More than one in 10 of all bird species are likely to have disappeared by 2100, scientists said on Tuesday.
The American researchers also said another 15% of birds would be very close to extinction by that time too.
If they do disappear, it could lead to more problems, as birds cut diseases by eating insects which carry them, and spread the seeds of plants and trees.
The falling numbers of birds has been blamed on climate change, and people destroying their habitat.
The researchers said birds which live on islands were most at threat, as well as birds that don't eat a wide range of foods.
If the birds disappear, it could also damage our crops.
Without birds to eat them, insects which eat the crops might grow out of control.