Birds build some staggering structures, from nests the size of walnuts to makeshift rafts and even apartment complexes.

European Bee Eater (Merops apiaster):

This bird digs a horizontal cavity into the sand on a river embankment. To build a nest, a bee eater hovers over a suitable site, drills a hole with its bill, alights and then excavates a burrow using its feet to scoop out sand. The bird chooses the nest site with the utmost care, as the soil has to be soft, yet safe from caving in.

Read about other utterly amazing bird nests over at BBC Earth.