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.
With climate change, there may be longer dry seasons.
"You can’t study the effect of changing environmental conditions and its relationship to bird populations without a long-term study and long-term data," Brawn says.
Brawn’s team looked at the relationship between population growth rates and the length of the dry season during those 33 years, then simulated another 50 years with an average of a 10 percent change in the rainfall pattern in Panama’s dry season.
The simulation suggests that, in time, the bird community will be very different under dryer conditions.
Seasonality in Panama is rain/no rain, says Brawn.
"We worked in a good forest — that is, relatively intact.
The study shows that even in a protected park, the large, global effect of climate change could make a lot of habitat unsuitable for a lot of species.
Brawn had a post-doctorate position with Karr at STRI.
Decades later, tropical forest ecologists began reporting that some tree species are sensitive to more intense seasonal drought.