Quick Take The official 4-species status was achieved only after reviewing recent genetic, morphological, and biogeographic ...

Imagine looking up at a sky so full of birds, they block out light from the sun. Passenger pigeons (Ectopistes migratorius) used to fly in flocks of hundreds of millions, maybe even billions, of birds ...

When species interact with each other, they do not evolve separately, but do so together. This process is called coevolution. Natural selection favors predators that are better at capturing prey, and ...