Our findings suggest that there is real potential for drug-related deforestation to negatively affect populations of migratory birds. Many of these species are unusually concentrated in winter in Central America, which has a comparatively smaller area than their summer breeding regions in North America.

For 1 in 5 migratory species that travel to Central American forests annually, including familiar birds like the Baltimore oriole, more than 50% of their global population winters in areas that are becoming more attractive to traffickers. For half of migratory species, at least 25% of their populations winter in these areas.

As examples, an estimated 90% of the endangered golden-cheeked warbler population spends winters in these vulnerable landscapes, along with 70% of Philadelphia vireos and 70% of golden-winged warblers.

Why it matters

Nearly half of Earth's migratory bird species are declining, and 1 in 5 species are at risk of extinction. Since 1970, North America alone has lost 3 billion breeding birds—more than 25% of its total population. Birds perform many important ecological roles, including eating insects, pollinating plants and dispersing seeds, and their presence often is a reliable measure of the overall health of an ecosystem.