Zosterops conspicillatus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Bibliography

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	PASSERIFORMES	ZOSTEROPIDAE

Scientific Name:

Zosterops conspicillatus

Species Authority:

(Kittlitz, 1832)

Common Name/s:

English

–

Bridled White-eye

Assessment Information [top]

Red List Category & Criteria:

Endangered A3e;B1ab(v) ver 3.1

Year Published:

2008

Assessor/s:

BirdLife International

Reviewer/s:

Mahood, S., Butchart, S.

Contributor/s:

Saunders, A., Hawley, N., Amidon, F., Lepson, J.

Justification:
This species is restricted to three very small islands and is currently abundant. However, it is projected to undergo a very rapid population decline owing to the recent establishment of brown tree-snake Boiga irregularis on Saipan. It therefore qualifies as Endangered.

History:

2004	–	Endangered
1994	–	Not Recognized
1988	–	Not Recognized

Geographic Range [top]

Range Description:	Zosterops conspicillatus is restricted to the Northern Mariana Islands (to USA) where it occurs on the islands of Saipan, Tinian and Aguijan. It is very abundant and, on Saipan, is estimated to occur at a population density of approximately 5,950 individuals/km² ³. This very high density suggests that the species exists at the maximum density allowed by resources available in the habitat and the total population is likely to number in excess of 100,000, and is perhaps as high as 200,000. A similarly sized population probably exists on Tinian, and in 2002, the population estimated for the island of Aguijan was 18,576 individuals¹⁰. It is more abundant in native limestone forest (c. 5,950 birds/km²) than in disturbed habitats (c. 4,000 birds/km²)³.
Countries:	Native: Northern Mariana Islands
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	Craig (1996) estimated a population size of approximately 5,950 in limestone forest and of 4,000 in disturbed sites during surveys conducted in 1991 and 1992. Native habitats (including limestone forest) cover approximately 30% on the island. Thus a total population estimate on Saipan is likely to be of the order of 200,000. A similarly sized population probably exists on Tinian and the total population count would therefore be in the band 100,000 to 499,000. In 2002, the population estimated for the island of Aguijan was 18,576 individuals (Esselstyn et al. 2002).
Population Trend:	Decreasing

Population:

Craig (1996) estimated a population size of approximately 5,950 in limestone forest and of 4,000 in disturbed sites during surveys conducted in 1991 and 1992. Native habitats (including limestone forest) cover approximately 30% on the island. Thus a total population estimate on Saipan is likely to be of the order of 200,000. A similarly sized population probably exists on Tinian and the total population count would therefore be in the band 100,000 to 499,000. In 2002, the population estimated for the island of Aguijan was 18,576 individuals (Esselstyn et al. 2002).

Population Trend:

Decreasing

Habitat and Ecology [top]

Habitat and Ecology:	The species is found in a wide range of habitats from native limestone forest to scrubby secondary growth of disturbed habitats and even urban areas. It is less common in swordgrass savannah³. It commonly forages in large flocks in the upper canopy of native limestone forest, but also feeds in other habitats⁴. Its food consists of insects, seeds, fruits, caterpillars and berries and it is not strongly nectarivorous⁴. It seemingly competes for food with the larger, dominant Golden White-Eye Cleptornis marchei, probably because of the extremely high densities³. Breeding occurs in January, February and August, October; though on Saipan there is a distinct peak in February/March^3,11. It nests predominately in Leucaena leucocephala thickets¹¹. It is not territorial but birds remain in the home range³.
Systems:	Terrestrial

Habitat and Ecology:

The species is found in a wide range of habitats from native limestone forest to scrubby secondary growth of disturbed habitats and even urban areas. It is less common in swordgrass savannah³. It commonly forages in large flocks in the upper canopy of native limestone forest, but also feeds in other habitats⁴. Its food consists of insects, seeds, fruits, caterpillars and berries and it is not strongly nectarivorous⁴. It seemingly competes for food with the larger, dominant Golden White-Eye Cleptornis marchei, probably because of the extremely high densities³. Breeding occurs in January, February and August, October; though on Saipan there is a distinct peak in February/March^3,11. It nests predominately in Leucaena leucocephala thickets¹¹. It is not territorial but birds remain in the home range³.

Systems:

Terrestrial

Threats [top]

Major Threat(s):	The biggest threat on Saipan comes from the now well-established population of brown tree snake Boiga irregularis^5,8. The snake has already caused the extinction of the nominate subspecies from Guam⁶ and unless it can be controlled, the population is likely to be extirpated rapidly, even though it is currently abundant. The proposed development of Tinian for military training¹⁴ and tourism requires the importation of large amounts of building materials and increases the likelihood of accidental introduction of brown tree snake⁷.

