Egg incubation

In birds in contrast, the sex of offspring is genetically determined, but in many species a constant and particular temperature is necessary for successful incubation.

[3] The Namaqua sandgrouse of the deserts of southern Africa, needing to keep its eggs cool during the heat of the day, stands over them drooping its wings to shade them.

The humidity is also critical, because if the air is too dry the egg will lose too much water to the atmosphere, which can make hatching difficult or impossible.

[4] Experiments with great tits show that females compensate for the potential effects of differential heating by moving the eggs homogeneously within the clutch.

Possibly the most common pattern is that the female does all the incubation, as in the Atlantic canary and the Indian robin, or most of it, as is typical of falcons.

The incubation period, the time from the start of uninterrupted incubation to the emergence of the young, varies from 11 days (some small passerines and the black-billed and yellow-billed cuckoos) to 85 days (the wandering albatross and the brown kiwi).

It can be an energetically demanding process, with adult albatrosses losing as much as 83 g of body weight a day.

The freshly laid eggs of domestic fowl, ostrich, and several other species can be stored for about two weeks when maintained under 5 °C.

[10] Incubation periods for birds: The only living mammals that lay eggs are echidnas and platypuses.

Various species of sea turtles bury their eggs on beaches under a layer of sand that provides both protection from predators and a constant temperature for the nest.

[16] Brooding occurs in some invertebrates when the fertilised eggs are retained inside or on the surface of the parent, usually the mother.