page_title: Egg tossing (behavior)
section_title: Egg tossing by brood parasites
hierarchical_section_title: Egg tossing (behavior) / Egg tossing by brood parasites
caption_attribution_description: English: Eastern Phoebe (Sayornis phoebe) nest with one Brown-headed Cowbird (Molothrus ater) egg
context_page_description: Egg tossing or egg destruction is a behavior observed in some species of birds where one individual removes an egg from the communal nest. This is related to infanticide, where parents kill their own or other's offspring. Egg tossing is observed in avian species, most commonly females, who are involved with cooperative breeding or brood parasitism. Among colonial non-co-nesting birds, egg-tossing is observed to be performed by an individual of the same species, and in the case of brood parasites this behavior is done by either the same or different species. The behavior of egg tossing offers its advantages and disadvantages to both the actor and recipient.
context_section_description: There are several species that will increase their offspring's chance of survival through a means that is slightly different than egg tossing, which is brood parasitism. These species will lay their eggs in nests of different species, allowing the offspring to survive without their direct contributions. Some bird species that exhibit this behavior are the Black-headed duck, the common cuckoo and cowbirds. There are two types of brood parasitism; one which the females lay their eggs in the nest of the same species and one where the eggs are laid in the nest of a different species.
  The common cuckoo is a species of cuckoo that exhibits brood parasitism in the nest of a different species. They accomplish this by watching the nest of a potential host and once the host leaves the nest the female cuckoo will remove one of the host's eggs and will replace it with one of their own. The female cuckoo will have no part in taking care of her offspring, instead she will leave the host's nest and look for another nest which she can lay more eggs. The common cuckoo will often stay in the nest and take advantage of the feeding of the host mother, even after the cuckoo is much larger and evidently not the host's offspring.
  A common species nest that the cuckoo will choose to place its eggs in, is the Reed Warbler.  The common cuckoo distinguishes the warblers nest and will choose what specific nest to brood in depending on the foliage and distance from the nest.
  The common cuckoo demonstrates the egg tossing behavior when they are just hatchlings. Once the cuckoo eggs are placed into the host nest and they hatch, they will evict the other species eggs out of the nest by pushing them out with their backs. This behavior is very beneficial for the cuckoos survival as they are able to grow and feed without any competition from other members of the nest.
  The cowbird is another parasitic species that lays their eggs in a different species' nest; the eastern phoebe.  Although the cowbirds eggs differ in size and colour, the eastern phoebe will still choose to provide parental care unless there is a partial clutch reduction, or PCR.
  There are different methods that brood parasites trick the host in raising their child, however some host's have developed counter adaptations to these. The adaptation between the host and brood parasites is an example of co-evolution.
caption: Brown headed cowbird egg in an eastern phoebe nest
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