I've seen warblers feeding cowbirds that are twice their size. In addition, the birds tropical habitat is under siege. People in the tropics are cutting forests for timber and converting forests to grazing land. Coffee, once grown as a shade crop under a canopy of trees, is now grown in the bright sun. What used to be havens for birds are now being lost to open field coffee cultivation, Coggin says.
Pesticides also pose a threat to the species.
People in the tropics use agricultural chemicals that are banned in the United States. We visited a banana plantation in Costa Rica, and we saw bags of chemicals lying everywhere, Coggin says. To have a good crop and to have a cosmetically pleasing crop, they feel they must use lethal chemicals. Radio and cell-phone towers create another hazard for birds that migrate at night. They are attracted to lights, Coggin says.