Collared Crow (BirdLife Species factsheet) is currently listed as Near Threatened, on the basis that it is suspected to be undergoing a moderately rapid population reduction that may approach the thresholds for listing as Vulnerable (30-49% decline over a three generation period, which is 21.9 years for this species). The global population size was considered likely to exceed 10,000 mature individuals based on an extrapolation from a high density observed in Hong Kong, hence placed in a band of 10,000 – 19,999 mature individuals. However, it has become evident that it is highly localised throughout the very large range, and this extrapolation from the density encountered in Hong Kong was inappropriate (P. Leader in litt. 2016, Leader et al. 2016).
Recent efforts to improve the accuracy of the global population estimate have been conducted through a combination of an exhaustive compilation of historical and recent records and targeted field surveys at different locations within the range (Leader et al. 2016). This has resulted in a far lower estimate of the total population size of around 2,000 individuals (Leader et al. 2016). No attempt was made to account for the potential presence of additional, unsampled locations holding numbers of the species during the assessment, and there are reports of this species at locations not included in the Leader et al. (2016) population estimate (S. Chan in litt. 2017). Therefore, this estimate should be taken as the lower bound of a population estimate rather than a mid-point.
The exercise did unearth a significant concentration of the species in eastern central China. Centred on the Dabie Shan mountain range in Henan, Hubei and Anhui provinces, an estimated 400-500 individuals were observed in the area over the course of a week in December 2014 (Leader et al. 2016). This indicates that additional localities with notable numbers may well be found. However, the presented estimate does represent a careful assessment of observations of the species, and it is unlikely that additional localities would increase the estimate by a large margin. Therefore, with careful consideration of the estimates presented for the multiple locations holding the species in Leader et al. (2016), the population is placed here in the band of 2,500 – 9,999 mature individuals.
The population structure does still require some clarification, though. While the centres of population are discrete and often distant from each other, reports of individuals or small groups between these may indicate a low level of continuing connection between locations, and with the apparent extirpation of the mainland Chinese Taiwan population (where there have been only three records in recent decades, with the most recent in 1987 [Leader et al. 2016]) no localities are divided by significant geographical barriers. Coupled with the apparent homology of the phenotype throughout the range, it could therefore be assumed that the species is made up of only a single subpopulation.
In light of the above, it is proposed that Collared Crow C. pectoralis meets the thresholds for listing as Vulnerable under Criterion C2a(ii), though we welcome any comments on the above points.
Leader P. J.; Stanton, D. J.; Lewthwaite, R. W.; Martinez, J. 2016. A review of the distribution and population size of Collared Crow Corvus torquatus. Forktail 32: 41-53.