A clutch of
eggs is the group of eggs produced by
birds,
amphibians
Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
, or
reptiles, often at a single time, particularly those laid in a
nest
A nest is a structure built for certain animals to hold Egg (biology), eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of ...
.
In birds, destruction of a clutch by
predators (or removal by humans, for example the
California condor breeding program) results in ''double-clutching''. The technique is used to double the production of a species' eggs, in the California condor case, specifically to increase population size.
Size
Clutch size differs greatly between
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, sometimes even within the same
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
. It may also differ within the same
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
due to many factors including
habitat
In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
, health, nutrition, predation pressures, and time of year.
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 also
selection theory). The evolution of optimal clutch size is also driven by other factors, such as
parent–offspring conflict.
In birds, ornithologist
David Lack carried out much research into regulation of clutch size. 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.
Gallery
Image:Anas platyrhynchos (nest).JPG, Mallard (''Anas platyrhynchos''), very large clutch or possibly from two females
Image:Larus marinus eggs.jpg, Great black-backed gull
The great black-backed gull (''Larus marinus'') is the largest member of the gull family. It is a very aggressive hunter, pirate, and scavenger which breeds on the coasts and islands of the North Atlantic in northern Europe and northeastern Nort ...
(''Larus marinus''), small clutch
Image:Masked Lapwing Eggs.jpg, Masked lapwing (''Vanellus miles''), typical clutch
Image:Waterhoennest.JPG, Common moorhen (''Gallinula chloropus''), small clutch
Image:Aquila pomarina nest with eggs.jpg, Lesser spotted eagle (''Aquila pomarina''), typical clutch
Image:Columba livia nest 2 eggs.jpg, Feral pigeon (''Columba livia domestica''), typical clutch
Image:Starling eggs.jpeg, European starling (''Sturnus vulgaris''), typical clutch
Image:Stieglitzgelege.jpg, European goldfinch (''Carduelis carduelis''), large clutch
Image:DesmognathusFuscusPageVA.jpg, Northern dusky salamander (''Desmognathus fuscus''), typical egg clutch
See also
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References
{{reflist, 30em
Birds
Bird breeding
Aviculture
Oology