Historically, researchers focused on the role of sperm characteristics in fertilization success, but now female factors and cooperative processes are gaining recognition.

the male has a brighter red head and beak. ©User:JoJan / CC BY-SA 3.0 – Original / License In addition, some aviculturists (bird breeders) claim that female lovebirds tend to have rounder heads and ...

An illustration of a magnifying glass. An illustration of a magnifying glass.