Has there been a 90% decline in the worldwide trade in birds?

Over the past few days a number of tweets have crossed my twitter feed that look more or less like this one:

This seems like great news for the trade in wild birds: a 90% decline in numbers in the worldwide trade since the EU ban on bird imports in 2005. However, we shouldn’t get too excited or complacent just yet, as this optimistic headline masks some important devil in the detail.

The study on which this headline is based, by Luis Reino and colleagues, is available here (though not necessarily freely):

http://advances.sciencemag.org/content/3/11/e1700783

Digging into the methods Reino et al. used, it is quickly apparent that two important caveats to the headline "90% decline" apply.

First, the analysis is based only on CITES-listed bird species in legal trade. Thus, it covers only around two-thirds of the species in legal trade – what the coverage is for the proportion of traded individual birds is unclear. It also does not address the illegal trade, and what proportion of the world’s bird trade is legal is necessarily also unclear.

Second, the analysis considers only species traded across biogeographic realms. Thus, species imported from Africa to Europe are covered by the analysis. Species traded within the Indo-Malay region are not. This matters, as in general even international trade often mainly concerns trade between geographically close countries.

To give one example, my PhD student Sushan studied the cage bird trade in Taiwan. In 2012, she visited a sample of shops across the country selling birds, identifying the species for sale, and counting (or estimating) the numbers of individual birds for sale. She found more than 25,000 individual birds for sale, from almost 250 species. More than 14,000 of the birds were from species from the biogeographic realm in which Taiwan sits. It is impossible to say how many of these birds came into Taiwan via the international trade in wild birds, as in theory some (or even all) could have been caught in country, or come from captive breeding facilities. However, from Sushan’s conversations with bird shop owners, it is likely that the international trade in wild birds was the source of a significant proportion of them.These birds would not have been included in Reino et al.'s analysis.

You can read more about Sushan’s work here:

http://discovery.ucl.ac.uk/1457036/

and here:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0127482

Obviously, the EU ban on bird imports is good news for the legal trade in CITES-listed bird species moved across biogeographic boundaries. What this means for the total worldwide trade in wild-caught birds is another matter. That said, international bans are likely to be one effective way to help decrease a trade that is often inhumane (many birds die in transit) and potentially highly damaging to wild bird populations. Other mechanisms will be needed to address the equally damaging trade that happens within national borders, such as that driving many bird population declines within Indonesia, as reported here:

http://www.traffic.org/home/2016/8/11/indonesias-bird-life-plundered-to-supply-javan-bird-markets.html