Spectacled Flowerpecker (Dicaeum dayakorum) is a recently described species on the island of Borneo (Saucier et al., 2019). It has been observed in primary lowland forests, and is believed to be a mistletoe specialist. It is suspected to be absent from degraded forests, and sensitive to disturbance (Saucier et al., 2019). The population size is unknown.
The primary lowland forests of Borneo are threatened by logging, unsustainable agriculture, and land-use change (Wilcove et al., 2013). As a canopy specialist, it is assumed that these activities also present a threat to Spectacled Flowerpecker.
This previously undescribed species has not yet been assigned a Red List status. We have therefore reviewed the new information against all the criteria here.
Criterion A: The population trends for this species have never been assessed directly. It would appear to be a canopy specialist, and sometimes it is possible to estimate a species’s suspected population trend based on habitat loss across its range from deforestation and forest cover loss analyses. Other flowerpecker congeners on Borneo are believed to be in decline due to ongoing forest loss (see Black-sided Flowerpecker [BirdLife International, 2020]), and it is highly possible this overall trend is the same for the Spectacled Flowerpecker. Using an estimate of the rough range (based on the area that contains all the observation points, and assuming that that is its entire range), tree cover loss between 2000-2018 across this range was 13% (Global Forest Watch, 2020). To get a suspected rate of decline for this species, this rate must be extrapolated over the longer of three generations or 10 years. The generation length for Spectacled Flowerpecker has not been calculated, but based on the generation lengths of others in the Dicaeum genus, is estimated here to be between 2-3 years (Bird et al., 2020)*. As such, rates of decline for this species is calculated over 10 years. Hence, assuming that the population size for this species declines at the same rate as tree cover loss, this would equate to a rate of decline of 7% over 10 years, which would not reach the threatened threshold (≥ 30% decline over 10 years). If these assumptions are true, then Spectacled Flowercreeper could be considered Least Concern under this criterion.
However, this species is believed to be a mistletoe specialist, and while the species of mistletoe that this flowerpecker has been observed consuming are widespread throughout Borneo, the distribution of mature plants is patchy (Aukema, 2004). The distribution of this key resource is therefore believed to be scarce (Sourcier et al., 2019), and may be the determining factor regarding population decline rates when using habitat as a proxy. This factor is not considered in the above tree cover loss analysis, and as such, the rate of decline may be occurring undetected at a much higher rate.
Criterion B: Based on the six observation localities (Saucier et al. 2019), the Extent of Occurrence (EOO) for this species has been estimated to be 193,467 km². This is too big to trigger the threatened threshold (EOO < 20,000 km²) under this criterion. Spectacled Flowerpecker may be considered Least Concern under criterion B1.
Criterion C: The population size for this species has not been calculated. There is also not enough information on population densities or range size to provide a population size estimate. That this species has been scarcely observed in well-explored areas may indicate low population densities and a small population size. Equally, the bird is difficult to detect, and it may be that the core range (and therefore also the main population) has yet to be discovered (Sourcier et al., 2019). The lack of information here means there could be a large population experiencing gradual declines, or a small population experiencing rapid declines.
Criterion D: Again, the lack of population information means it is impossible to know whether this species meets the threshold for classification as threatened under this criterion. Additionally, the AOO cannot be calculated due to lack of knowledge about its distribution. Furthermore, the number of locations is dependent on knowledge about threats. Currently, the only potential threat known to Spectacled Flowerpecker, is habitat loss from deforestation. Here, a location is defined as a geographically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present (IUCN Standards and Petitions Committee, 2019). Estimating how many geographically distinct areas there are in relation to habitat loss, requires better information about this species’s range.
Criterion E: To the best of our knowledge, no quantitative analysis has been carried out for this species, so it cannot be assessed against criterion E.
Without more information, Spectacled Flowerpecker (Dicaeum dayakorum) may warrant listing as Data Deficient due to uncertainty around population size and rates of decline. We therefore seek the following information:
- What are the population trends, what rates are they occurring at, and what are the drivers of trends? What is the population size and subpopulation structure?
- How dependent are Spectacled Flowerpecker on mistletoe? What trends are occurring for the mistletoe? How much is mistletoe affected by deforestation or harvest?
- What is the distribution of this species? How widespread is suitable habitat? How threatened is Spectacled Flowerpecker by forest loss, particularly in relation to its mistletoe specialism?
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’s 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).
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.
Aukema, J. (2004) Distribution and dispersal of desert mistletoe is scale-dependent, hierarchically nested. Ecography, 27, 137–144.
Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S., Symes, A., Taylor, J., Şekercioğlu, Ç.H. and 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: Dicaeum monticolum. Downloaded from http://www.birdlife.org on 21/05/2020.
Global Forest Watch. 2020. World Resources Institute. http://www.globalforestwatch.org (Accessed 21 May 2020).
IUCN Standards and Petitions Committee. 2019. Guidelines for using the IUCN Red List Categoreis and Criteria. Version 14. http://www.iucnredlist.org/documents/RedListGuidelines.pdf
Saucier, J.R., Milensky, C.M., Caraballo-Oritz, M.A., Ragai, R., Faridah Dahlan, N., Edwards, D.P., 2019, A distinctive new species of flowerpecker (Passeriformes: Dicaeidae) from Borneo, Zootaxa 4686 (4), pp : 451-464.
Wilcove, D.S., Giam, X., Edwards, D.P., Fisher, B. & Koh, L.P. (2013) Navjot’s nightmare revisited: Logging, agriculture and biodiversity in Southeast Asia. Trends in Ecology and Evolution 28: 531‒540.