BirdLife species factsheet for Javan Oriole
Javan Oriole (Oriolus cruentus) is endemic to the island of Java in Indonesia. It inhabits evergreen and moss forest as well as forest edge at elevations of 1,200-1,800 m (Walther et al. 2020). Javan Oriole is not well known and observational records are scarce. Since 1980, the species has only occasionally been observed in highland forest (Jihad in litt. 2016, B. van Balen in litt. 2016, J. Eaton in litt. 2018, eBird 2020). Potential threats to Javan Oriole include habitat loss and degradation (Walther et al. 2020); the species is not known to be traded in cagebird markets, which could be a sign of its apparent rarity in the wild (Jihad in litt. 2016, J. Eaton in litt. 2018).
The population size has not been quantified. Available evidence suggests that the species is very rare, but may potentially be overlooked (Jihad in litt. 2016, B. van Balen in litt. 2016, J. Eaton in litt. 2018). Tentatively, the population size is here placed in the band 250-999 mature individuals, though this may be revised as soon as new information is available.
Javan Oriole has been considered Least Concern (BirdLife International 2020). However, new information highlighting its potential rarity suggest that the species may warrant a change in Red List status. Therefore, we have fully reviewed the species here against all criteria.
Criterion A – The timeframe relevant for the assessment against Criterion A is ten years for this species (one generation length being 2.7 years; Bird et al. 2020)*, and any population changes therefore have to be quantified for the period between c. 2010 and 2020, or projected to 2030. There are concerns about the status of the species, but the population trend is difficult to quantify. Over the past few decades, evidence for its rarity has become apparent as the species has only been recorded a few times since 1980 (Jihad in litt. 2016, B. van Balen in litt. 2016, J. Eaton in litt. 2018, eBird 2020). It is however unclear whether the low number of records indicate a genuinely rare but stable population, or whether they are a sign of declines in the species.
Forest loss has however been low within the range, amounting to <2% over the past ten years (Tracewski et al. 2016, Global Forest Watch 2020). The species is not (or only very rarely) recorded in cagebird markets (Jihad in litt. 2016, J. Eaton in litt. 2018, Walther et al. 2020) and it is unknown whether trade causes additional population declines. As no further potential threats are currently known to the species, it is therefore likely that the population is stable at a low number or undergoing only slow declines. However, in order to fully assess Javan Oriole against Criterion A, we need information on the population trend. What is the likely rate of population change since 2010? Which threats is the species facing, and what are their potential impacts on the population size?
Criterion B – The species’s range is confined to the highlands of Java. The Extent of Occurrence (EOO) is 58,400 km2. The maximum Area of Occupancy (AOO), as calculated by a 4-km2 grid over the area of mapped range, is 28,148 km2, though this may be an overestimate given the apparent rarity of the species. Based on our current information, both EOO and AOO are too large to warrant listing as threatened under Criterion B; thus Javan Oriole is considered Least Concern under this criterion.
Criterion C – The population size has not been quantified. Available evidence suggests that the species is very rare, but may potentially be overlooked (Jihad in litt. 2016, B. van Balen in litt. 2016, J. Eaton in litt. 2018). Tentatively, the population size is here placed in the band 250-999 mature individuals, though this may be revised as soon as new information is available. The species would therefore meet the initial threshold for listing as Endangered under Criterion C, but to do so further conditions must be met.
We tentatively suspect that the species is undergoing a slow decline. A suspected decline, however, precludes a listing as threatened under Criterion C. The rate of decline is unknown, and thus the species cannot be assessed against subcriterion C1. We have no information on the subpopulation structure, but based on the distribution range it is conceivable that the species forms two disjunct subpopulations. Assuming that the true population size is closer to the lower end of the estimate of 250-999 mature individuals, no subpopulation would contain more than 250 mature individuals. Overall, despite the small population and subpopulation sizes, the level of data quality does not allow a listing as threatened; nevertheless, Javan Oriole qualifies as Near Threatened, approaching the threshold for listing as threatened under Criterion C2a(i). We therefore seek additional information regarding the population size and subpopulation structure of Javan Oriole.
Criterion D – The population size is tentatively placed in the band 250-999 mature individuals. Javan Oriole thus warrants listing as Vulnerable under Criterion D1.
The AOO is too large to meet or approach the threshold for listing as threatened; it therefore depends on the number of locations** of occurrence whether Javan Oriole additionally qualifies for listing as threatened under Criterion D2. Based on currently available information, the number of locations** cannot be determined. We therefore request recent information on threats to Javan Oriole and their potential impacts on the population size, in order to accurately quantify the number of locations** of occurrence.
Criterion E – To the best of our knowledge, there has been no quantitative analysis of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.
Hence, based on currently available information, it appears that the species warrants listing as Vulnerable under Criterion D1, but it is possible that it also qualifies for listing as threatened under additional criteria. Therefore, up-to-date information is urgently sought regarding the population size, structure and trend of Javan Oriole, as well as the intensity and impact of threats the species is facing.
Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status and the information requested. By submitting a comment, you confirm that you agree to the Comment Policy.
*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).
*The term ‘location’ refers to a distinct area in which a single threatening event can rapidly affect all individuals of the taxon present, with the size of the location depending on the area covered by the threatening event. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).
An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
Bird, J. P.; Martin, R.; Akçakaya, H. R.; Gilroy, J.; Burfield, I. J.; Garnett, S.; Symes, A.; Taylor, J.; Šekercioğlu, Ç.; Butchart, S. H. M. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.
BirdLife International. 2020. Species factsheet: Oriolus cruentus. http://www.birdlife.org (Accessed 26 May 2020).
eBird. 2020. eBird: An online database of bird distribution and abundance [web application]. eBird, Cornell Lab of Ornithology, Ithaca, NY, USA. http://www.ebird.org (Accessed 26 May 2020).
Global Forest Watch. 2020. World Resources Institute. http://www.globalforestwatch.org (Accessed 26 May 2020).
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. www.iucnredlist.org/technical-documents/categories-and-criteria.
Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.
Walther, B.; del Hoyo, J.; Collar, N.; Jones, P.; Kirwan, G. M.; Boesman, P. F. D. 2020. Black-and-crimson Oriole (Oriolus cruentus), version 1.0. In: Billerman, S. M.; Keeney, B. K.; ROdewald, P. G.; Schulenberg, T. S. (eds.). Birds of the World. Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bacori1.01 (Accessed 26 May 2020).