part of developmental process involved in reproduction spermatid development cellular process involved in reproduction in multicellular organism sperm capacitation Avian spermatozoa do not require a period of capacitation, since they are competent to fertilize the egg without a prolonged sojourn in the oviduct or in a capacitation medium in vitro. Therefore, sperm capacitation can only be applied to Aves to refer to gene products involved in processes that occur prior to sperm being deposited from the avian male. The term cannot apply to processes occurring in the avian female reproductive tract. A process required for sperm to reach fertilization competence. Sperm undergo an incompletely understood series of morphological and molecular maturational processes, termed capacitation, involving, among other processes, protein tyrosine phosphorylation and increased intracellular calcium. sperm activation cell maturation