Assessment of the historical population size of an endangered bird, the black-faced spoonbill (Platalea minor) by analysis of mitochondrial DNA diversity

We present a practical case of inferring historical demography in an endangered avian species, the black-faced spoonbill Platalea minor, which may be of reference for strategizing conservation planning for species lacking historical records. We applied a genetic approach, complemented by limited knowledge of demographic parameters and life history, to infer the historical population size in the blackfaced spoonbill, based on 2369 bp of three protein-coding mitochondrial DNA fragments from 87 individuals. The best estimate of θ (a product of two times the female effective population and the mutation rate) was 0.00028, which led a historical population size of 10 320 (95% CI: 1976-37 254) individuals - roughly nine times larger than the current estimated global population size of 1206 individuals. For an avian species lacking historical demographic records, this study extrapolates the occurrence of a severe and probably recent historical population reduction in the endangered black-faced spoonbill. We suggest that the population decline of this bird might not be fully explained by factors such as the Korean War or loss of habitat; rather, a bottleneck resulting from pollution by pesticides seems more congruent with the demographic history in terms of the scale of the population reduction and the timing and pattern of recovery. Environmental monitoring is therefore suggested as a proactive step to prevent future pollution or disease outbreak.