Birds breed through a process called oviparity, where they lay eggs. Mating rituals vary by species. After mating, females lay eggs, usually in nests built by one or both parents. Eggs need incubation, which is often done by parents using body heat. Once hatched, chicks may be altricial (dependent on parents) or precocial (more independent). Parental involvement in chick-rearing varies widely among species.