Ten Seabird species Issues paper

Department of the Environment and Heritage, May 2005
ISBN 0 6425 5005 0

Part B: Conservation Issues For Specific Species/Groups (continued)

5. Australian Lesser Noddy - Conservation issues

Australian lesser Noddy Anous tenuirostris melanops
Conservation Status Endemic Species
BirdLife International Status Least Concern
EPBC Status Vulnerable

5.1 General Introduction

The Sterninae, a sub-family of the Laridae, comprises the terns and noddies, a cosmopolitan group of seabirds, with narrow pointed wings and long pointed bills, They are mostly slimmer, longer-tailed and more aerial than gulls. The sub-family comprises about 42 species in seven genera.

The Australian lesser noddy Anous tenuirostris is a small dark-plumaged, tropical tern (length 29-34 cm, wingspan 57-64 cm) with a long slender straight bill, long narrow wings and slightly wedge-shaped tail. It is confined to the tropical and sub-tropical Indian Ocean. The Australian subspecies of the Australian lesser noddy A. T. melanops breeds only on three islands in the Houtman Abrolhos, off Western Australia, where it nests in mangrove trees. Typical adults are dark brown with a diffuse pale grey cap. The sexes are similar and there is no seasonal variation in plumage (Higgins and Davies 1996, Surman and Wooller 1995).

5.2 Taxonomy

There are few taxonomic issues associated with this species. The Australian lesser noddy is sometimes considered conspecific with black noddy, Anous minutus, which occurs in the Pacific and Atlantic Oceans (Higgins and Davies 1996).

5.3 Distribution

Anous tenuirostris melanops is only known to breed in Houtman Abrolhos, where colonies on Pelsaert, Wooded and Morley Islands occupy a total of 5 ha. Birds appear to remain near the breeding islands all year (Higgins and Davies 1996). A population thought to be A.t.melanops possibly breeds in the Ashmore Reef, however the subspecific identity has not been confirmed (Stokes and Hinchey 1990).

Nominate tenuirostris breeds extralimitally in the tropical and subtropical Indian Ocean at the Seychelles, Cargados Carajos Shoal, Reunion I, Agalengas I, Chagos Archipelago and the Maldives (Higgins and Davies 1996).

The oceanic range of the Australian Lesser Noddy is largely unknown. They may be mostly sedentary, returning to breeding islands to roost during non-breeding season. They possibly leave the islands for short periods and the feeding range from islands is probably extensive. Gales can displace birds many hundreds of kms (Higgins and Davies 1996; Harrison 1983).

5.4 Population size and trend

Although numbers vary considerably among years and colonies, the population is considered to be stable (Garnett and Crowley 2000). Total numbers early in the 20th century were possibly as low as 20,000 pairs (Burbidge and Fuller 1989, Johnstone and Storr 1998). Guano mining during the 19th century and early 20th century coincided with the disappearance of birds from Pelsaert Island sometime between 1899 and 1907 (Burbidge and Fuller 1981). Colonies re-established sometime between 1913 and 1936 (Fuller and Burbidge 1992). Fluctuations in abundance of their prey species may explain the variation in breeding numbers (Garnett and Crowley 2000). Breeding colonies on Pelsaert, Wooded and Morley Islands have been observed since the early 19th century and records are summarised by Higgins and Davies (1996).

Garnett and Crowley (2000) assessed Australian populations of the Lesser Noddy as vulnerable. The population was estimated to be 100,000 breeding birds, and while the population was considered to be stable, the very tiny area in which this subspecies breeds could be badly affected by catastrophic events (Garnett and Crowley 2000). The area of occupancy was estimated to be 3km2.

BirdLife International (2004) recently assessed the global conservation status Anous tenuirostris at the species level as Least Concern. This species has a large range, and the global population was estimated to be 1,200,000 individuals.

5.5 Breeding Biology, Ecology and Diet

Table 5.9 provides a summary of known biological information for the subspecies.

Biological and ecological knowledge has been summarised by Higgins and Davies (1996). The Australian lesser noddy represents one of only three marine terns to build substantial nests. On Houtman Abrolhos, Australian lesser noddies breed in dense clumps of mangrove up to 4m tall. Nests are constructed of seaweed Ulva lactuca, gathered from the surrounding sea and lagoons, held together by excreta and placed in the fork of a mangrove (Johnstone and Coate 1992). On Ashmore Reef, birds possibly of this species were thought to be nesting in low bushes of Sesbania Pea Sesbania cannibina (Stokes and Hinchey 1990). Australian lesser noddies nest colonially, and move colonies periodically because nesting birds retard tree growth, resulting in tree death (Higgins and Davies 1996).

A detailed breeding biology study on Pelsaert Island was carried out by Surman and Wooller (1995). Breeding success there was found to be 47% with the main determinant of breeding success being site selection. Sites protected from strong WNW winds were more likely to succeed than exposed nests, with storms causing extensive egg loss from the more exposed nests. On Pelsaert Island egg laying occurred from late August to early December with a peak in September. The first eggs hatched at the end of September. Other studies show egg laying from August through to March or early April (Higgins and Davies 1996).

The foraging habitat of Australian lesser noddies is virtually unknown. They feed by 'dipping', taking prey from or just below the surface of water without alighting. They may forage out to sea or close inshore to breeding islands, including outside fringing reefs, feeding on small squid and fish (Higgins and Davies 1996). They roost mainly in mangroves, and sometimes rest on the beaches.

