Black drongos introduced for pest control later threatened Guam’s native birds

A juvenile and an adult Black Drongo perch on a tree branch (ANI Photo) In 1935, the Japanese South Seas Development Company made a decision that would have repercussions for Mariana Islands' ecosystems for nearly 100 years. In search of a natural method for controlling agricultural pests, they imported black drongos (Dicrurus macrocercus) from Taiwan to Rota. At the time, it seemed a simple fix: introduce an insect-eating bird to protect crops. But nature rarely travels in straight lines.An experiment in pest control that would, decades later, become a cautionary tale of the unforeseen consequences of introducing species to new environments.A good-intentioned introductionThe black drongo is a striking bird, shiny black with a distinctive forked tail, native to South and Southeast Asia. An agile insectivore, it is known for its ability to catch insects on the wing and its bold, territorial nature. In 1935 these traits made it an attractive candidate for biological pest control on Rota, the third largest human-inhabited island in the Mariana archipelago. The drongos thrived in their new home.They adapted quickly to the island’s open habitats and lower elevations, where they found ab...