Turdus: Not the name of a vehicle for traversing time and space ( disguised as a public toilet) after all

Bird of paradise are known never to alight on the ground or a tree branch, as deduced from their absence of legs. It follows by the same token that in lieu of using nests they must lay hollow eggs that hover in mid-air; so naturally these eggs are sky-coloured as camouflage against egg-predating threats such as crows and naturalists.

Levitating eggs, caught by naturalist

Seen against the brown interior of a nest, however, blue eggs are not so well concealed, often causing naturalists to exclaim "My God, it's full of sky!" as their final communication to Mission Control just before they disappear part-way though an epic 5-year egg-collecting mission. I note in passing that this would make a great Stanley Kubrick / Peter Greenaway collaboration.

Moreno and Osorno note that the blue pigment is a drain on the female's metabolism, and have a theory that it is secreted as a signal to the male as to the resources invested in an egg -- giving him an incentive to hang around and take turns with brooding while waiting for the eggs to hatch.

However, on empirical grounds, Phillip Cassey does not rate for this theory. This is a pity because it would also explain why human mothers-to-be emphasise the bulge of their bellies with a coating of blue woad and sometimes some subtle gold adornment of the navel. YMMV.

This bird encourages its mate to take a greater share of the egg-brooding by involving him in the decoration of the nest. They spend many hours reading issues of Home & Garden together.