An egg, a fertile egg and a developing chick

A hen does not need a rooster to lay an egg. Cooperative Extension's embryology teaching distinguishes egg production from fertilization: only a fertile egg has the potential to develop into a chick under appropriate incubation conditions. An egg's shell colour does not establish fertility.

The egg provides the materials needed for embryonic development. Breeder nutrition therefore matters before incubation begins. Temperature, humidity, ventilation and turning then influence development; supplying warmth alone is not a complete incubation system.

Fertilization, embryo survival and successful hatching are separate outcomes. An egg that does not hatch might be infertile or might contain an embryo that died. Distinguishing these possibilities requires observation and appropriate expertise rather than counting every failed egg as proof that the rooster is infertile.

The transition from egg to chick also requires preparation for the living animal. A successful hatch creates a need for suitable brooding, water, feed and safe handling. Children should wash their hands after handling birds or eggs and should not kiss chicks. The biological interest of a hatching project should be accompanied by plans for the chicks' continuing care and homes, rather than treating the hatch as the end of the activity.