The study looked at how birds and biodiversity change in tropical forests that grow back after being cut down. They found that while the total number of bird species is lower in these regrown forests compared to untouched ones, the number of specialist bird species increases over time. The variety of functions that birds perform in these forests stays similar between regrown and untouched areas, but young regrown forests have more diverse functions than older ones. This means that regrown tropical forests can help with important ecosystem functions, but older forests are better for overall bird diversity.