Using market data and expert opinion to identify overexploited species in the wild bird trade

The wildlife trade involves thousands of vertebrate species and now rivals habitat loss as an extinction driver in some regions. However, its impacts are poorly known because field monitoring of wild populations is expensive, localized, and requires specialized expertise. We examined whether market data and expert opinion could be used to identify bird species that may be at risk from the trade in Indonesia. We asked expert ornithologists to characterize population trends of 38 species of Indonesian birds, including many heavily traded species. They identified 14 species as having undergone population declines, all of which are regularly traded, and only two of which are restricted to old-growth forests. Conversely, none of the untraded species was classified as declining. We combined the expert-derived population trends with data on changes in price and trade volume from Indonesian wildlife markets to see if market data could identify declining species. We found that severely declining species have a significantly different price-volume signal than stable/increasing species; the former are characterized by increasing market prices and declining volumes. Market data are much cheaper to collect than field data, roughly 1/30th the cost of a representative field study. We recommend a two-step approach to assess trade impacts on wild birds in Southeast Asia: coordinated market monitoring followed by field studies of species whose market signals indicate declining populations. Our findings, however, require further validation with higher resolution wild population and market data.