Acrocephalus luscinius

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	SYLVIIDAE

Scientific Name:

Acrocephalus luscinius

Species Authority:

(Quoy & Gaimard, 1830)

Common Name/s:

English

–

Nightingale Reed-warbler, Nightingale Reed Warbler, Nightingale Reed-Warbler

Assessment Information [top]

Red List Category & Criteria:

Critically Endangered A3bce+4bce ver 3.1

Year Published:

2010

Assessor/s:

BirdLife International

Reviewer/s:

Calvert, R., Symes, A., Butchart, S.

Contributor/s:

Saunders, A., Camp, R., Freifeld, H., Dutson, G.

Justification:
This species qualifies as Critically Endangered because the very rapid rate of decline in its very small global population observed over the past three generations is expected to increase owing to habitat loss and degradation combined with the impact of brown tree snake Boiga irregularis on Saipan; this snake has already led to the reed-warbler's extirpation from Guam.

History:

2009	–	Critically Endangered
2008	–	Endangered
2004	–	Endangered
2000	–	Endangered
1996	–	Vulnerable
1994	–	Vulnerable

Geographic Range [top]

Range Description:	This species is historically known from Guam (to USA), Saipan, Alamagan, Aguijan and Pagan in the Northern Mariana Islands (to USA). It was extirpated from Guam in the late 1960s, and from Pagan before 1981. A tiny population perhaps survives on uninhabited Aguijan (1-6 birds) and on Alamagan (c.346), but the majority of the population occurs on Saipan. Abundance (density times the area of Saipan, 115.39 km²) with 95% Confidence Intervals declined from 6,658 birds (5,331-8,054) in 1982 down to 4,639 (3,669-5,689) birds in 1997, and has continued to decline to 2,742 birds (1,686-3,956) in the 2007 survey⁹. This represents a 59% decline in the species since 1982. Over three generations this equates to an overall population decline of 47%, but this rate of decline has been increasing such that the rate recorded between 1997 and 2007 corresponds to a three generation decline of 60%. The rapid human expansion on Saipan in the 1990s has slowed but the U.S. military is expanding its presence and operations which will likely lead to further habitat conversion and degradation. Furthermore, there is evidence that the brown tree snake Boiga irregularis has become established on Saipan. This is cause for concern given the catastrophic declines it caused on Guam's birds. The combination of these two drivers is expected to lead to projected declines above 80% over 3 generations in the future.
Countries:	Native: Northern Mariana Islands
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	Three island populations exist: Aguijan (1-6 birds), Alamagan (c.346) and Saipan (2,742 estimated from surveys in 2007 - Camp et al. 2009). This equates to a global population of c. 3,100 individuals. However, given the rapid decline occurring on Saipan and that a proportion of the population will be immature birds this is cautiously interpreted as 2,000-2,499 mature individuals.
Population Trend:	Decreasing

Habitat and Ecology [top]

Habitat and Ecology:	On Saipan, it occurs in thicket-meadow mosaics, forest edge, reed-marshes and forest openings¹. A recent study on Saipan found nests in upland introduced tangantangan forest, a native mangrove wetland and a native reed wetland⁵. On Alamagan, it inhabits open forest with brushy understorey and wooded edges adjacent to open grassland. On Aguijan, it inhabits formerly disturbed areas vegetated by groves of trees and thickets. On Guam and Pagan, it was almost exclusively found in freshwater wetland and wetland edge vegetation^2,3,4.
Systems:	Terrestrial; Freshwater

Habitat and Ecology:

On Saipan, it occurs in thicket-meadow mosaics, forest edge, reed-marshes and forest openings¹. A recent study on Saipan found nests in upland introduced tangantangan forest, a native mangrove wetland and a native reed wetland⁵. On Alamagan, it inhabits open forest with brushy understorey and wooded edges adjacent to open grassland. On Aguijan, it inhabits formerly disturbed areas vegetated by groves of trees and thickets. On Guam and Pagan, it was almost exclusively found in freshwater wetland and wetland edge vegetation^2,3,4.

Systems:

Terrestrial; Freshwater

Threats [top]

Major Threat(s):	On Guam, several factors in combination are likely to have caused the species's extirpation, including wetland destruction, predation by the introduced brown tree snake Boiga irregularis, pesticide-use and major fires. On Saipan, available habitat has been reduced for agriculture, home-building and tourist-related facilities. The brown tree snake is now understood to be established on Saipan and unless it can be controlled the population is likely to be extirpated rapidly once snake numbers have reached the point where they impact bird populations. On Aguijan, feral goats severely degrade habitats⁶. Introduced predators, including monitor lizard Varanus indicus, feral cats and rats Rattus spp., may be a large factor in the reported high proportion of nest failures⁴.

