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Part B: Conservation Issues For Specific Species/Groups

• 1. Herald petrel & Round Island petrel
• 2. Soft-plumaged petrel, blue petrel & fairy prion
• 3. Heard shag & Macquarie shag
• 4. Antarctic tern (New Zealand) & Antarctic tern (Indian Ocean)
• 5. Australian lesser noddy

1. Tropical Gadfly Petrels - conservation issues

• 1.1 General Introduction
• 1.2 Taxonomy
• 1.3 Distribution
• 1.4 Population Size and Trend
• 1.5 Breeding Biology, Ecology and Diet
• 1.6 Threats specific to the Herald Petrel and Round Island Petrel
• 1.7 Issues and Recommendations
• 1.8 References
• Table 1.9: Summary of biological information for Herald Petrel and Round Island Petrel

Herald Petrel	Pterodroma heraldica
Conservation Status	Native Species
BirdLife International Status	Least Concern
EPBC Status	Critically Endangered
Round Island Petrel	Pterodroma arminjoniana
Conservation Status	Native Species
BirdLife International Status	Vulnerable
EPBC Status	Critically Endangered

1.1 General Introduction

The gadfly petrels (Procellariidae: Pterodroma spp.) are a group of highly oceanic seabirds, comprising some 30 species, that are complex in plumage and taxonomy (Nelson 1980). Found throughout the ocean basins of the world, they are widely distributed in the tropics and sub-tropics, but with some species breeding in the subantarctic zone (Warham 1990). They are adapted to a highly aerial and oceanic life, and possess short sturdy bills adapted for seizing soft prey at the surface, and unusual helicoidally twisted intestines. The function of the twisted intestines is obscure but believed to assist in digesting marine animals that have an unusual biochemistry (Imber 1985, Kuroda 1986). They also show complex markings on the face and wings that are thought to serve as interspecific recognition characters (Murphy and Pennoyer 1952).

As a group gadfly petrels vary considerably in size (160-525 g, Warham 1990). The Herald petrel (Pterodroma heraldica) and Round Island or Trindade petrel (P. arminjoniana) are medium to large-sized gadfly petrels, (280-450 g; Gardner et al. 1985), and are 34-39 cm long with a wingspan of 80-100cm (Marchant and Higgins 1990). Their plumages are well described in the literature (Marchant and Higgins 1990), and both species are polymorphic, possessing both light and dark morphs. For both species the genders and young birds are similar in appearance.

The Herald Petrel and Round Island Petrel are both tropical/sub-tropical species and are considered to be closely related (Imber 1985; Brooke et al. 1996; Brooke et al. 2000). Historically they have been considered by some authors to be conspecific e.g. Warham (1990).

1.2 Taxonomy

P.arminjoniana and P.heraldica are extremely similar in appearance and have been the subject of considerable taxonomic debate. Taxonomic resolution has been hampered by the considerable plumage variation in both species/forms - both are polymorphic with dark and white-bellied morphs, as well as intermediate forms occurring. Much of the taxonomic history for these birds has been summarised by Brooke and Rowe (1996).

P.arminjoniana was described by Giglioli and Salvidori (1869) on the basis of a type specimen (white-bellied morph) collected in 1868 near Trindade Island in the South Atlantic Ocean. In 1948 another population was discovered breeding on Round Island off Mauritius in the Indian Ocean (Vinson in Gardner et al. 1985). Murphy and Pennoyer (1952) considered the Indian Ocean specimens to be quite indistinguishable from the South Atlantic examples but definitely larger than birds from the South Pacific (see below). No scientific names have been ascribed exclusively to the Round Island Petrels which occur in dark, light and intermediate forms.

From the Pacific, Aestrelata (Pterodroma) heraldica was described in 1888 from two (white-bellied) specimens obtained at Chesterfield Island, northwest of New Caledonia. P. heraldica was subsequently found to have an extensive South Pacific breeding range, and also to occur in both light and dark forms (Warham 1990).

Despite the size differences between arminjoniana and heraldica (the former is larger) Murphy and Pennoyer (1952) treated heraldica as the Pacific representative of Atlantic arminjoniana.

