Lightest bird egg in proportion to body weight

The birds that produce the lightest eggs in proportion to their own body weight are the penguins. And of these, the proportionately lightest eggs of all are those laid by the largest modern-day species, the emperor penguin Aptenodytes forsteri of Antarctica. The egg of this species normally weighs 450 g, which is just 2.3% of the mother emperor penguin's body weight. Interestingly, the eggs produced by the world's smallest penguin species, the little blue or fairy penguin Eudyptula minor, native to southern Australia and New Zealand, are proportionately twice as heavy as those of the emperor penguin, because each egg weighs 52 g, which is 4.7% of the mother little blue penguin's body weight.