With brains proportionately larger than those of reptiles and amphibians bird generally display very complex behavior.Avian behavior is particularly intricate during breeding season. when bird engage in elaborate rituals of courtship.Because eggs are shelled when laid fertilization must be internal copulation involves contact between the mate vent the openings to their cloacas after egg are laid the avian embryo must be kept warm through brooding by the mother father or both depending on the species.