In the next major review of the genus Pterodroma, Imber (1985) gave specific status to both arminjoniana and heraldica because of their geographic separation and because they host different Halipeurus feather lice. Warham (1990) subsequently restored heraldica to subspecific status, believing Imber's (1985) classification to be radical because it was based on gut morphology and parasite-host associations which were not proven as reliable taxonomic characters.

Brooke and Rowe (1996) and Brooke et al. (2000) used molecular data from the Pitcairn Islands and Round Island, together with other biological evidence, to assess the taxonomic relationships of P. arminjoniana, P. heraldica and the Kermadec Petrel P. neglecta. They believed the molecular data confirmed that heraldica and arminjoniana were closely related, but were reluctant to assert that Round Island Petrels should be assigned to heraldica rather than, as had been traditional, to arminjoniana. It should be noted that in conducting their molecular analyses, neither Brooke and Rowe (1996) or Brooke et al. (2000) had genetic samples from true P. arminjoniana from Trindade Island in the Atlantic for analysis, throwing into question if, in fact, the birds from Round Island and Trindade Island are conspecific.

More recently, BirdLife International (2004), quoting Brooke (2004) as the source of their taxonomic advice, believed that P.arminjoniana, although normally regarded as conspecific with P. heraldica, was closer to the Kermadec Petrel P. neglecta in many respects. Further, they believed that the Pterodroma population on Round Island could be assigned to either P. arminjoniana or P. heraldica.

Specimens of Herald Petrels from Raine Island have been collected and are available for re-appraisal if necessary (King 1984). However, their specific identity is not in question. In contrast, Stokes and Goh (1987) captured and photographed a Pterodroma on North Keeling Island, but did not collect a specimen. They identified this bird as an intermediate morph of the Herald Petrel P.arminjoniana, and believed this bird 'probably belonged to the nominate subspecies known to breed … in the south Atlantic ocean and on Round Island'. In view of the taxonomic uncertainty regarding the 'P. arminjoniana/heraldica' type petrel that occurs on Round Island, and in the absence of a specimen from North Keeling Island, it is therefore impossible to determine the true taxonomic affinity of the Pterodroma species recorded there by Stokes and Goh (1987). Resolution of this matter, assuming the petrel can still be found on North Keeling Island, therefore remains a conservation priority. Until this is confirmed the Round Island Petrel should be considered a vagrant or irregular visitor.

1.3 Distribution

Because they are polymorphic and possess a range of plumages, identification of individuals to specific populations at sea is very difficult. As a result the distribution of both species is not properly understood and movement patterns are poorly known (Marchant and Higgins 1990).

Herald Petrel

The Herald Petrel breeds on Raine Island and possibly other small cays in the Coral Sea, (Garnett and Crowley 2000). However, despite regular surveys of the Herald, Coringa and Magdelaine Cays of the Coral Sea over the last 15 years, Herald Petrels have not been recorded breeding (B.Baker unpublished). The Australian population has been estimated at 25 breeding birds (Garnett and Crowley 2000). There are no estimates of former abundance for the Australian population. Extralimitally, it breeds on a number of other islands in the Pacific Ocean including Easter Island, French Polynesia, the Cook Islands, the Pitcairn group; and the Tonga group (BirdLife 2004; Murphy and Pennoyer 1952). It forages in surrounding waters, mostly south of the equator (Marchant and Higgins 1990).

Round Island Petrel

In Australian territory, the Round Island Petrel possibly breeds on North Keeling Island (Stokes and Goh 1987). Garnett and Crowley (2000) estimated the Australian population to comprise 25 breeding individuals. Extralimitally, this petrel also breeds on Round Island, near Mauritius in the western Indian Ocean, and Trindade Island and Martin Vaz Rocks in the southern Atlantic Ocean. It forages in surrounding waters, mostly south of the equator (Brooke and Rowe 1996; Marchant and Higgins 1990).

There is, however, no data to suggest that that the Round Island Petrel is anything other than either a vagrant to the region or that it has attempted, and failed, to colonise North Keeling Island. It is now nearly 20 years since Stokes and Goh (1987) recorded a small petrel on North Keeling Island and, despite regular visits to the island by Parks Australia North (Commonwealth Dept of Environment and Heritage) staff, it has not been seen since. Breeding has still not been confirmed and intensive searches between May-August in 2002, and June-July in 2003 failed to detect the species (W. Murray and D. Hopton unpublished). Further, the amount of breeding habitat on North Keeling Island suitable for petrels appears extremely restricted and the occurrence of land crabs may be an added deterrent to smaller surface-breeding species (Barry Baker unpublished).

