National recovery plan for the Christmas Island Goshawk Accipiter fasciatus natalis
Prepared by Richard Hill
Birds Australia
Department of the Environment and Heritage, 2004
ISBN 0 642 55009 3
Background information
Conservation status
The Christmas Island Goshawk (Accipiter fasciatus natalis) is currently listed as Endangered (EPBC Act), however, according to Garnett & Crowley (2000) it now fulfils the criteria for Critically Endangered.
Taxonomic Status
Since the Christmas Island Goshawk was described by Lister in 1888 as a full species Accipiter natalis, debate has continued over whether it is more closely allied to the Brown Goshawk Accipiter fasciatus, or to the Grey Goshawk A. novaehollandiae. Lister (1888) thought the Christmas Island Goshawk was allied to the Grey Goshawk from the Maluku A. n. griseogularis. Chasen (1933) disagreed, thinking it a member of the A. fasciatus group. The Christmas Island Goshawk may have been isolated from populations of either of these species for a long period of time, and Carter (1994) raised the possibility of resurrecting the Christmas Island subspecies natalis to a full species.
International Obligations
The Christmas Island Goshawk is not listed under international agreements.
Distribution and location
The Christmas Island Goshawk is restricted to Christmas Island, a volcanic island in the Indian Ocean (10°0'S; 105°40' E), approximately 1400 km northwest of Australia. The island sits on the northernmost edge of the Australasian continental plate, and immediately north the ocean floor drops into the Java Trench and depths of up to 6000m. The nearest land is Java in the Republic of Indonesia, 360 km to the north. Christmas Island is truly oceanic and all its native biota has colonised by sea or by air (Gray 1981). The island is 135 km2 and 75% is covered with original vegetation (Environment Australia 2002).
Gibson-Hill (1947) reported that Christmas Island Goshawks seemed to prefer areas of 'slightly thinner growth on the edge of thick jungle or the borders of clearings'. During 1994 and 1995 goshawks were observed in all major habitats on the island (Hill unpubl. data,). Goshawks were regularly seen hunting in regrowth vegetation along roadsides. This may be merely because they were much more visible in this habitat compared to intact forests. Parks Australia North (PAN) data from a systematic survey over all habitat of the island (over 1000 survey points) suggest that more goshawks are located within rainforest (95% of sightings) than in cleared areas. The Christmas Island Goshawk is the least frequently encountered diurnal forest bird and might best be described as 'widespread and uncommon'.
There are no data on adult or juvenile movements. Adult Christmas Island Goshawks are probably resident on their territories year-round. Grey Goshawks defend a territory around the nest site which appears to be significantly smaller than the home range in which they feed (Burton 1991).
There are no detailed population estimates for Christmas Island Goshawks. New Caledonian Brown Goshawks, a similar-sized closely related bird, occurred at a density of 0.89 - 0.96 adults/km2 in rainforest (Thiollay 1993). There is approximately 101 km2 of primary forest on Christmas Island which suggests that it is unlikely that there are many more than 50 pairs or 100 mature Christmas Island Goshawks on Christmas Island.
Biology
The Christmas Island Goshawk has been recorded eating a wide range of vertebrates and invertebrates including birds, small mammals and insects. Prey includes Christmas Island White-eye Zosterops natalis, Island Thrush Turdus poliocephalus, Emerald Dove Chalcophaps indica, Java Sparrow Lonchura oryzivora, domestic chickens Gallus gallus, (Lister 1888, Gibson-Hill 1947, Hill, unpubl. data); as well as nestling Red-footed Boobies Sula sula (Hill, unpubl. data) and an adult Golden Bosun Phaethon rubricauda westralis (J. Tranter pers. comm.). It has also been recorded catching rats Rattus rattus (Gibson-Hill 1947) and 'lizards' (Lister 1888). It is frequently seen catching grasshoppers (probably Valanga sp.) which are common in secondary vegetation around the island (Gibson-Hill 1947, Hill unpubl. data). Gibson-Hill (1947) also recorded it feeding on the large centipede Scolopendra morsitans, which is widespread on the island, and on beetles (Coleoptera) and mantids (Mantidae).
