Egg embryo is adequately developed it hatches, i.e. breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering. The largest recorded egg is from a whale shark, and was in size. Whale shark eggs typically hatch within the mother. At and up to , the ostrich egg is the largest egg of any living bird, though the extinct elephant bird and some dinosaurs laid larger eggs. The bee hummingbird produces the smallest known bird egg, which weighs half of a gram (around 0.02 oz). Some eggs laid
Common kingfisher litter of fish remains and cast pellets. The common kingfisher typically lays two to ten glossy white eggs, which average in breadth, in length, and weigh about , of which 5% is shell. One or two eggs in most clutches fail to hatch because the parent cannot cover them. Both sexes incubate by day, but only the female at night. An incubating bird sits trance-like, facing the tunnel; it invariably casts a pellet, breaking it up with the bill. The eggs hatch in 19–20 days, and the altricial young are in the nest for a further 24–25 days, often more.