Image copyright Getty Images Biologists in New Mexico have sounded the alarm after thousands of song birds were found dead in recent days.
New Mexico State University Professor Martha Desmond told local media that the reason for the mass die off is a mystery but could be tied to smoke from wildfires, or the recent cold weather.
The number of birds that have died may now be in the "millions", she said.
Scientists have reported North American bird populations have declined massively in recent years.
