ZZ/ZW mechanism:
In this system, males have two identical sex chromosomes (ZZ) while females have two different sex chromosomes (ZW).
Female heterogametic:
Unlike the more common XY system in humans where males are the heterogametic sex, in ZZ/ZW systems, females are the heterogametic sex.
Some reptiles and insects also use this system:
Besides birds, a few reptiles and insects also exhibit the ZZ/ZW sex determination mechanism.
