Data Zone
Justification of Red List category
This species is listed as Vulnerable due to a suspected rapid and continuing population decline caused by unsustainable levels of exploitation for the cagebird trade, following a rapid increase in the volume of trade and an increase in the price per bird.
Population justification
Quantitative population estimates do not exist for this species and, due to the presence of extensive trapping, a total population estimate cannot be calculated from population density estimates. However, the species is described as common on Java and Bali (Eaton et al. 2016). Weeklong ornithological surveys across 27 sites on nine mountains in West-Central Java between 2018 and 2020 for example found the species at 14 sites and on 7 mountains with a mean encounter rate of 0.39 groups/hour (range = 0.19 to 0.66 where present; C. Devenish, A. R. Junaid and S. Marsden in litt. 2020). During the ‘Big Month’ citizen science event (conducted in January 2020 comprising 22,054 checklists) across Java and Bali moreover, the species was recorded in 61 (0.77%) of the 7,935 tetrads (2 × 2 km squares) visited (T. Squires and S. Marsden in litt. 2020).
Trend justification
On the basis of the observed numbers in markets, it has been suggested that a '30% reduction in global population size over the past 10 years is a reasonable, if not conservative assumption' (Lim et al. 2019). As such, the species is assessed as having a decreasing population size. Judging the likely rate of population decline is difficult in this circumstance however. There are anecdotal reports of greatly reduced numbers at multiple sites across Java (including possibility of local extinction across Sukapua, Resmi Tinggal Village, Kertasari, and Bandung due to extensive trapping during 2009-2012; Akbar and van Balen 2020), where the species would be expected to be abundant (S. Mahood in litt. 2019; F. Rheindt in litt. 2019), coupled with inferred rising prices for the species in bird markets implying a reduction in availability and the strong impression that the numbers recorded in trade are far above a sustainable number (Lim et al. 2019). Symes et al. (2018) assigned probability curves according to expert opinion on trade desirability in conjunction with accessibility (based on a distance to forest edge from remote sensed forest data) to determine likely rates of population loss over the next three generation or ten year period: across the entire Sundaic range of the pre-split species, the estimated loss was 55%, but this analysis had no term to account for reproduction. While there is no direct data that can be used to estimate a rate of decline, it is suspected that a decline in excess of the threshold of 30% has been occurring over the past ten years, and this rate is not likely to diminish in the near future. There is a need for more field data that can be used to estimate the actual rate of decline, and for additional data to track numbers and prices at a sample of Javan markets.
Zosterops melanurus has two subspecies melanurus and buxtoni, which are both present in Indonesia. Z. m. melanurus occurs on Java and Bali, and Z. m. buxtoni is restricted to the western tip of Java (Lim et al. 2019; van Balen 2019). Populations of Z. (orientalis) 'buxtoni' in Sumatra are tentatively accepted as being a previously misidentified population of Z. auriventer tahanensis (Lim et al. 2019), but it is a priority to establish if this is in fact the case. On Java the species ought to be one of the commonest birds throughout low to mid-elevations with forest (including secondary), plantations and mature gardens (van Balen 1999). However the impact of very high trapping pressure appears to be that it is very scarce or absent from some suitable areas, and much reduced in abundance across most of the island (Lim et al. 2019). However, the species appears to have colonised Jakarta in recent decades (van Balen 2019), likely due to escaped cagebirds adapting to the novel environment. On Bali it may now be restricted to forested uplands and protected areas (eBird 2019).
Sangkar White-eye is predominately a forest species, occurring in deciduous, broadleaf evergreen/semi-evergreen and swamp forest, but it can also be found in forest edge, secondary growth, woodland, farmland, thickets, mangroves, scrub and wooded cultivation such as parks and mature gardens (van Balen 2019). The species is found from 100 m to 2,500 m (van Balen 1999), but the recent establishment in Jakarta (van Balen 2019) is near sea-level. Breeding takes place between January and October with a clutch size of two (van Balen 2019).
This is one of or the most numerous species observed for sale in bird markets on Java (Chng et al. 2015; Chng and Eaton 2016; Chng et al. 2016), and is suspected to be the most frequently trapped species from the wild in Java, and speculated to be the most heavily traded bird species of all (Lim et al. 2019). 2,339 individuals were counted in a three-day inventory of the main bird markets in Jakarta in 2014 (Chng et al. 2015), 526 were for sale in Sukahaji market, Bandung on 4th September 2016 and 3,538 individuals were counted across five markets in central and eastern Java between 22-24th June 2015 (Chng and Eaton 2016). These snapshots indicate that annually the total number caught and traded is exceptionally large, and there is some evidence that the volume of trade has been increasing in the past two decades. A clear increase in volume of trade occurred in the pre-split parent species, Oriental White-eye, on Sumatra, where the pattern of trade is considered to be driven to a large extent by demand on Java (Chng et al. 2018). A 2018 survey of bird ownership involving over 3,000 households in all six of Java’s provinces additionally estimated that 136,909 ± 70,163 individuals, and probably a large proportion of c. 1,557,931 ± 379,872 White-eye species are currently kept in Java alone (Marshall et al. 2020). Trade volume increased over 300% between 2004 and 2012-13 (Harris et al. 2015); while there doesn't appear to be equivalent data on Java itself, this increase is highly likely to have also occurred on Java at a similar time. The species may also be prone to habitat loss and degradation, with only 12,000 km2 of forest remaining and deemed suitable across Java alone (Akbar and van Balen 2020). However, due to its resilience towards some degree of habitat degradation, any detrimental effects are likely small.
Conservation Actions Underway
The species occurs throughout most national parks across Java (Akbar and van Balen 2020). Bird keepers have additionally bred the species in captivity, albeit a stable captive-breeding programme is yet to be established (Nijman et al. 2018).
Conservation Actions Proposed
Gain more information on the size of the population of this species and monitor the population decline. Research general ecological behaviours such as territoriality, dispersal, breeding times, and mortality (Akbar and van Balen 2020). Investigate the extent of trapping for the cage-bird trade and its impact on the population decline. Investigate how commercial captive breeding programmes could be implemented and regulated to supply the demand of the high consumption of trapped birds (Marshall et al. 2020).
10-11 cm. Bright yellow typical white-eye with a medium width bright white eye-ring, atypically occurring in two forms: all yellow or white bellied with a central yellow dividing stripe. Field identification from Swinhoe's, Hume's and Indian White-eyes on plumage and vocalisations still requires some clarification.
Text account compilers
Fernando, E., Elliott, N., Martin, R.
Contributors
Devenish, C., Junaid, A.R., Mahood, S., Marsden, S., Marshall, H., Rheindt, F. & Squires, T.
Recommended citation
BirdLife International (2024) Species factsheet: Sangkar White-eye Zosterops melanurus. Downloaded from
https://datazone.birdlife.org/species/factsheet/sangkar-white-eye-zosterops-melanurus on 22/11/2024.
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 22/11/2024.