The White-breasted Monarch (Symposiachrus menckei) is endemic to Mussau Island (400 km2) in the St Matthias group of Papua New Guinea, where it is considered common (Dutson 2011, Clement 2018). The species is currently listed as Near Threatened under Criterion C1. Based on a recent analysis of forest loss data from 2000-2012 (Tracewski et al. 2016), we are undertaking a review of the species’s Red List Category.
Our current information on the species’s conservation status will now be compared to all Red List Criteria.
Criterion A – We have no data on population trends. A recent analysis of forest loss data from 2000-2012 indicated that forest was lost within the species’s range at a rate equivalent to 3.5% across three generations (12.9 years; Tracewski et al. 2016). Assuming the population has declined at the same rate as the forest cover, the species is suspected to have undergone a reduction of 3% over the past three generation lengths, and assuming that forest loss continues at a similar rate, the population may be assumed to continue to decline at this rate in future. This does not approach the thresholds for listing the species as threatened under Criterion A. The species is therefore assessed as Least Concern under this criterion.
Criterion B – The species’s Extent of Occurrence (EOO) is estimated at 320 km2. This meets the threshold for Endangered under Criterion B1. The species’s Area of Occupancy (AOO) has not been quantified, but based on a 4 km2 grid placed over the area of mapped range, must be smaller than 344 km2, and therefore meets the threshold for Endangered under Criterion B2. However, to list the species as threatened on the Red List under Criterion B, two of conditions a-c must also be met.
The species is not severely fragmented. The main threat to the species is considered to be forest loss due to logging, which is estimated to be occurring at a rate of 3.5% across three generations (12.9 years; Tracewski et al. 2016). The number of locations is therefore likely to be significantly greater than 10. Therefore, condition a is not met. Based on the analysis of forest loss (Tracewski et al. 2016), there is an estimated continuing decline in the extent of habitat and the species’s population size and area of occupancy can also be inferred to be undergoing a continuing decline. Condition b is met. There is no evidence that the species’s population or range size are undergoing extreme fluctuations. Condition c is not met.
Although the species’s EOO and AOO both fall beneath the thresholds for listing the species as Endangered under Criterion B, only one of the three conditions is met. Therefore, the species is assessed as Least Concern under this criterion.
Criterion C – The species’s population size has not previously been estimated and no survey data are available, but it has been described as ‘common in forest and fairly common in secondary regrowth habitats (Dutson 2011). Based on the estimated area of forest with at least 50% canopy cover in the species’s mapped range in 2012 (168 km2), the recorded population densities of closely-related species with a similar ecology (Monarcha melanopsis: 20 individuals/km2 in Lowland rainforest in Papua New Guinea [Bell 1982]; Monarcha loricatus: 213 individuals/km2 in primary/secondary forest in Buru, Indonesia [Marsden et. al. 1997]), and assuming that 50% of suitable habitat is occupied, the species’s population size is estimated to fall within the range 1,680 – 17,892 individuals, which is roughly equivalent to 1,120 – 11,928 mature individuals. This could qualify the species for listing as Endangered, Vulnerable or Near Threatened under Criterion C, depending on where the true population size is most likely to fall. Given that the species is described as common, the actual population size may be more likely to fall at the higher end of this range. To list the species as threatened on the Red List under Criterion C further conditions must also be met.
A continuing decline in population size can be inferred from the analysis of forest loss (Tracewski et al. 2016). We do not have population data from which to estimate the rate of decline, so the species does note warrant listing as threatened under Criterion C1.
There is no evidence that the species has multiple subpopulations, so the species’s population is not composed of separate subpopulations of up to 1,000 mature individuals, meaning that the species would not meet condition 2a(i). However, the species does meet condition 2a(ii). There is no evidence that the species’s population size is undergoing extreme fluctuations so the species doesn’t meet condition b.
Based on the information stated above, the species could qualify for listing as Endangered, Vulnerable or Near Threatened under Criterion C2a(ii). The decision on which category to use depends on the best estimate of population size. Given that the species has a small area of occupancy, but is described as common, it may be most appropriate to assess the species as Vulnerable under Criterion C2a(ii).
Criterion D – Based on the population estimates described above, the species’s population size does not meet the threshold for Vulnerable under Criterion D. Taking the smaller end of the estimated range of 1,120 – 11,928 mature individuals, the species could qualify as Near Threatened under this criterion. However, given that the species has been described as common, it is likely that the true population size is significantly larger than this, so it would probably be more appropriate to assess the species as Least Concern under Criterion D1.
The species is threatened by deforestation, but does not have a restricted area of occupancy of number of locations such that deforestation could drive the species to Critically Endangered or Extinct within a very short time. The species does not therefore meet the criteria for listing as Vulnerable under Criterion D2 and may thus be assessed as Least Concern.
Criterion E – To the best of our knowledge no quantitative assessment of the probability of extinction has been conducted for White-breasted Monarch, and so it cannot be assessed against this criterion.
Based on the above assessment, it is proposed to list the White-breasted Monarch (Symposiachrus menckei) as Vulnerable under Criterion C2a(ii). However, should evidence arise that indicates that the population size is likely to fall below 2,500 mature individuals, the species may be listed as Endangered under Criterion C2a(ii). Conversely, should evidence arise that indicates that the population size is likely to be greater than 10,000 mature individuals, the species may be listed as Near Threatened or Least Concern. To allow us to achieve a clearer assessment of the species’s status, information is requested on the White-breasted Monarch’s likely population size and population density.
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 about the proposed listing.
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.
Bell, H.L. (1982) A bird community of lowland rainforest in New Guinea I. Composition and density of the avifauna. Emu 82: 24-41.
Clement, P. (2018) White-breasted Monarch (Symposiachrus menckei). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. Retrieved from https://www.hbw.com/node/59240 on 25 September 2018.
Dutson, G. (2011) Birds of Melanesia: Bismarcks, Solomons, Vanuatu and New Caledonia. Bloomsbury Publishing.
Eastwood, C. (1996) Kavieng, Djaul and Mussau Island, New Ireland: a trip report. Muruk 8(1): 28-32.
Marsden, S.J., Jones, M.J., Linsley, M.D., Mead, C. and Hounsome, M.V. (1997) The conservation status of the restricted-range lowland birds of Buru, Indonesia. Bird Conservation International 7: 213-233.
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.