Brood parasite

Brood parasitism is the behavior of some animal species, not to incubate their eggs themselves, but by surrogate parents ( hosts ) to let hatch, the take over and the subsequent feeding and management of the most alien pups. Brood parasitism is primarily a birding technical term, but it is also used in other fields of zoology, such as entomology. In most cases leads to a reproduction brood parasitism disadvantage of host parents.

The brood parasites thus reduce their cost of parental care or parental care. This saves you the hassle of searching for food for their young, which allows them to find more food for themselves, and thereby lay more eggs. The disadvantage of this reproductive strategy is that some farmers recognize the alien nest and remove it either or start a completely new nest.

In German, parasitic animals often carry the additional name cuckoo ~, for example, the cuckoo duck, cuckoo bees or the cuckoo Fiederbartwels.

A distinction is made mainly of intraspecific and interspecific brood parasitism.

Intra -specific brood parasitism

In this variant of Parasitierens puts a female of a species its eggs in the nest of the same species Whether it beside himself also incubates a clutch, both individually and as a species-specific different. Intra -specific brood parasitism is difficult to prove, so that he might more common than previously thought. Many ducks and some colony breeders, such as the rook or some swallow species, at least occasionally show this behavior. Whenever clutches are unusually large, the Parasitierens consideration must be given to this form. Can be, however, the limits for Gemeinschaftsbrüten are sometimes fluent, so not always spoken by a parasitic, the chances of reproduction of the host -reducing behavior.

Inter -specific brood parasitism

When interspecific brood parasitism, the parasitic behavior is always observed. Usually only one egg per nest is placed. Grow the offspring in alien nests on, they are usually larger than males of the host parents and can even be significantly larger than their host parents themselves. This size advantage they get more food than the descendants of the host parents and are often shortly after hatching in a position to throw the other young birds and other eggs out of the nest, so that they stay alone in the nest.

Inter -specific brood parasitism may optionally or obligatorily occur.

Optional parasitic parents usually time their own nests, but increase their reproduction by forsaking eggs in host nests. The host parents pull the strange boys usually in addition to their own size, so that a strong synchronization between parasite and host is required in relation to egg size, incubation period and dietary habits.

Obligate brood parasites, of which are known so far about 80 species, serve not own nest. They lay their eggs singly, rarely in pairs, in the nests of the host parents, the selection of the hosts may be very different in both number and type. Some species, such as cowbirds, almost exclusively parasitize other blackbirds. All widow birds ( Viduinae ) parasitize single finch species ( Estrildidae ). Finch eggs and young are, however, not displaced by the hatching widow birds out of the nest. Rather, they grow together with her ​​step- siblings. They show not only the same body plumage, revenge drawing papillae or Schnabelrandwülste as young finches, but these same loud and in their mendicant movements. The specialization in certain types of hosts has advanced so far that successful males both their species-specific as well as dominate the singing of the host.

Similarly, all the representatives of the honey guide ( Indicatoridae ) appear to be obligate brood parasites.

Particularly successful interspecific brood parasitism in the bird family of cuckoos ( Cuculidae ) has been established, whose are about 140 species of obligate brood parasites than 50. Some other parasites while maintaining its own brood care only when a suitable opportunity, a behavior that is viewed as an evolutionary transition to obligate brood parasitism. In obligately parasitic cuckoos brutparasitierenden quality of behavior is very large because the eggs or the young of the hosts usually be removed from the laying females or later from just hatched parasites either. In addition many cuckoo species have a number of adaptations developed:

• Synchronization of ovulation: Probably the egg maturation is stimulated by observing the nesting activities of a potential host.
• Accelerated oviposition: When brood parasites lay their eggs must be done very quickly because the host parents could be sensitive to disturbances. Some cuckoo species can the finished egg in the fallopian tube store so that they can lay in the opportunity occurs very quickly.
• Egg size and Eiermimikry: Many cuckoos have their eggs in color and size matched those of the host parents. In this case, this adaptation seems highly dependent on the host from which the female parent was even hatched.
• Just hatched cuckoos some genera ( Cuculus, Caccomantis and Chrysococcis ) throw by certain paddling movements of the back eggs and young birds from the nest of the host parents. Some species have developed a small depression on the back.
• Especially the chicks of most parasitic cuckoo species, but also the chicks of some other brood parasites hatch after a shorter incubation period than that of the host parents and to grow, especially in the first few days approach very quickly. This gives them over the other nestlings a crucial feeding and growth advantage.

Josef Reichholf has taken the view that, when occurring in Europe cuckoo brood parasitism of evolutionarily emerged as a response to the competitive disadvantage compared to other by body size and construction of more efficient hunting techniques capable songbirds. Cuckoos therefore often feed of hairy caterpillars and butterflies toxic to be scorned by other songbirds, which they, however, could not feed their young. It also provides for the seizure of host eggs by cuckoo bird female ( as many as they themselves put in the same nest ) as former precursor of the current brood parasitism.

Probably watch some brood parasites after oviposition behavior of the host parents. Occasionally, it was found that nests and nests of the host parents were destroyed by the brood parasites when they removed the spurious egg.

Other types

Among the insect brood parasitism is widespread. For example, all wasps bees ( see also cuckoo bees) and some wasp species ( cuckoo wasps ) obligate brood parasites. Honey bees, which are due to their breeding biology known as cuckoo bees parasitize mainly sand bee species. Since most Wasps Bees are host specific, a strong increase of these insects lead to the collapse of stocks of host species, but this also attracts the local collapse of the parasitic nature to itself. Also among the hoverfly there are a number of obligate brood parasites, such as ( Volucella pellucens ), the Hummel - hoverfly.

The only fish, which is known to operate brood parasitism, are mainly occurring in Lake Tanganyika cuckoo Catfishes ( Synodontis multipunctatus and S. grandiops ) who foist their eggs mouthbrooding cichlids.