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
Yellow-chinned spinetail The tubular entrance tunnel rises almost vertically from the base to the top of the nest. The normal clutch is three, sometimes four, greenish white eggs. This spinetail is parasitised by the striped cuckoo ("Tapera naevia"), which lays one or two eggs in the nest, but it is not known how the cuckoo enters the nest or whether it or its offspring eject the host's young. This widely ranging bird is not considered threatened by the IUCN. Yellow-chinned spinetail The yellow-chinned spinetail ("Certhiaxis cinnamomeus") is a passerine bird found in the tropical New World from Trinidad and Colombia south to