The Christmas Island Goshawk captures its prey off the ground or in the air by seizing it in flight with its long, strong legs. Like other goshawks, it will hunt from a perch where it may sit for some time waiting for suitable prey. Christmas Island Goshawks will chase small flying birds through the forest as well as pounce on birds foraging on the ground (Hill unpubl. data). Hill observed goshawks 'short-stay perch-hunting' (after Newton 1986) flying along a track, perching for a few minutes then flying 50-100m further and landing again, as well as pursuing insects on the ground and snatching insects off foliage. There is likely to be some sex differences in hunting and in diet, as is found in both Brown and Grey Goshawks (Marchant & Higgins 1993). Given the large sexual dimorphism (similar to Grey Goshawk, Hill unpubl. data) and the opportunity for niche expansion on the island in the absence of other diurnal raptors, this difference may be quite pronounced.
Gibson-Hill (1947) described three Christmas Island Goshawk nests all of which were in near horizontal forks of forest trees, one 10m high and two 15-20m in tall forest trees. Hill (unpubl. data) observed four nests: two in Syzygium nervosum in Primary rainforest; and two in Terminalia catappa in Marginal rainforest. All nests were 25-35m above the ground, in the fork of two or more branches, three towards the edge of the crown, and one in the middle of the tree. One nest (probably not used) was 30-40cm in diameter, two others were 50-80cm in diameter, and the fourth was under construction. Nest size and location within the tree share more similarities with Grey than Brown Goshawks (J. Young pers. comm.; see Burton et al. 1994).
Habitat
Approximately 75% of Christmas Island is still covered with natural vegetation and 84% of this (or 63% of the island) is protected within National Park (Figure 1). The remaining Primary rainforest is currently protected from clearance by a Federal Government moratorium, in conjunction with the requirements for approval under the EPBC Act and Environment Protection and Biodiversity Conservation Regulations 2000 (EPBC Regulations). Marginal rainforest and Second-growth rainforest or Secondary Vegetation outside the National Park may only be cleared if approval is given under the EPBC Act and Regulations.
Schedule 12 of the EPBC Regulations use Du Puy's classification to describe the Christmas Island forests. Primary Rainforest is restricted to the central plateau and is evergreen closed forest 30-40m high with emergent trees up to 45m. Common canopy trees include Syzygium nervosum, Planchonella nitida, and Hernandia ovigera. The canopy formed by these trees is irregular, especially on the western side of the island where it is sheltered from strong southeast trade winds which blow throughout the dry season. The understorey comprises dense thickets of Pandanus elatus up to 4m tall, and more open areas which commonly include the plants Arenga listeri, Leea angulata, Ochrosia ackeringae, Pisonia umbellifera and Aidia aff. racemosa (Environment Australia 1994).
Marginal Rainforests grow on generally shallower soils on the coastal terraces and scree slopes surrounding the island. Many Marginal Rainforest trees lose their leaves in the dry season. Marginal rainforest is generally lower than Primary Rainforest, often less than 30m, and may include many vines. The canopy height and shape are variable, determined primarily by the degree of exposure to the southeast trade winds. Marginal rainforest facing south and east has a smooth, wind-pruned canopy and tends to increase in height with increasing distance from the sea cliff. The inland cliffs and scree slopes may have no vegetation or carry a closed forest, depending on the degree of the slope. Trees such as Ficus microcarpa and Dendrocnide sinuata are common there.
Old stockpiles and cleared areas that have not been mined may support low second-growth forest of colonising trees such as Macaranga tanarius and Claoxylon indicum and an introduced tree Leucaena leucocephala generally less than 10m high. Previously mined areas tend to have very little remaining soil and on them grow dense herblands of a fern Nephrolepis multiflora to 2m high along with introduced scramblers and occasional low trees.
