Egg tossing (behavior)
Encyclopedia
Egg tossing is a behavior observed in some species of bird
s and is related to infanticide
. The activity is performed so as to increase the chances that newly laid eggs
which are genetically closer to the female receive a better chance of survival. This behavior is often seen in species that exhibit cooperative breeding
.
During co-nesting
, before a bird starts laying its eggs, it tosses out some eggs laid previously by another bird. As a result, the last egg-layers may contribute more eggs to the common nest.
Among colonial
non-co-nesting birds egg-tossing is observed to be performed by conspecific (of the same species) intruders. The tossing observed was non-accidental: the intruder rolled the egg to the edge of the nest by repeatedly flicking it with its beak
.
It was concluded that in some species of cooperative birds egg-tossing is a strategy of clutch
coordination: eggs are tossed until all birds in the common nest are ready to proceed with brooding
, so that early egg-layers do not dominate the reproduction.
birds, such as some species of cuckoo
s: the cuckoo chick may toss host's eggs and even host's chicks out of the nest.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s and is related to infanticide
Infanticide (zoology)
In animals, infanticide involves the killing of young offspring by a mature animal of its own species, and is studied in zoology, specifically in the field of ethology. Ovicide is the analogous destruction of eggs. Although human infanticide has been widely studied, the practice has been observed...
. The activity is performed so as to increase the chances that newly laid eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
which are genetically closer to the female receive a better chance of survival. This behavior is often seen in species that exhibit cooperative breeding
Cooperative breeding
Cooperative breeding is a social system in which individuals contribute care to offspring that are not their own at the expense of their own reproduction . When reproduction is monopolized by one or few of the adult group members and most adults do not reproduce, but help rear the breeder’s...
.
During co-nesting
Nesting
Nesting refers to the process of efficiently manufacturing parts from flat raw material.Companies manufacturing parts from flat raw material such as sheet metal use a variety of technologies to perform this task. The sheet metal nesting for flat sheets and nesting for coils are different algorithms...
, before a bird starts laying its eggs, it tosses out some eggs laid previously by another bird. As a result, the last egg-layers may contribute more eggs to the common nest.
Among colonial
Bird colony
A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in close proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony...
non-co-nesting birds egg-tossing is observed to be performed by conspecific (of the same species) intruders. The tossing observed was non-accidental: the intruder rolled the egg to the edge of the nest by repeatedly flicking it with its beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
.
It was concluded that in some species of cooperative birds egg-tossing is a strategy of clutch
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
coordination: eggs are tossed until all birds in the common nest are ready to proceed with brooding
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
, so that early egg-layers do not dominate the reproduction.
Egg tossing by brood parasites
A slightly different behavior is that of brood parasiteBrood parasite
Brood parasites are organisms that use the strategy of brood parasitism, a kind of kleptoparasitism found among birds, fish or insects, involving the manipulation and use of host individuals either of the same or different species to raise the young of the brood-parasite...
birds, such as some species of cuckoo
Cuckoo
The cuckoos are a family, Cuculidae, of near passerine birds. The order Cuculiformes, in addition to the cuckoos, also includes the turacos . Some zoologists and taxonomists have also included the unique Hoatzin in the Cuculiformes, but its taxonomy remains in dispute...
s: the cuckoo chick may toss host's eggs and even host's chicks out of the nest.