Brood reduction

Brood reduction was originally described by David Lack in his brood-reduction hypothesis to explain the existence of hatching asynchrony in many bird species.

[3] If resources are limited, it benefits the parents to allow brood reduction, because it reduces the amount of work they must do and increases their chances of surviving and reproducing again in future years.

Facultative brood reduction depends on the conditions of that particular year, and only occurs when there is a limit to the resources available for the nestlings.

[7] This can be seen in several species of birds of prey, such as eagles, and depends on the size difference between the siblings and therefore the amount of time that passes between each egg hatching.

[7] In the crowned eagle, the time interval between eggs hatching is 3 days, and in this species the brood reduction observed is obligate.

Brood parasites lay their eggs in the nest of another bird species, relying on the host parents to raise their offspring.

[12] The brood-reduction hypothesis was first proposed by David Lack in 1947 to explain the evolution of hatching asynchrony and dominance hierarchy in the broods of some bird species.

[2] During these years, the asynchronous pattern allows the brood size to be reduced to an amount that can be supported by the parents, by either directly killing the weakest nestlings or by siblings out-competing them.