Zosterops tenuirostris 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Zosteropidae

Scientific Name: Zosterops tenuirostris Gould, 1837
Common Name(s):
English Slender-billed White-eye
Taxonomic Source(s): Christidis, L. and Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Australia.
Identification information: 13-14 cm. Medium-sized, warbler-like bird with long, slightly decurved bill. Sexes similar. Greyish-brown upperparts, including head and flanks, with olive cast. White eye-ring. Black lores. Suffused olive-yellow upperwing-coverts. Yellow-tinged undertail-coverts. Grey bill, paler lower mandible. Similar spp. Silvereye Z. lateralis is grey on back and chest, has shorter, straighter bill, is less yellow overall. White-chested White-eye Z. albogularis is larger with white underparts. Voice High-pitched. Wheezier and more sibilant than Z. lateralis. Hints Tends to forage on branches and bark more than Z. lateralis.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Christian, M., Garnett, S., Holdaway, R. & Ward, R.
Facilitator/Compiler(s): Ekstrom, J., Garnett, S., McClellan, R., Symes, A. & Taylor, J.
This species is listed as Near Threatened because although it has a very small range and population on a single island (and has declined historically), its population is estimated to have been stable for several decades. It has not been significantly affected by introduced predators, including rats, and therefore there is not thought to be any plausible threat likely to lead to very rapid future declines. If such a plausible future threat were to be identified it would warrant classification as Vulnerable.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Zosterops tenuirostris is found on Norfolk Island (to Australia), where it is thought to number c.4,500 mature individuals. The species is mostly restricted to the Norfolk Island National Park but is also found in the botanic garden and One Hundred Acres Reserve (M. Christian pers comms. 2016). It underwent declines since the 1960s, particularly outside the park, which continued in the period 1987-1997, however numbers since appear to have stabilised.

Countries occurrence:
Norfolk Island
Additional data:
Estimated area of occupancy (AOO) - km2:8Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:27
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:2-5Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:A survey in 2010 estimated a population of c.4,000 birds in the National Park on the basis of 74 records in point counts at a density of c.900/km2; the total population has therefore been estimated at 4,500 mature individuals (Dutson 2013, Garnett et al. 2011).

Trend Justification:  The species has been declining since the 1960s, particularly outside the Norfolk Island National Park, a decline which has continued in the period from 1987 to 1997 (Garnett and Crowley 2000). Numbers are since thought to have stabilised, as a 2010 survey found detected similar numbers along transects to previous surveys (Garnett et al. 2011).
Current Population Trend:Stable
Additional data:
Number of mature individuals:4500Continuing decline of mature individuals:No
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:It lives in rainforest and tall secondary growth. It uses its long, down-curved bill to probe fissures in bark for insects, although it also takes fruit, including those of exotic species. It is also observed feeding on nectar from flowers of the endemic Pittosporum bracteolatum (M. Christian in litt. 2007). It forages in parties and appears to have a different ecological niche to that of the self-introduced Silvereye Z. lateralis

Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):3.5
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): The species has gradually disappeared from all parts of the island that have been extensively cleared for timber, cultivation, pasture and continued development (M. Christian in litt. 2007). This species is also presently threatened by the replacement of cleared native forest with invasive weeds (M. Christian in litt. 2007). Its decline was probably exacerbated by the arrival of black rat Rattus rattus. Cats are opportunistic predators of adult birds (R. Ward in litt. 2007).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
The Norfolk Island National Park was declared in 1986, encompassing most of the main remaining stands of native trees on the island. Rat baiting and cat trapping is carried out within its boundaries. In 2006, it was noted that control measures for rats were budget-constrained and limited in their effectiveness (S. Garnett in litt. 2006). Responsible cat ownership is being encouraged, through sponsorship of a cat neutering clinic. The Norfolk Island Region Threatened Species Recovery Plan (Director of National Parks 2010) recommends a set of recovery measures required to reduce or remove threats to native species on the island. Rabbits have been removed from Phillip Island.

Conservation Actions Proposed
Monitor trends in the population through analysis of birdwatchers' records. Consider introducing the species to Phillip Island. Eliminate mammalian predators from areas in which there is strong community support (M. Christian pers comms 2016), and prevent reintroduction (Director of National Parks 2010). Carry out research into the impacts of introduced predators (M. Christian in litt. 2007). The idea of installing a predator-proof fence around the national park, Hundred Acre Reserve and other important areas of habitat was once proposed but hasn't gained traction, likely due to the costs and maintenance this would involve (M. Christian pers comms. 2016).

Citation: BirdLife International. 2016. Zosterops tenuirostris. The IUCN Red List of Threatened Species 2016: e.T22714226A95227692. . Downloaded on 21 August 2018.
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