Data Zone
Justification of Red List category
This species has a very small range, split into three separate subpopulations. This species is considered to be declining as a result of habitat loss, and may also be being threatened by invasive species. Therefore, the species is precautionarily listed as Endangered, though further information regarding the impact of threats on the species may mean this warrants revising in the future.
Population justification
The population has been estimated at 4,425-5,286 individuals (Fujita et al. 2011), which is considered equivalent to 2,900-3,600 mature individuals. Estimates for the three islands were 1.953-2,285 individuals on Miyake-jima, 1,077-1,453 individuals on Mikura-jima and 1,394-1,548 individuals on Hachijo-jima (Fujita et al. 2011), equivalent to 1,300-1,550, 700-1,000 and 900-1050 mature individuals respectively.
Trend justification
Deforestation rates from Ł. Tracewski (unpublished data following Tracewski et al. [2016]) suggest that the species has lost c.10.9% of suitable habitat over the past 3 generations (c.12.5 years), which is believed to be causing a population decline.
Sittiparus owstoni is found on the three southern Izu Islands, Japan, namely Miyake, Mikura and Hachijo. Ł. Tracewski (unpublished data following Tracewski et al. 2016) estimated the maximum Area of Occupancy (calculated as the remaining tree area within the species’s range) to be c.33 km2.
Occurs in forested habitats, large gardens and urban parks (Gosler and Clement 2016).
The species shares a range with Izu Thrush Turdus celaenops (BirdLife Species Factsheet) and Izu Leaf-warbler Phylloscopus ijimae (BirdLife Species Factsheet). For these species an ongoing population decline is suspected; for Izu Thrush the impact of introduced predators is thought to have caused an observed rapid decline and for Izu Leaf-warbler habitat loss and fragmentation are considered to be causing a moderate decline. Siberian Weasel was introduced to Miyake-jima in the 1970s and domestic cats are also widely present, additionally enhanced populations of Large-billed Crow as a result of the availability of food via poor human rubbish disposal. Large areas of natural forest have been replaced by Cryptomeria for timber. Road-building and the creation of tourist infrastructure have also been noted to have reduced the extent of natural habitat. In addition the impact of volcanic eruptions is a potential threat to populations in that these events can degrade large areas of habitat. The eruption in 2000 of Mt. Oyama is estimated to have degraded 60% of forest on Miyake-jima, however populations of birds reportedly recovered relatively quickly from this event. There does not appear to be any evidence of impacts from introduced predators on the taxon, although Sittiparus varius nameyei was noted to have very poor breeding success due to brood predation by snakes, but this appears specific to the island of Kozushima and is not seen in S. owstoni on Miyake-jima (Yamaguchi and Higuchi 2005).
Conservation Actions Underway
The entire Izu Archipelago has been designated as a national park and several important sites as Special Protected Areas. There is a small sanctuary on Miyake-jima.
Conservation Actions Proposed
Research its ecology, especially the migratory movements of the Tokara Islands population. Maintain and enhance areas of suitable forest and woodland on the Izu Islands. Plan new development on the Izu Islands to minimise their negative effects on the habitats of this and other endemic species. Strengthen the infrastructure and human resources of the national park on the Izu Islands to improve enforcement of habitat conservation measures. Control predators, particularly Siberian weasel and Large-billed Crow. Instigate new controls on the dumping of garbage to reduce the numbers of Large-billed Crow.
Text account compilers
Westrip, J., Ekstrom, J., Khwaja, N., Butchart, S., Martin, R, Symes, A.
Contributors
Tracewski, Ł.
Recommended citation
BirdLife International (2024) Species factsheet: Izu Tit Sittiparus owstoni. Downloaded from
https://datazone.birdlife.org/species/factsheet/izu-tit-sittiparus-owstoni on 26/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 26/11/2024.