Major Threat(s):

On Guam, several factors in combination are likely to have caused the species's extirpation, including wetland destruction, predation by the introduced brown tree snake Boiga irregularis, pesticide-use and major fires. On Saipan, available habitat has been reduced for agriculture, home-building and tourist-related facilities. The brown tree snake is now understood to be established on Saipan and unless it can be controlled the population is likely to be extirpated rapidly once snake numbers have reached the point where they impact bird populations. On Aguijan, feral goats severely degrade habitats⁶. Introduced predators, including monitor lizard Varanus indicus, feral cats and rats Rattus spp., may be a large factor in the reported high proportion of nest failures⁴.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway A recovery plan exists but there has been little or no active management for the species to date. However, provisions to protect habitat and mitigate loss have generally been included in major land development projects. In 1989, a goat removal programme was begun on Aguijan but, by 1995, goat populations had begun to rebound with reduced hunting pressure. Trap lines for snakes are maintained at ports, night searches are conducted and a sniffer dog programme has recently been established. Publicity campaigns aim to raise the general awareness of island residents, including port workers, about the dangers of snake colonisation⁴. Repeat surveys have been conducted on Saipan in 1982, 1997 and 2007. Conservation Actions Proposed Monitor the populations on all three islands⁴. Protect Aguijan, and especially Alamagan from snake colonisation⁴. Control feral ungulates and predators including B. irregularis⁴. Identify and protect essential habitat⁴. Conduct basic research, e.g. on population dynamics and validity of subspecies, to assist in appropriate recovery efforts⁴. Establish additional populations on other islands⁴. Clarify the status of B. irregularis on Saipan and mitigate the potential effects should its number increase.

Conservation Actions:

Conservation Actions Underway
A recovery plan exists but there has been little or no active management for the species to date. However, provisions to protect habitat and mitigate loss have generally been included in major land development projects. In 1989, a goat removal programme was begun on Aguijan but, by 1995, goat populations had begun to rebound with reduced hunting pressure. Trap lines for snakes are maintained at ports, night searches are conducted and a sniffer dog programme has recently been established. Publicity campaigns aim to raise the general awareness of island residents, including port workers, about the dangers of snake colonisation⁴. Repeat surveys have been conducted on Saipan in 1982, 1997 and 2007.

Conservation Actions Proposed
Monitor the populations on all three islands⁴. Protect Aguijan, and especially Alamagan from snake colonisation⁴. Control feral ungulates and predators including B. irregularis⁴. Identify and protect essential habitat⁴. Conduct basic research, e.g. on population dynamics and validity of subspecies, to assist in appropriate recovery efforts⁴. Establish additional populations on other islands⁴. Clarify the status of B. irregularis on Saipan and mitigate the potential effects should its number increase.

Bibliography [top]

	Camp, R. J. 2008. Trends in bird populations on Saipan. Camp, R. J.; Pratt, T. K.; Marshall, A. P.; Amidon, F.; Williams, L. L. 2009. Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler (Acrocephalus luscinia). Bird Conservation International 19(4): 323-337. 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. Mosher, S.M. and Fancy, S.G. 2002. Description of nests, eggs, and nestlings of the endangered nightingale reed-warbler on Saipan, Micronesia. Wilson Bulletin 114(1): 1-10. Reichel, J. D.; Wiles, G. J.; Glass, P. O. 1992. Island extinctions: the case of the endangered Nightingale Reed-warbler. Wilson Bulletin 104: 44-54. U. S. Fish and Wildlife Service. 1998. Recovery plan for the Nightingale Reed-warbler Acrocephalus luscinia.

Camp, R. J. 2008. Trends in bird populations on Saipan.

Camp, R. J.; Pratt, T. K.; Marshall, A. P.; Amidon, F.; Williams, L. L. 2009. Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler (Acrocephalus luscinia). Bird Conservation International 19(4): 323-337.

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.

Mosher, S.M. and Fancy, S.G. 2002. Description of nests, eggs, and nestlings of the endangered nightingale reed-warbler on Saipan, Micronesia. Wilson Bulletin 114(1): 1-10.

Reichel, J. D.; Wiles, G. J.; Glass, P. O. 1992. Island extinctions: the case of the endangered Nightingale Reed-warbler. Wilson Bulletin 104: 44-54.

U. S. Fish and Wildlife Service. 1998. Recovery plan for the Nightingale Reed-warbler Acrocephalus luscinia.

Citation:	BirdLife International 2010. Acrocephalus luscinius. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 22 May 2012.
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