The red pigments in some fall leaves have proven to be a puzzle for researchers who debate why leaves bother to go red.

(Image credit: Charlie Riedel)

It's the peak of the fall migration season. This is when bird deaths from window collisions tend to spike, even though simple solutions can prevent this.

(Image credit: Angel Ruszkiewicz)

Millions of audio recordings of hundreds of bird species have revealed that artificial light is making the birds wake up earlier and go to bed later.

(Image credit: Rasit Aydogan)