NT
Taiwan Green-pigeon Treron formosae



Taxonomy

Taxonomic note

Treron formosae and T. permagnus (del Hoyo and Collar 2014) were previously lumped as T. formosae following Sibley and Monroe (1990, 1993).

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.

IUCN Red List criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - -

Red List history
Year Category Criteria
2023 Near Threatened C2a(i); D1
2016 Near Threatened C1
2014 Near Threatened C1
Species attributes

Migratory status not a migrant Forest dependency medium
Land-mass type Average mass -
Range

Estimate Data quality
Extent of Occurrence (breeding/resident) 22,000 km2 medium
Extent of Occurrence (non-breeding) 101,000 km2 medium
Area of Occupancy (breeding/resident) 1,300 km2
Severely fragmented? no -
Population
Estimate Data quality Derivation Year of estimate
Population size 1250-2000 mature individuals poor estimated 2022
Population trend decreasing poor suspected -
Generation length 4.6 years - - -
Number of subpopulations 2 - - -
Percentage of mature individuals in largest subpopulation 1-89% - - -

Population justification: The global population of this species has not reliably been estimated. In Taiwan (China) it is believed to breed on only two small islands: Green Island and Orchid Island, with birds disappearing from the mainland during the breeding season (but a few birds apparently remaining on Taiwan year-round: eBird 2023). While the area of these two islands is small (15 and 47 km2 respectively) the species is described as not uncommon (Rueng-Shing Lin and Cheng-Ching Chiu in litt. 2023); nonetheless, Lin et al. (2016) reconciled that the total population size was still likely to be fewer than 1,000 mature individuals. On the Batanes islands (Philippines), the population size has not been estimated but applying equivalent densities as those observed on Taiwan, the population may number between 250-1,000 mature individuals. Overall therefore, the population is estimated as 1,250-2,000 mature individuals. This estimate is also congruent with the values of Brazil (2009), who suspected the population numbered between 200-2,000 mature individuals.

Trend justification: Formerly considered to be declining quite rapidly owing to habitat loss and hunting. However, forest loss in this species' range is now minimal: <1% in the three generations (13.8 years; Bird et al. 2020) to 2021 (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein). Hunting is a minimal threat in Taiwan but a greater one on the Babuyan and Batanes islands (Allen et al. 2006) and may be driving slow population declines. Consequently, the global population of this species is precautionarily suspected to be declining. The rate has not been quantified but is likely to be slow.


Country/territory distribution
Country/Territory Presence Origin Resident Breeding visitor Non-breeding visitor Passage migrant
Philippines extant native yes
Taiwan, China extant native yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Philippines Batanes Islands
Taiwan, China Lanyu

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Artificial/Terrestrial Rural Gardens suitable breeding
Artificial/Terrestrial Rural Gardens suitable non-breeding
Forest Subtropical/Tropical Moist Lowland major breeding
Forest Subtropical/Tropical Moist Lowland major non-breeding
Forest Subtropical/Tropical Moist Montane major non-breeding
Altitude 0 - 2000 m Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Biological resource use Hunting & trapping terrestrial animals - Intentional use (species is the target) Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Stresses
Species mortality
Biological resource use Logging & wood harvesting - Unintentional effects: (large scale) [harvest] Timing Scope Severity Impact
Past, Unlikely to Return Minority (<50%) Slow, Significant Declines Past Impact
Stresses
Ecosystem degradation, Ecosystem conversion
Biological resource use Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest] Timing Scope Severity Impact
Past, Unlikely to Return Majority (50-90%) Slow, Significant Declines Past Impact
Stresses
Ecosystem degradation

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Food - human - - non-trivial recent

Recommended citation
BirdLife International (2024) Species factsheet: Treron formosae. Downloaded from https://datazone.birdlife.org/species/factsheet/taiwan-green-pigeon-treron-formosae on 20/02/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org on 20/02/2024.