Data Zone
Justification of Red List category
This species—described to science as recently as 2022—is endemic to the tiny island of Wangi-wangi, Indonesia, where it has a small population (500-1,000 mature individuals), Extent of Occurrence (EOO) and Area of Occupancy (AOO). Trapping for the songbird trade appears to have made it scarcer since its initial discovery, and it is therefore believed to have a limited number of Locations and be undergoing a continuing decline in mature individuals. Moreover, habitat loss caused by timber extraction and the expansion of tourism infrastructure is removing suitable habitat. With evidence from elsewhere in Indonesia that trapping for the songbird trade can cause rapid declines in Zosterops species, this species' small range and population size render it especially vulnerable to extirpation in the wild. Accordingly, it is listed a Endangered.
Population justification
Descriptively, this species is described as locally common (O'Connell et al. 2020, Eaton et al. 2021), but in eBird checklists generated (eBird 2023), it is evidently rarer than Z. flavissimus, with almost no search effort finding more then five individuals (where counts of 20+ Z. flavissimus are not uncommon). Based on 16 transects across the island, a density of 0.2 birds/hectare, or 20 birds/km2, was recorded in 2012/13 (unpublished data: D. O'Connell, S. Kelly and Adi Karya pers. comm.). The area of suitable habitat across Wangi-wangi is c. 60-80 km2, suggesting that the island may host up to c. 1,600 birds. However, there are numerous assumptions being made in this estimate which require consideration. First, all transects used to derive it were placed in secondary-type habitat, with qualitative reports (O'Connell et al. 2020, Menner 2023) that the species occurs at higher densities in the island's taller forests; because the area of taller forest is relatively small (c. 10 km2), it is suspected that even if birds here occur at a much higher density, the total population is unlikely to exceed 2,500 birds. Second, not all of the birds encountered will have been mature individuals. Third, data were collated 10 years ago, with evidence that the species may have been subject to trapping pressure and reduced in number since (see Population Trend). In the absence of data from which to derive robust minimum and maximum population bounds, it should be noted that the limits used here are somewhat arbitrary, albeit with relatively high confidence that they encapsulate all plausible scenarios. The total number of birds is estimated to number 800-2,500 birds, or 500-2,500 mature individuals, with a best estimate of 500-1,500 mature individuals.
Trend justification
The population is inferred to be declining because of two key threats: (1) habitat loss and degradation; and (2) trapping for the songbird trade.
Over the past ten years (2012-2022), remote sensing data indicate that approximately 5% of forest cover on Wangi-wangi has been lost (Global Forest Watch 2023, based on data from Hansen et al. [2013] and methods disclosed therein). This is thought to have some impact on the population size of this species, especially given many losses have been recorded in areas of more mature forest, where where this species is reportedly commonest (O' Connell et al. 2020; Menner 2021, 2023). However, there is also evidence that it persists in degraded habitats (O'Connell et al. 2020, eBird 2023, unpublished data: D. O'Connell, S. Kelly and Adi Karya pers. comm.) such that not all forest loss may directly impact the population size, although Menner (2023) regarded it 'dependent' on taller vegetation and 'sensitive to human habitat alteration'. Consequently habitat loss and degradation is suspected of causing some slow declines, with most impacts of this threat having been historical.
The second, perhaps most serious, threat to this species (trapping) is considerably harder to quantify, especially in the absence of repeated survey effort. The species has already been recorded in the songbird trade (O' Connell et al. 2020, Asian Songbird Trade Specialist Group in litt. 2023) but the impact this is having on wild populations is currently improperly known. However, observations in O'Connell et al. (2020), from a decade ago, that it was readily found and mist-netted in degraded habitats were not repeated by Menner (2021), who found it only, after several days of effort (albeit not at typically an optimal time of day), in mature habitat. More recently, Menner (2023) continued to find it distributed 'throughout the island'. Acknowledging that trappers are capable of such pressure (as demonstrated elsewhere in Indonesia), and the anecdotal reports that the species has indeed declined over the past decade, it is accepted that the species is undergoing a continuing decline, although in the absence of repeated surveys, the rate of this decline is not currently estimated. Elucidating this should be considered an utmost research priority.
It is confined to the island of Wangi-wangi off south-east Sulawesi, Indonesia. It is, perhaps surprisingly, apparently absent from Wangi-wangi's close satellites of Oroho and Kapota (see O'Connell et al. 2020, Menner 2021).
It is confined to taller forest on Wangi-wangi than is Z. flavissimus, including agricultural areas where taller trees persist (Eaton et al. 2021). O'Connell et al. (2020) report it to be associated with 'thick tangles, epiphytes and vines on emergent large trees'.
The two critical threats to this species are habitat loss and degradation, and trapping for the Indonesian songbird trade. The former has been more extensive historically but continues at a slow rate, mostly as a result of localised timber extraction and the conversion of forest for tourism infrastructure. Trapping for the Indonesian songbird trade is plausibly the main threat to this species currently, with birds appearing in markets almost immediately after public attention to its existence was drawn. The scale of the trade is not currently well understood, nor is its impact on wild populations. However, the species is believed to be declining and given its small population size, and the history of Indonesian songbird trappers extirpating small-island taxa very quickly (Eaton et al. 2015, Collar and Wirth 2022), it is possible that this threat is, or becomes, very acute. The trade in this species is probably solely domestic, with most birds likely going to Java.
Conservation Actions Underway
The entire range is circumscribed by the Wakatobi National Park (UNEP-WCMC and IUCN 2023), although with ongoing trapping and forest cover loss, the level of protection this has so far conferred is unclear. More recently, an agreement between Prigen Conservation Breeding Ark (PCBA) (and KASI/Taman Safari) and Wakatobi National Park aims to strengthen protection for remnant habitat for Z. paruhbesar and (on other islands), the endemic taxon of Cacatua sulphurea paulandrewi (Menner 2021). This work has continued and in late 2023, PCBA were conducting the first comprehensive survey on the distribution, population status and ecology of the species (Menner 2023). Because of its recent formal description (Irham et al. 2023), Z. paruhbesar is not currently protected under any national or international legislation, although it is listed on 'Tier 1' (in immediate need of conservation action) by the Asian Songbird Trade Specialist Group (Collar and Wirth 2022). Following concern that trapping posed an imminent risk to this species, an insurance captive breeding population was established at PBCA where, as of August 2023, 23 birds were held (J. Menner in litt. 2023).
Conservation Actions Proposed
Continue to monitor habitat trends using remote sensing data. Investigate the feasibility of implementing reforestation programmes on Wangi-wangi to increase the area of suitable habitat. Continue captive breeding programmes (potentially at more than one facility) as an insurance against extirpation in the wild. Have the species protected under domestic Indonesian law and consider listing in CITES Appendices as a means to control and monitor trade in this species, which is likely the greatest future threat (although this threat is mostly for the domestic trade, such that it's unclear whether CITES listings will confer any meaningful protection).
Text account compilers
Berryman, A.
Contributors
Menner, J. & O'Connell, D.
Recommended citation
BirdLife International (2025) Species factsheet: Wangi-Wangi White-eye Zosterops paruhbesar. Downloaded from
https://datazone.birdlife.org/species/factsheet/wangi-wangi-white-eye-zosterops-paruhbesar on 05/01/2025.
Recommended citation for factsheets for more than one species: BirdLife International (2025) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 05/01/2025.