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A recent international study co-led by The Chinese University of Hong Kong (CUHK) has tested a new way of monitoring the bird trade. The research team used an air sampler to collect tiny fragments of DNA, known as environmental DNA (eDNA), from the air within a Hong Kong bird market. Those eDNA sequences were enough to begin building an inventory of birds being sold in the market using a technique called DNA barcoding. The team hopes that this method can help with monitoring and enforcement efforts that lead to better conservation and management of birds traded globally. The findings have been published in the open access journal Environmental DNA.

Throughout Asia, hundreds of bird species are caught in the wild to be sold as food, as pets, for religious practices and for singing competitions – threatening native wildlife populations. As an importer and re-exporter of over 10,000 birds each year, Hong Kong has a unique opportunity to monitor the trade, but the volume of trade and the lack of expertise in identifying birds pose significant obstacles.

Professor Shelby McIlroy, corresponding author of the study and Assistant Professor in CUHK’s School of Life Sciences, said: “The reasons we monitor the wildlife trade are numerous. Firstly, trade data help to ensure that laws put in place to protect endangered species and restrict the trade in them are being followed. But even for species that are not yet threatened, it’s important that we track the trends within these markets, so that we can prevent these species from becoming threatened by the trade.”

With a background in using eDNA to examine biodiversity, Professor McIlroy teamed up with ornithologist Professor Caroline Dingle from Capilano University in Canada. Professor Dingle commented: “Currently the trade is monitored primarily through in-person market surveys and collation of data from various trade databases. The challenge with in-person surveys is that they are time-consuming and some species can be missed, because they are kept either in crowded cages or purposely out of view. These species are still shedding DNA in the market and can be detected through eDNA analysis, even when not visible to a surveyor.”

The team used a group of parrots living in a small enclosure to verify the method and confirm 100% detection accuracy of resident birds. They then headed to the Yuen Po Street Bird Garden, a 3,000 sqm market that is the main site for bird sales in Hong Kong. Compared to visual surveys on the same day, airborne eDNA techniques were effective at detecting abundant species but failed to detect some of the rarer species within such a large, open area.

“We are working on ways to improve the limits of detection in outdoor areas but this eDNA method could already be an excellent tool for the sampling of enclosed cargo containers where visual assessments are particularly difficult,” added Professor McIlroy. “The Hong Kong Customs has a huge job in monitoring the trade, with many noteworthy seizures of illegal wildlife in the past years. We hope that, as researchers, we can provide tools to make their job a little easier.”