1.4 Population Size and Trend

Garnett and Crowley (2000) assessed Australian populations of the Round Island petrel and Herald petrel as critically endangered. Both species were estimated to have Australian populations of only 25 individuals, and while these populations were considered to be stable, the very restricted geographic distribution of both species was considered precarious for their survival in Australia (Garnett and Crowley 2000). In Australia, the area of occupancy was estimated to be 1km² for the Round Island Petrel, and 2km² for the Herald Petrel.

BirdLife International (2004) recently assessed the global conservation status of the Round Island Petrel as Vulnerable and the Herald Petrel as Least Concern. The global population for Round Island Petrel was estimated to be 2,500-10,000 individuals and for the Herald Petrel, >10,000 individuals.

1.5 Breeding Biology, Ecology and Diet

There are few studies on the breeding biology or ecology of the Herald Petrel and the Round Island Petrel. Table 1.9 provides a summary of known biological information for the two species.

Biological and ecological knowledge has been well summarised by Marchant and Higgins (1990). Perhaps the most valuable breeding studies are those of Gardner et al. (1985) for P. arminjoniana on Round Island, and Brooke (1995) for P. heraldica on the Pitcairn Islands. There is little data available for Australian populations of both species. King (1984) described the nesting site of Herald Petrel on Raine Island. Stokes and Goh (1987) identified the occurrence of Round Island Petrels on North Keeling Island but were unable to confirm breeding was occurring. Both these reports indicate a winter breeding season, accompanied by vocal, diurnal aerial display flights, particularly during the late afternoon. John Cornelius, Environment Protection Agency Queensland, is currently preparing a report updating knowledge for Herald Petrels on Raine Island (Stephen Garnett pers.comm.).

The diet is thought to consist of cephalopods (Marchant and Higgins 1990). Most gadfly petrels are solitary when feeding at sea, capturing prey by swooping down to snatch food by from the sea surface by 'dipping', often pausing on rapidly beating wings to grab items of food (Warham 1990).

1.6 Threats specific to the Herald Petrel and Round Island Petrel

Management of small populations of any organism requires adequate biological and ecological knowledge to ensure appropriate conservation action. As is the case with other species discussed in this paper, there is little relevant biological and ecological data available for both Australian and extralimital populations of the Herald and Round Island Petrels. Table 1.9 highlights these deficiencies. The need to improve biological and ecological knowledge for these species is discussed in Part A where generic recommendations are given to address this deficiency.

Information supporting the listing of Round Island Petrel (DEH website) noted that although North Keeling Island is a National Park, the population was so small that the birds are at risk from the accidental introduction of predators. Herald Petrels breeding on Raine Island would also be similarly threatened by the introduction of alien predators. At this stage, feral predators are not considered an immediate threat to either species as none occur on Raine Island or on North Keeling Island. However, the smaller breeding species of petrels are susceptible to predation by introduced predators (Baker et al. 2002) and appropriate quarantine measures should be put in place at all breeding sites to minimise this threat.

Small populations such as those of the Herald Petrel and Round Island Petrel will always be susceptible to stochastic events such as storms and cyclones. Cyclones have the potential to have serious effects on the vegetation and wildlife of North Keeling Island. A cyclone database maintained by the Bureau of Meteorology shows that a number of cyclones have regularly but unpredictably affected both the Cocos (Keeling) Islands and Raine Island. Such stochastic events are beyond the control of management authorities and cannot be addressed in species recovery plans.