5.6 Threats specific to the Australian lesser noddy

The Australian lesser noddy at present faces few threats to its survival in the Houtman Abrolhos. Garnett and Crowley (2000) estimated the population to comprise 100,000 breeding birds, and although inter-annual variation in breeding is apparent, they considered the population to be stable.

There is very little evidence of human interference, although the islands are often visited by fishing parties, yacht crews and groups of naturalists (Johnstone 1992, Johnstone and Croate 1992) Camping on Pelsaert Island is prohibited except by permit and disturbance caused by humans is minimal at present (Fuller and Burbidge 1992). The Fisheries Management Paper No 117 (Department of Fisheries 2002) considers wildfire as a risk to the Houtman Abrolhos but it is unlikely that mangroves would be significantly affected by fire.

A number of exotic plant and animal species have been introduced to the Houtman Albrolhos islands. Feral animals known to have occurred on the islands include rabbits, rats and cats. A successful black rat and cat eradication program was carried out in the Easter Group. Ongoing African boxthorn eradication programs occur on the islands in the Southern Group. The Fisheries Management Paper No 117 (Department of Fisheries 2002) recommends surveys of exotic plants and animals on the Albrolhos Islands to establish the species present and to develop a plan for their removal or management. It also recommends the preparation and implementation of a management plan for preventing the arrival of exotic flora and fauna.

The following potential threats are listed by Garnett and Crowley (2000):

  • catastrophic destruction by cyclones
  • pollution from oil spills that could damage birds and mangroves
  • sea level rises associated with global warming affecting the mangroves required for breeding
  • commercial fishing potentially affecting food supplies

5.7 Issues and Recommendations

  • The existence of Australian lesser noddies at Ashmore reef requires confirmation.
  • Should Australian lesser noddies still occur at Ashmore Reef, establish their taxonomic affinity, and whether or not breeding occurs. All colonies should be managed in such a way that human disturbance is minimised.
  • Maintain monitoring and management of breeding islands at Houtman Abrolhos.
  • Implement the recommendations of the Fisheries Management Paper No.117 (Department of Fisheries 2002) in relation to exotic plant and feral animal control and quarantine procedures to prevent introduction of exotic plants and animals.

5.8 References

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

Burbidge A. A. and Fuller, P. J. (1989) Numbers of breeding seabirds on Palsaert Island, Houtman Abrolhos, Western Australia, Corella 13: 57-61

Burbidge A. A. and Fuller, P. J. (1991) A million seabirds, Landscape, 6: 17-23

Department of Fisheries (2002) Fisheries Management Paper No 117, Management of the Houtman Albolhos System, December 1998

Fuller, P. J., Burbidge A. A. and Owens R. (1994) Breeding seabirds of Houtman Abrolhos, Western Australia: 1991-1993, Corella 18:97-113.

Fuller, P.J. and Burbidge, A.A. (1992). Seabird Islands No. 215. Pelsaert Island, Houtman Abrolhos, Western Australia. Corella 16:47-57.

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

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

Higgins, P.J. & Davies, S.J.J.F. (eds). (1996). The Handbook of Australian, New Zealand and Antarctic Birds. Volume 3. Oxford University Press, Melbourne.

Johnstone, R.E (1992). Seabird Islands No. 217. Morley Island, Easter Group, Houtman Abrolhos, Western Australia. Corella 16:160-162.

Johnstone, R.E & Coate, K. (1992). Seabird Islands No. 216. Wooded Island, Easter Group, Houtman Abrolhos, Western Australia. Corella 16:155-159.

Stokes , T. and Hinchey, M. (1990) Which small noddies breed at Ashmore Reef in the indian Ocean? Emu 90: 269-271

Surman, C.A. and Wooller, R.D. (1995) The Breeding biology of the Lesser Noddy on Palsaert Island, Western Australia, Emu 95: 47-53

Table 5.9: Summary of biological information for Australian lesser noddies
 
Australian Lesser noddy
Refs
Common name Australian lesser noddy
 
Scientific name Anous tenuiriostris melanops
Conservation status
- Australia EPBC
- BirdLife Int.

Vulnerable
Least Concern

B
A
Australian breeding localities Houtman Albrolhos - colonies known on Pelseart Is., Wooded Is. and Morley Is.
B, D
Extra-limital breeding localities Only known to breed in Australian localities listed above.
B
Foraging localities Foraging habitat is virtually unknown. They may forage out to sea or in seas close to breeding islands, including outside fringing reefs
C, D
Annual breeding pairs
- Aust populations
- Global


100,000 breeding birds
100,000 breeding birds


B
Australian % of global population 100%
B
Breeding frequency
(annual/biennial)
Annual
C
Clutch size One
C, D
Breeding success
- % chicks fledged from eggs laid
47% - Pelsaert Island study
D
Age at first breeding Possibly 3-4 years.
C
Juvenile survival Unkown
 
Adult survival Unknown
 
Nest site Builds nests in White Mangroves Avicennia marina, which occur in small scattered patches on a few islands of the Houtman Albrolhos. Nesting colonies move periodically because nesting birds retard tree growth and sometimes kill trees.
B
Nesting behaviour
(colonial / dispersed pairs)
Colonial
B
Breeding season Spring and through summer
C, D
Food / Foraging Feed by 'dipping', taking prey from or just below the surface of water without alighting. Feeds on small squid and fish in nearby waters.
B, C
Refs: A - BirdLife International 2004; B - Garnett and Crowley 2000; C - Higgins and Davies 1996; D - Surman and Wooller 1995.