Migratory birds drop dead in US potentially in hundreds of thousands

Migratory birds are dropping dead in the US, potentially in the "hundreds of thousands", experts have said. Bluebirds, flycatchers, sparrows and warblers are among the species "falling out of the sky" as part of a mass die-off, said Martha Desmond, a professor at New Mexico State University. The wildfires may have contributed to the deaths of the birds, biologists said.