Ulovlig handel er svær at måle, men det er blevet anslået, at der er tale om enorme antal fredede fugle, der fanges, og argumentet, at et totalt forbud mod import af vilde fugle ville drive handelen under jorden og forårsage en stigning i ulovligt importerede fugle, er blevet hyppigt anvendt af modstanderne af et handelsforbud.
Illegal trade is difficult to measure, but it has been estimated that huge numbers of protected wild-caught birds are involved, and the argument that a total ban on the import of wild birds would drive the trade underground and cause an increase in illegally imported birds has been widely used by those who oppose a trade ban.