In the time that records have been kept of bird populations, 20 percent of all species have gone extinct. (discovermagazine.com)
The key result of the study is that with longer dry seasons and more intense seasonal drought, there is an overall negative effect on bird populations. (sciencedaily.com)
They then tracked bird populations in each experimental and control plot using point - count surveys, in which researchers look and listen for birds for a set amount of time. (sciencedaily.com)