Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Sylviidae

Scientific Name: Phylloscopus ijimae
Species Authority: (Stejneger, 1882)
Common Name(s):
English Izu Leaf-warbler, Ijima's Leaf-Warbler, Ijima's Leaf Warbler
Identification information: 10-12 cm. Small, stocky, warbler. Bright olive-green above and white below with a lemon-yellow wash on vent. Long, whitish supercilium with lemon yellow centre; white orbital, split by dark olive-green eye-stripe and lore. Slightly mottled ear-coverts and cheeks. Single whitish wing-bar in most birds. Faint greyish wash to sides of breast and flanks. Yellowish undertail-coverts. pinkish legs and feet; bill dark above, strong yellow below to tip. Similar spp. Arctic Warbler P. borealis is larger, stockier, has yellowish supercilium, cheeks and underparts. Voice A short, bright, "silvery" swee-swee-swee-swee, and sometimes a slower more disyllabic suwee-suwee-suwee-suwee. Call a loud huee, with a downward inflection.

Assessment Information [top]

Red List Category & Criteria: Vulnerable C2a(ii) ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Crystal, F., Allen, D. & Odaya, Y.
Facilitator/Compiler(s): Benstead, P., Gilroy, J., Taylor, J., Allinson, T
This warbler qualifies as Vulnerable because it has a small, declining and fragmented population as a result of habitat loss, potentially compounded by pesticide use and trapping during migration.

Previously published Red List assessments:
2008 Vulnerable (VU)
2007 Vulnerable (VU)
2004 Vulnerable (VU)
2000 Vulnerable (VU)
1996 Vulnerable (VU)
1994 Vulnerable (VU)
1988 Lower Risk/least concern (LR/lc)

Geographic Range [top]

Range Description: Phylloscopus ijimae is endemic to Japan (BirdLife International 2001). It breeds on the Izu Islands, between Oshima and Aogashima, and was recently discovered nesting on Nakano-shima in the Tokara Islands. There are non-breeding/passage records from Honshu, Kyushu and the Nansei Shoto Islands, where it probably winters. It is also reportedly a regular migrant on the Osumi peninsula in Kagoshima ken (F. Crystal in litt. 2005) and Wakayama-ken (Y. Odaya in litt. 2012). It may also winter in Taiwan (China) (two specimens collected) and the Philippines (one record [several specimens] from Luzon). It has declined markedly since the 1970s.

Countries occurrence:
Japan; Philippines; Taiwan, Province of China
Continuing decline in area of occupancy (AOO): Yes
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 350
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 11-100
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The global population is estimated to number a few thousand based on an analysis by BirdLife International (2001). It is estimated to number 2,500-9,999 mature individuals, equating to 3,750-14,999 individuals in total, rounded here to 3,500-15,000 individuals. National population sizes have been estimated at c.50 individuals on migration and c.50 wintering individuals in Taiwan, and c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Japan.

Trend Justification:  A moderate and on-going population decline is suspected owing to habitat change within the breeding grounds, as well as the low number of recent records.
Current Population Trend: Decreasing
Additional data:
Number of mature individuals: 2500-9999 Continuing decline of mature individuals: Yes
Extreme fluctuations: No Population severely fragmented: No
No. of subpopulations: 1 Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: Yes
No. of individuals in largest subpopulation: 100

Habitat and Ecology [top]

Habitat and Ecology: It occurs mainly in the canopy of deciduous, mixed and evergreen subtropical forests, but also in tangled scrub, alder Alnus thickets and scrub around habitation. Migrants on the Osumi peninsula were seen in evergreen forest at 850-930 m (F. Crystal in litt. 2005). It arrives in the Izu Islands in late March or early April and leaves in late September and October.

Systems: Terrestrial
Continuing decline in area, extent and/or quality of habitat: Yes
Generation Length (years): 3.6
Movement patterns: Full Migrant

Threats [top]

Major Threat(s): It is threatened by habitat loss in the Izu Islands. On Miyake-jima, large areas of natural forest have been replaced with the fast-growing softwood Cryptomeria japonica for timber production. Road construction and developments for tourism are damaging its habitat on Miyake-jima and Mikura-jima. On Mikura-jima, there is a long-term plan to relocate a village, or build a new village at Nango, close to an important nesting area. However, the rate of habitat loss in its breeding range does not appear sufficient to account for its recent decline, suggesting that deforestation in its wintering grounds may also be an important threat. Another contributory factor to its decline may be the increased use of pesticides and other agrochemicals in its breeding range. The eruption in 2000 of Mt. Oyama destroyed or degraded 60% of the forest on Miyake Island, however, the population is thought to have recovered (Y. Odaya in litt. 2012). Further eruptions remain a major threat on Miyake, and there are also active volcanos in the Tokara islands, on the main breeding island of Kuchinoshima and the nearby Suwanosejima island, which currently holds the second biggest population in the chain (F. Crystal in litt. 2012). Trapping may also be a threat for migrants passing the Osumi Peninsula (F. Crystal in litt. 2005), but is not thought to be a major threat (Y. Odaya in litt. 2012).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
CMS Appendix II. It is legally protected in Japan. The entire Izu Archipelago has been designated as a national park and several important sites have been designated as Special Protected Areas. However, there are no rangers in the national park, and loss and modification of habitats continues on many islands. There is a small sanctuary on Miyake-jima.

Conservation Actions Proposed
Conduct surveys to clarify its winter distribution. Study the possible impact of pesticide use on the invertebrate prey of this and other species on the Izu Islands. Designate the Mariveles Mountains, Philippines, as a protected area. Maintain and enhance areas of suitable forest and woodland on the Izu Islands. Plan new development on these islands to minimise their negative effects on the habitats of this and other endemic species. Strengthen the human resources of the national park on the Izu Islands. Enforce legal protection in areas affected by trappers. Encourage surveys of potential wintering areas in Taiwan, the Philippines, Nansei Shoto Islands and intervening areas of suitable habitat.

Citation: BirdLife International. 2012. Phylloscopus ijimae. The IUCN Red List of Threatened Species 2012: e.T22715353A38197619. . Downloaded on 07 October 2015.
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