Little Tern (western Pacific) (Sterna albifrons sinensis)

Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)

1. Scientific name, common name (where appropriate), major taxon group
2. National Context
3. How judged by TSSC in relation to the EPBC Act criteria
4. Conclusion
5. Recommendation
Publications used to assess the nomination

1. Scientific name, common name (where appropriate), major taxon group

Sterna albifrons sinensis (Little Tern (western Pacific))

2. National Context

The Little Tern (western Pacific) is one of three subspecies of Sterna albifrons (Little Tern). Little Tern (western Pacific) breeds in south-eastern and eastern Asia, from India and Japan, through the Phillipines and Indonesia to New Guinea and northern and eastern Australia. Ranges of sedentary and migratory populations within Little Tern (western Pacific) often overlap.

The subspecies Sterna albifrons sinensis (Little Tern (western Pacific)) is the only form of the species Sterna albifrons (Little Tern) that occurs in Australia.

There appear to be three populations of Little Tern (western Pacific) that occur along the coast of Australia:

A population that visits Australia in its non-breeding season.
A northern Australian population that nests in northern Australia.
A south-eastern Australian population that nests in eastern Australia.

The population visiting Australia are spring-summer migrants from Asia, where they breed in the Australian autumn and winter. They sometimes occupy the same areas as the Australian breeding populations at the same times of year, but it is likely they are sexually isolated. This population is characterised by relatively large numbers that appear to be stable.
The northern population has been found breeding in northern Australia from Broome in WA, through to the Gulf of Carpentaria and east coast of Cape York Peninsula throughout the year. Little is known about these birds, and it is not known if the birds are resident or migratory. Recent and ongoing studies by the Wildlife Commission of the Northern Territory are finding the Little Tern (western Pacific) in relatively high numbers with many new breeding colonies. The breeding population in northern Australia is considered to be secure.
The south-eastern population is migratory, breeding in eastern Australia from South Australia, through Tasmania, Victoria, NSW, and into Queensland. They breed in spring-summer. This population has declined in the past, and has been the focus of conservation efforts in NSW, Victoria and Tasmania.

The two Australian breeding populations are not sufficiently distinct to warrant them being treated separately for the purposes of the EPBC Act. A number of issues were considered when making this evaluation:

Appearance: From what is currently known, there is very little difference in the appearance of birds from the three populations. However, they sometimes can be distinguished by their plumages at certain times of the year, e.g. in south-eastern Australia in spring, birds in adult breeding plumage belong to the local south-eastern breeding population, but birds in non-breeding plumage may belong to any of the three populations. Birds are only likely to be recognised as belonging to a population when they are in breeding plumage at their breeding grounds. Otherwise, it is not clear what population birds belong to.
Overlapping ranges: The migratory patterns of these highly mobile populations are complex and are poorly known. In Australia, there appears to be much overlap of populations with two or three representatives of each of the populations occurring in one area at the same time.
Information on the northern Australian breeding population: The northern breeding population is very poorly known, but recent information is showing that it is much more widespread and common than had previously been thought. Some sources have said that it breeds at different times of year than the south-eastern population, but recent information is showing a more complex breeding pattern for the northern population. It has been noted breeding nearly all year, but tending to two main periods: one between late April and July; another between September and early January.
Taxonomic/genetic differences: The taxonomic relationship between the three populations is not known. There has been some past speculation that the Australian breeding populations are actually a separate subspecies from the birds breeding in Asia, but this has not been demonstrated or widely accepted.
Two reports in the 1990s on whether genetic differences exist amongst the populations that occur in Australia are inconclusive.
Boundary between Australian breeding populations: The demarcation between the two Australian breeding populations along the Queensland coast is not clear. One source states the south-eastern breeding population extends north to round the Elliott River, northern Qld (20°S), implying the separation between breeding populations occurs round this zone. Another source claims the separation is likely to occur where there is a gap in the breeding distribution of the subspecies between Bundaberg (about 25°S) and Mackay (about 21°S). One publication states that, at the boundary where they meet, there may be an area of overlap between the two Australian breeding populations.
Ecological differences: There is a claim that the ecological differences between the two Australian breeding populations are so great that they should be considered distinct. Presumably, this is referring particularly to differences in breeding season. However, the ecology of birds in northern Australia, particularly the pattern of breeding season, seems to be poorly understood. One opinion offered suggested that avian species with Australian-wide distributions often have different breeding seasons in the north compared to the south due to local environmental factors.

In summary, there is no evidence that the Australian breeding populations are genetically distinct, the boundaries between the populations at the breeding grounds are not clear, and their movements and non-breeding areas are not known.

Taking these factors into account, there is adequate evidence to support the notion of at least two separate populations of the Little Tern (western Pacific) in Australia: a non-breeding population from Asia and an Australian breeding population. There is currently insufficient evidence to warrant dividing the Australian breeding population into two populations and thus treating the south-eastern Australian breeding population separately for the purposes of the EPBC Act.

The species, Sterna albifrons (Little Tern), is listed under the Marine and Migratory provisions of the EPBC Act. This species was previously listed as endangered under the Endangered Species Protection Act but was delisted in 1999. Under state legislation, it is listed as endangered in Queensland and New South Wales, as threatened in Victoria and as vulnerable in South Australia.

Sterna albifrons sinensis (Little Tern (western Pacific)) has recently been considered in the Bird Action Plan to be of least concern. However, the Action Plan noted there was debate on whether it should be considered conservation dependent. This subspecies is listed as endangered under Tasmanian state legislation.

