Bird Egg ‒ Anatomy

Birds are one of few vertebrate groups where vivipary does not exist. Any bird life sees the light of day only after hatching from an egg. Bird eggs vary in a size, colour and shape, but their interior construction is single.

Despite cavity nesters have spheric eggs, rock nesters (guillemots) have more conic shape (they can´t fall down from the rocks). Cavity nesters usually lie clearly white eggs (white colour is of low energetic costs and it is unnecessary to create mask colours in the darkness of the cavities). On the other hand, mostly birds which left their eggs in the nest unattended lie masked eggs.

Ostrich has the biggest eggs, but the biggest ratio egg: body mass is found in kivis (they usually lie two eggs only in the interval of weeks). Despite ostrich egg creates only 2% of its body mass, in the smallest eggs of hummingbirds it can be up to 25%.