Habitat Critical to Survival
Identification of habitat critical to survival of the Christmas Island Goshawk is difficult due to the lack of information on specific habitat requirements. Although Christmas Island Goshawks may be generalists which forage in most habitats, it is highly likely that they require rainforest to breed as these habitat contain suitable trees. Applying the precautionary principle and using the criteria provided by the EPBC Act, habitat critical to survival of the Christmas Island Goshawks is defined as all Primary Rainforest, Marginal Rainforest (Du Puy 1993) and possibly second growth forest suitable for nesting. Primary Rainforest and Marginal Rainforest has been identified and mapped (Figure 1). Dexter (2000) recommended mapping the ecological quality of second-growth forests outside the national park. As this has not occurred, and there is insufficient information on the habitat requirements of the Christmas Island Goshawks, suitable second-growth forest cannot be identified at this time.
Affected Interests
Commonwealth Parks Australia North (PAN), Shire of Christmas Island, Christmas Island Phosphates, Union of Christmas Island Workers, the Asia Pacific Space Centre Pty. Ltd., Department of Transport and Regional Services (DOTARS), and the Department of Immigration, Multicultural and Indigenous Affairs.
Role and interests of indigenous people
Not applicable. Christmas Island does not have an indigenous population.
Social and economic impacts
The actions in this plan may have positive and negative social and economic impacts. Positive social impacts will arise from community education actions that will increase Christmas Islanders knowledge and interest in their own environment. The rainforest rehabilitation program provides on-island jobs, as will the goshawk monitoring program. Christmas Island endemic birds attract specialist bird watching groups each year which is high value, low-impact tourism.
Negative social and economic impacts arising from implementation of the plan could include greater restrictions due to review of the quarantine barrier, and potential economic effects of preventing illegal destruction of Christmas Island goshawks by residents. The EPBC Act already provides a regulatory framework for the protection of rainforest on Christmas Island, and one element of this is assessing potential impacts of proposed developments on listed threatened species. These provisions have the potential to impact on economic activity, for example by adding additional obligations for industry and other development on the island in order to minimise impacts on listed species. This arises from the listing of the species under the EPBC Act invoking a range of protective provisions and offences where a population is to be affected. The magnitude of this potential impact is unknown, as it will vary with the location, size and extent of the activity, proposed or current. However, the plan will aid in determining what could be significant impacts on the Christmas Island Goshawk (through defining habitat critical to survival and developing a management plan outside the national park).
Biodiversity Benefits:
Protection of the habitat of the Christmas Island goshawk provides protection for numerous other listed species (Table 1). Community education targeted at this species will promote awareness of all the endemic forest birds and their conservation needs.
| Taxon | National Status |
|---|---|
| Tectaria devexa var. minor | E |
| Carmona retusa | V |
| Christmas Island Pipistrelle (e) Pipistrellus murrayi | E |
| Christmas Island Shrew 1 (e) Crocidura attenuata trichura | E |
| Christmas Island Blind Snake (e) Ramphotyphlops exocoeti | V |
| Christmas Island Gecko Lepidodactylus listeri | V |
| Christmas Island Hawk-owl (e) Ninox natalis | VJ |
| Abbott's Booby (e) Papasula abbotti | E M S J |
| Red-footed Booby Sula sula rubripes | M S C J |
| Christmas Island Frigatebird (e) Fregata andrewsi | V M S C J |
| Great Frigatebird Fregata minor minor | M S C J |
|
Notes: |
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Relationship to other plans
The Christmas Island National Park Plan of Management is the strategic nature conservation document for the island. This recovery plan makes numerous recommendations in common with other recovery plans for Christmas Island threatened taxa. Opportunities for sharing resources and points shared in common with other recovery plans are identified in the implementation section of this plan.
Recovery Team
A Recovery Team for the Christmas Island Goshawk has not yet been formed. The team should comprise representatives of PAN, the Shire of Christmas Island, the Department of Transport and Regional Services, an independent environmental consultant, and other members as thought appropriate.
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