Major Threat(s):

The biggest threat on Saipan comes from the now well-established population of brown tree snake Boiga irregularis^5,8. The snake has already caused the extinction of the nominate subspecies from Guam⁶ and unless it can be controlled, the population is likely to be extirpated rapidly, even though it is currently abundant. The proposed development of Tinian for military training¹⁴ and tourism requires the importation of large amounts of building materials and increases the likelihood of accidental introduction of brown tree snake⁷.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway A feasibility study completed in 2006 revealed that Sarigan island (5km²) would be a suitable site for a benign introduction⁹, a conservation introduction plan is currently under development and the first birds should be transferred in Spring 2008¹³. A brown tree-snake barrier is also under construction at the port on Tinian to support interdiction efforts on the island¹². Conservation Actions Proposed Implement stringent measures such as traps and monitors to prevent the spread of B. irregularis onto Tinian, particularly around the airport and the harbour⁷. Avoid introduction of B. irregularis onto Aguijan. Control the spread of B. irregularis on Saipan. Continuously monitor the population on Saipan. Implement the benign introduction of the species to Sarigan.

Conservation Actions:

Conservation Actions Underway
A feasibility study completed in 2006 revealed that Sarigan island (5km²) would be a suitable site for a benign introduction⁹, a conservation introduction plan is currently under development and the first birds should be transferred in Spring 2008¹³. A brown tree-snake barrier is also under construction at the port on Tinian to support interdiction efforts on the island¹².

Conservation Actions Proposed
Implement stringent measures such as traps and monitors to prevent the spread of B. irregularis onto Tinian, particularly around the airport and the harbour⁷. Avoid introduction of B. irregularis onto Aguijan. Control the spread of B. irregularis on Saipan. Continuously monitor the population on Saipan. Implement the benign introduction of the species to Sarigan.

Bibliography [top]

	Craig, R. J. 1996. Seasonal population surveys and natural history of a Micronesian bird community. Wilson Bulletin 108: 246-267. Engbring, J.; Ramsey, F. L.; Wildman, V. J. 1982. Micronesian forest bird survey, 1982: Saipan, Tinian, Agiguan, and Rota. U.S. Fish and Wildlife Service, Honolulu. Esselstyn, J., J. B. Cruz, L.L. Williams, and N. Hawley. 2003. Wildlife and vegetation surveys: Aguiguan 2002. Martin, G.; Kremer, S. 2006. Saving Saipan's White-eye. Endangered Species Bulletin: 38-41. Sachtleben, T. 2005. Predation and nest success of forest birds in native and non-native habitat on Saipan, Mariana Islands. M.Sc. Thesis, Colorado State University. Savidge, J. A. 1987. Extinction of an island forest avifauna by an introduced snake. Ecology 68: 660-668. U.S. Department of Defense. 2007. Defense representative Guam, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia and Republic of Palau; notice of intent to prepare an environmental impact statement/overseas environmental impact statement for the Mariana…. Federal Register 72: 30557-30559. Williams, S. 2004. Endangered and threatened wildlife and plants; Endangered Status for the Rota Bridled White-Eye (Zosterops rotensis) from the commonwealth of the Northern Mariana Islands. Federal Register 69(14): 3022-3029.

Craig, R. J. 1996. Seasonal population surveys and natural history of a Micronesian bird community. Wilson Bulletin 108: 246-267.

Engbring, J.; Ramsey, F. L.; Wildman, V. J. 1982. Micronesian forest bird survey, 1982: Saipan, Tinian, Agiguan, and Rota. U.S. Fish and Wildlife Service, Honolulu.

Esselstyn, J., J. B. Cruz, L.L. Williams, and N. Hawley. 2003. Wildlife and vegetation surveys: Aguiguan 2002.

Martin, G.; Kremer, S. 2006. Saving Saipan's White-eye. Endangered Species Bulletin: 38-41.

Sachtleben, T. 2005. Predation and nest success of forest birds in native and non-native habitat on Saipan, Mariana Islands. M.Sc. Thesis, Colorado State University.

Savidge, J. A. 1987. Extinction of an island forest avifauna by an introduced snake. Ecology 68: 660-668.

U.S. Department of Defense. 2007. Defense representative Guam, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia and Republic of Palau; notice of intent to prepare an environmental impact statement/overseas environmental impact statement for the Mariana…. Federal Register 72: 30557-30559.

Williams, S. 2004. Endangered and threatened wildlife and plants; Endangered Status for the Rota Bridled White-Eye (Zosterops rotensis) from the commonwealth of the Northern Mariana Islands. Federal Register 69(14): 3022-3029.

Citation:	BirdLife International 2008. Zosterops conspicillatus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 24 May 2012.
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