbed but they can be attracted within a few feet by an unusual noise. Both members of a woodhen pair are extremely aggressive
when defending their territory assaulting the intruder merciless! y.
The woodhen' s territorial call is highpitched. Both birds of a territorial pair combine together in their challenging duet. Established pairs maintain a low 'bonking ' contact call. Woodhen chicks, while growing, emit an incessant 'peeping.'
Although the birds spend most of their lives digging and scratching for insects and other invertebrate foods, they have never been observed scratching with their feet as does a chicken, or holding food items with their feet as do parrots. While scratching amongst the forest litter for invertebrates, they can move objects using the bill such as logs etc., equal to their own weight.
Lord Howe Island showing current wood hen distribution and the site of the captive breeding colony and re-introduction of freeranging colonies.
Regarded as flightless, in captivity woodhen have been observed to jump vertically up to 1112 metres entirely wirh the power in their legs and to skim the ground horizoncally for 3 112 metres with their wings flapping and rheir legs dangling behind.
In 183 7, woodhen were reported to be still common, but only sixteen years later were scarce and restricted in distribution due to the efforts of the first settlers who
arrived in 18 33 and hunced birds for food.
Concinuing human predation, coupled with the impact of introduced pigs, goats, cats and owls reduced the woodhen population still further. Woodhen were still regularly on the menu seventy years ago. Accounts from the island's senior citizens describe how at the turn of the century they, as children, used to knock stones or sticks together, as the banging would attract the birds. Once the birds were close, they would hit them on the head.
Some woodhen still persisted on the lowlands uncil the 1940's, but since then, there have been few reports below the summit and upper slopes of Mount Gower.
Concrol/ eradication programmes on introduced predators and competitors have been undertaken in recent years in a bid to help the woodhen population. Pigs have been almost exterminated and the other animal populations greatly thinned. It is against this background of habitat rehabilitation that the captive propagation I release programme for the woodhen is being undertaken. INVESTIGATIONS-
PAST AND PRESENT
In 1969, Mr. H.J. de S. Disney, the then Curator of Birds at the Australian Museum began studies on the woodhen. Dr. P. Fullagar of the C.S.I.R.O. joined him in 1971 and results of their researches revealed that there were less than thirty woodhen on Mounc Gower and possibly a few on Mounc Lidgbird.
Their observations revealed that adults paired for life and, on the summit, each pair defended a territory of approximately 2 or 3 hectares. The population size remained almost constant: the number of young birds hatched and surviving each season was about equal to the number of adult deaths. Juvenile birds were forced out of the parents' territories during the wincer months. All birds were caught and banded with aluminum serial numbered bands and, for easy identification, a unique sequence of coloured bands on the other leg e.g. yellow-red-green so that data sheets would be headed with the colour band sequence, followed by derails. Many birds were banded as juveniles in their family groups, but were never seen again. It was surmised that these birds perished due to lack of suitable habitat.
In 1978, Dr. Ben Miller of the New Sourh Wales National Parks and Wildlife Service spent two years on Lord Howe Island to make a full investigation into the problems limiting the woodhen population and what might be done to
help increase what still remained. He concluded that feral pigs were preventing the woodhen population descending from its mountaintop refuge, which was protected by a low cliffline and hence inaccessible to the pigs. Only this accident of topography had saved the woodhen population from extinction. Based on these findings, a pig eradication programme was commenced in 1979, and almost 200 pigs have been removed from the forests, with only one or two thought to remain. Miller and Dr. Tim Kingston of the Australian Museum (1980) examined a number of alternative sites on the island, with the view to reestablishment of additional woodhen populations and found that the food resource was adequate in most places. At one site, Little Slope, the food resource was extremely rich, and with an absence of pigs, goats and cats, there was no reason why restocking would not result in the foundation of a substantial wild population. Many areas of the native forest started to regenerate with strategies primarily addressed to woodhen.
THE BREEDING PROGRAMME Costs and Source of Funds
Before an attempt could be made to propogate the woodhen, long-term financial backing was sought from the National Parks and Wildlife Foundation which operates as a fund-raising trust by public and business donations for many wildlife projects in New South Wales. The National Parks and Wildlife Service undertook administration responsibilities and the Lord Howe Island Board (which is responsible for the administration of the island) assisted with rent subsidies and construction of facilities, use of vehicles and manpower, etc. As many of the administrating costs of the Service and the Board are hidden, the real final cost will be somewhat higher than the estimate provided below.
Aust. $
Investigative Study (2 years) 62 ,000
5 year Breeding Programme 200,000
262,000 Site and Construction
The breeding complex was built on a specially selected reserve on the lowlands of the island in near-natural habitat of Banyan Fig (Ficus colurnnatis), Kenna Palm (Hou/ea forsterana) and Blackbutt Cryptocaria triplinervis forest.
Construction of the 0. 5 hectare breeding centre was completed in May 1980. The breeding aviaries are protected by a perimeter fence 225cm high comprising overlapping palings 200cm which supports an outward sloping tin guard of 25cm from which suspends
three strands of electric wmng to discourage animals climbing over the top from outside. To prevent animals burrowing under, a 45cm tin strip sits under the palings. This has proved an adequate protection against disturbance from cats, dogs, and humans.
The initial concept of large opentopped enclosures proved unsatisfactory as, on the first night in it's breeding enclosures, a male woodhen was killed by a Tasmanian masked barn owl (Tyto novaehollandiae). This owl species had been introduced to the island in the 1920's in an effort to help control the increasing rat population. To eliminate further loss to owls, each aviary followed a basic format having galvanized iron or netted l 50cm high sides with a flat or pitched roof, depending on location in an effort to minimize damage to trees. Solid galvanized iron sides face the other aviaries to reduce visual and some audible disturbances. The surface area of each aviary was approximately 100 square metres. The aviary adjoining the Service building (see Diagram) is fitted with a glass viewing strip which enables the public to view juvenile I nonbreeding birds with minimal disturbance to them.
The Service building is divided into two rooms: one for preparing food also serving as an office area. An air conditioner maintains constant temperature of the Incubator/brooder room which is fitted with two incubators:
-The Domex 'forced draft'; and
-The Onslow 'still air' .
Refer to Figure 2 for general layout of aviaries and building.