3. How judged by TSSC in relation to the EPBC Act criteria

Because the Little Tern (western Pacific) does not meet both criteria, as is legislatively required for listing as conservation dependent, the TSSC judges the species not to be eligible for listing as conservation dependent under the EPBC Act. The justification against the criteria is as follows:

Criterion 1 - The species is the focus of specific conservation programs

There are no national programs in place. Breeding colonies in northern Australia are often in remote areas and these colonies are considered not under threat and stable.

In the 1970s and 1980s, it was recognised that breeding colonies of the Little Tern (western Pacific) in south-eastern Australia had fallen markedly. Currently, there are state conservation programs directed at breeding colonies in south-eastern Queensland, NSW, Victoria and Tasmania. The programs include: recovery teams, placing wardens at breeding colonies, fencing breeding colonies, relocating nests from low-lying areas and other forms of protection for breeding colonies.

Therefore, the species is eligible for listing as conservation dependent under this criterion.

Criterion 2 - The cessation of the conservation programs would on the balance of probabilities result in the species becoming vulnerable, endangered or critically endangered within a period of five years.

In Australia, the Little Tern (western Pacific) breeds on the coast from north-western Australia, through Northern Territory, to northern Queensland, and down the east coast to Victoria and Tasmania. Recently, breeding colonies have been found in South Australia. There are claims that the Little Tern is expanding its range. In 2000, the Bird Action Plan estimated the Australian breeding population as 3,000 mature individuals, though it rated the figure as having low reliability, presumably because recent surveys in more remote areas are finding it more common and widely spread in northern Australia than previously thought. In the Northern Territory, a recent survey found 44, and probably more, breeding colonies, one containing round 100 eggs and 50 young. New breeding colonies are also being found in central and northern Queensland coast and north-west Australia.

In south-eastern Australia, there appears to be around 1,000 breeding birds. The following are estimates of breeding birds in 1998: NSW, 327 (which has recently increased to c. 400 in 2001); Victoria, 400; Queensland 62; Tasmania 20 (first recorded breeding in 1968); and South Australia, 4-6 (first recorded breeding in 1972). It is probable the cessation of conservation programs in south-eastern Australia may result in the return of the regional declines in the number of breeding birds that were observed before the programs were put in place. At that time, the main evidence for decline was the following: in NSW, the estimated breeding population was c. 350 breeding pairs in 52 colonies in 1950 down to 32 pairs in 10 active colonies by 1979. In Victoria, round the 1980s, there were no declines in breeding numbers documented, but fledging success was found to be very low. In Tasmania, where it was first recorded breeding in 1968, there were up to 11 breeding sites in the 1970s and 1980s, with one colony having 82 breeding birds. Now it has an estimated 20 breeding birds in total, with conservation programs put in place in the last few years. The main causes of decline in south-eastern Australia were: loss of breeding sites to development; predation by foxes and cats; human disturbance that destroys eggs and young or leaves them vulnerable to Silver Gulls and ravens/crows; loss of colonies by high tides; and loss of sites through natural vegetation succession.

It is probable that if the conservation programs that are directed at the approximately 1000 breeding birds in south-eastern Australia ceased, the number of breeding birds in this region may decline. However, the impact of the decline on the total Australian breeding population is not likely to be significant as the large number of birds that breed across northern Australia is stable and secure. If the conservation programs ceased, the Little Tern (western Pacific) is not likely to become vulnerable, endangered or critically endangered at a national level within a period of five years.

Therefore, the species is not eligible for listing under this criterion.

4. Conclusion

Currently, it is estimated that there are 3,000 breeding birds in the Australian breeding population of the Little Tern (western Pacific). An estimated 1,000 of these nest in south-eastern Australia. As a result of past or predicted declines in adult numbers in the south-eastern region, many of the breeding colonies in south-eastern Australia have been the focus of conservation programs over the last 20 years or so. If these programs were removed, it is probable that the number of breeding birds in the south-eastern region would again decline, but the larger number of breeding birds in northern Australia would remain stable and secure. From a national perspective, the Little Tern (western Pacific) is not eligible for listing under the EPBC Act.

The species is not eligible for listing as conservation dependent.

5. Recommendation

TSSC recommends that the species Sterna albifrons sinensis (Little Tern (western Pacific)) is not eligible for inclusion in the conservation dependent category of the list referred to in section 178 of the EPBC Act.

Publications used to assess the nomination

Reference list and any other relevant information used to assess the nomination.

Chatto, R. 2001. The Distribution and Status of Colonial Breeding Seabirds in the Northern Territory. Technical Report 70-2001. Parks & Wildlife Commission, NT.

Dept. Natural Resources & Environment. 2000. Action Statement 51 - Little Tern Sterna albifrons sinensis. DNRE, Victoria.

Donnellan, S. 1995. Final Report on the Consultancy Service: Taxonomy of the Little Tern (Sterna albifrons) SCAP Project No. 4111. Unpublished report to the Australian Nature Conservation Agency.

Donnellan, S. 1996. Report on the Consultancy Service: Genetic Analysis of the Little Tern (Sterna albifrons) Phase III. Unpublished report to the Australian Nature Conservation Agency.

Garnett, S.T. & G.M. Crowley. 2000. The Action Plan for Australian Birds. Environment Australia, Canberra.

Higgins, P.J. & S.J.J.F. Davies. 1996. The Handbook of Australian, New Zealand and Antarctic Birds. OUP, Melbourne.

Lane, B.A., M.R. Benzuijen & V. Wong. 1998. 1998 Little Tern Recovery Plan - Draft. Ecology Australia & Environment Australia.

NSW NPWS. 2000. Little Tern (Sterna albifrons) Recovery Plan - Draft for Public Comment. NSW NPWS.