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
Des Murs's wiretail to determine how wiretails find a mate. As is typical for south temperate insectivorous birds, during the breeding season of October to February Des Murs's wiretail lays a clutch of two to four eggs, but for the bird's mass these are about the largest eggs of any passerine bird. At long and wide, they weigh twice as much as expected for a 10 gram passerine and a clutch of four weighs more than the adult female - a feat equalled only by much more fecund kinglets. Little is known about incubation, fledging periods, or postfledging parental care due to the