1.7 Issues and Recommendations

• There is taxonomic uncertainty regarding the Pterodroma arminjoniana/heraldica' type petrel that was recorded on North Keeling Island in the 1980s. Further, there have been no records since that time, despite recent attempts to locate birds. Breeding has never been confirmed on North Keeling Island.
• If a species of Pterodroma still occurs on North Keeling Island, collection of genetic material for analysis should be considered a priority, together with collection of a range of morphometric data, to determine its true taxonomic affinity. It should be noted that killing a live bird to achieve taxonomic resolution is not appropriate as non-lethal techniques are available. Until this is confirmed the Round Island Petrel should be considered a vagrant or irregular visitor.
• Should the Round Island Petrel still occur on North Keeling Island, establish whether or not the population is a breeding population and establish appropriate on-going monitoring programs.
• Appropriate quarantine measures should be implemented/maintained by management authorities at North Keeling Island and Raine Island to maintain a barrier to exotic predators.

1.8 References

Baker, G.B., Gales, R., Hamilton, S. & Wilkinson, V. (2002). Albatrosses and petrels in Australia: a review of their conservation status and management. Emu 102: 71-97

BirdLife International. (2004). Threatened birds of the world 2004. CD-ROM. Cambridge, U.K: BirdLife International.

Brooke, M. de L. and Rowe, G. (1996). Behavioural and molecular evidence for specific status of dark and light morphs of the Herald Petrel Pterodroma heraldica. Ibis 138: 420-432. 1996

Brooke, M. de L. (1995). The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls. Biol.Journal Linn. Soc.

Brooke, M. de L. (2004). Albatrosses and petrels across the world. Oxford University Press, Oxford.

Brooke, M. de L., Imber, M.J. and Rowe, G. (2000). The occurrence of two surface-breeding species of Pterodroma on Round Island, Indian Ocean. Ibis 142: 154-158.

Burger, J. and Gochfeld, M. (1991). Nest-site selection by the Herald Petrel and White-tailed tropicbird on Round Island, Indian Ocean, Wilson Bull. 103: 126-130.

Da Silva, G.L. (1995). Aspectos da biologia reprodutiva de Pterodroma arminjoniana (Giglioli & Salvadori, 1869) (Aves, Procellariidae) na Ilha de Trindade, Atlantico Sul. Unpublished MSc thesis, Museu Nacional - UFRJ, Rio de Janeiro.

DEH Website. www.deh.gov.au/biodiversity/threatened/information/factsheets/round-island-petrel.html

Gardner, A.S., Duck, C.D. & Greig, S. (1985). Breeding of the Trindade Petrel, Pterodroma arminjoniana on Round Island, Mauritius. Ibis 127: 517-522.

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

Gill, F.B., Jouanin, C. & Storer, R.W. (1970). Notes on the seabirds of Round Island, Mauritius. Auk 87: 514-521

Harrison, P. (1983). Seabirds: An identification guide. Sydney: Reed

Imber, M.J. (1985). Origins, phylogeny and taxonomy of the glad-fly petrels, Pterodroma spp. Ibis 127: 197-229

Imber, M.J., Jolly, J.N., Brooke, M. de L. (1995). Food of three sympatric gad-fly petrels (Pterodroma species) breeding on the Pitcairn Islands. Biological Journal of Linnean Society 56:233-240.

King, B.R. (1984). The Herald Petrel Pterodroma armonjoniana breeding on Raine Island. Emu 84:246-247.

Kuroda, N. (1986). On the intestinal twistings in gadfly-petrels and comparative notes on the digestive tract in Procellariiformes. Japanese Journal of Ornithology 35: 1-14.

Marchant, S. and Higgins, P.J. (eds). (1990). The Handbook of Australian, New Zealand and Antarctic Birds. Volume 1. Oxford University Press, Melbourne.

Murphy, P.C and Pennoyer, J.M. (1952). Larger petrels of the genus Pterodroma. American Museum Novitates 1580: 1-43.

Nelson, B. (1980). Seabirds their biology and ecology. Hamlyn: London.

Stokes, T. and Goh, P. (1987). Records of Herald Petrels and the Christmas Island Frigatebird from North Keeling Island, Indian Ocean. Australian Bird Watcher 12:132-133.

Vinson, J.M. (1976). Notes sur les procellariens de I'lle Ronde. Oiseau Rev.Fr.Ornithol. 46: 1-24.

Warham J. (1990). The petrels: Their ecology and breeding systems. Academic Press: London.

Warham J. (1996). The behaviour, population biology and physiology of the petrels. Academic Press: London.