Time hens continue to produce fertile eggs

If the rooster in a flock dies, or is removed, the hens will continue to produce fertile eggs for up to four weeks, depending on bird species. This is because there are "sperm nest" areas located in the oviduct of hens that collect and store semen for later fertilization of eggs. This is a natural survival mechanism for the production of a series of fertile hatching eggs even after the male is not available.

The period of time that fertile eggs can be produced without additional matings can extend to several weeks. If a rooster is removed from the flock and replaced by another, it may require 3 weeks before it can be assured that all eggs will produce chicks sired by the new rooster. The proportion of chicks sired by the new rooster will increase during this period, but some chicks sired by the old rooster may hatch. Birds like turkeys and waterfowl have longer periods during which fertile eggs can be produced without matings.