Ұяға көмектесушілер: әлеуметтік мінез-құлық және эволюциялық аспектілер

Helpers at the nest is a term used in behavioural ecology and evolutionary biology to describe a social structure in which juveniles and sexually mature adolescents of either one or both sexes remain in association with their parents and help them raise subsequent broods or litters, instead of dispersing and beginning to reproduce themselves. There are multiple proposed explanations for the behaviour, but its variability and broad taxonomic occurrences result in simultaneously plausible theories. The term "helper" was coined by Alexander Skutch in 1935 and defined more carefully in 1961 in the avian context as "a bird which assists in the nesting of an individual other than its mate, or feeds or otherwise attends a bird of whatever age which is neither its mate nor its dependent offspring." The term has been criticised as being anthropomorphic, but it remains in use. Other terms used especially in mammals, depending on the specific contexts, are non maternal (care by other than the mother), alloparental (care by other than the parents), cooperative (care by non breeding helpers) and communal (care by other breeding females) care.

It occurs in between three and eight percent of bird species worldwide (estimates vary), but is much more common in Australia and Southern Africa. Bird species in which this behaviour is found include the house sparrow, the common moorhen, the acorn woodpecker, and the apostlebird. Humans, damarland mole rats and meerkats are examples of mammals that exhibit this behaviour.

Although it is frequently assumed that helpers are non breeders, molecular evidence suggests that this may happen, and the term "secondary helper" is sometimes used in this case to indicate helpers that mate with or are not related offspring of the pair being assisted. The term "primary helper" being used for the commoner case of the helper being offspring of the pair and not involved in mating. Extrapair mates are chosen by the females and are these then contribute to the care of the young who may be sired by them. Juveniles living in association with their parents cannot automatically be regarded as helpers. In a number of species, such as the logrunners and the Siberian jay, young remain in the parental territory, but never help feed nestlings. However the delayed advantage explanation for the juveniles' association with their parents can still work in the absence of effective helping, whereas the kin selection explanation cannot.

Effects on reproductive success can be but are not always positive, and the strength of that positive correlation varies by species. Sometimes, the energy benefits to breeders, instead of being invested in improving reproductive performance, are used to offset reductions in reproductive performance. However, in many species, nestling survival rates are increased from helper investments. Further reproductive success benefits include better quality offspring,

Helpers at the nest can provide advantageous plasticity in the amount of investment parents need to give to their eggs and chicks. The presence of helpers can be associated with lower investments as the helpers can be depended on to provide certain elements of care and raising. This plasticity can be seen in reference to change in climate conditions. In unfavourable conditions there is a need for female parents to maintain high egg investment, but in favourable conditions, egg investment by mothers declines as helpers can assist with some of the care load. Superb fairy wrens with helpers at the nest see average egg sizes increase in dry and hot conditions and decrease in colder conditions compared to nests without helpers. A trade off of this increased survival over non helper juveniles is that their successful breeding rate after becoming helpers decreases compared to non helpers.