Aclutch ofeggs is the group of eggs produced bybirds,amphibians, orreptiles, often at a single time, particularly those laid in anest.
In birds, destruction of a clutch bypredators (or removal by humans, for example theCalifornia condor breeding program) results indouble-clutching. The technique is used to double the production of a species' eggs, in the California condor case, specifically to increase population size.
Clutch size differs greatly betweenspecies, sometimes even within the samegenus. It may also differ within the samespecies due to many factors includinghabitat, health, nutrition, predation pressures, and time of year.[1]Clutch size variation can also reflect variation in optimal reproduction effort. In birds, clutch size can vary within a species due to various features (age and health of laying female, ability of male to supply food, and abundance of prey), while some species are determinant layers, laying a species-specific number of eggs. Long-lived species tend to have smaller clutch sizes than short-lived species (see alsor/K selection theory). The evolution of optimal clutch size is also driven by other factors, such asparent–offspring conflict.
In birds, ornithologistDavid Lack carried out much research into regulation of clutch size.[2] In species with altricial young, he proposed that optimal clutch size was determined by the number of young a parent could feed until fledgling. In precocial birds, Lack determined that clutch size was determined by the nutrients available to egg-laying females. An experimental study in brant geese (Branta bernicla), which rarely lay more than five eggs, found that the probability of an egg successfully leading to a fledged gosling declined from 0.81 for two-egg clutches to 0.50 for seven-egg clutches, whilst the nesting period increased with the increasing number of eggs laid. This suggests that there is no benefit for female brant geese to lay more than five eggs.[3]
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