The age, that is, the duration of the life of a female bird at the point in time when her initial egg is laid; the earliest or youngest age at which a specific individual has produced an egg.
number of blastocysts implanted per litter
number of fetuses with external malformations to total number of live fetuses ratio +
number of fetuses with skeletal malformations to total number of fetuses ratio +
number of fetuses with visceral malformations to total number of fetuses ratio +