Helpers at the nest

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. This phenomenon was first studied in birds where it occurs most frequently, but it is also known in animals from many different groups including mammals and insects. It is a simple form of co-operative breeding.

It occurs in between three and eight percent of bird species worldwide (estimates vary), but is much more common in Australia and Southern Africa.[1][2] Bird species in which this behaviour is found include the common moorhen, the acorn woodpecker, and the apostlebird. The sugar glider and humans are examples of mammals that exhibit this behaviour. It is also seen in a number of species of bee such as carpenter bees (note this is distinct from the behaviour of the European honey bee, where the worker bees are sterile and incapable of reproducing).

The term "helper" was coined by Alexander Skutch in 1935[3] 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.[4]

Three explanations for the occurrence of helpers at the nest have been put forward; they are not mutually exclusive, and in any particular species an investigation of the exact benefits and costs will be needed to see what combination of these factors may have driven the evolution of helping.[5]

  • Advantage to the helpers, who may be protected from predation, or gain skills that they will need when they subsequently reproduce, as a result of staying in the parental nest.
  • Kin selection: since subsequent litters or broods from the same parents will be full siblings to the helpers, they are as closely related genetically as their own offspring would be. Helping their parents is therefore as productive for the juveniles as reproducing themselves would be, and if their parents are better able to reproduce, the balance of advantage may be greater.
  • Delayed advantage to the helpers, in particular because they stand to inherit their parents' territory; this explanation is particularly compelling if suitable territories are in short supply, but requires specific quantitative conditions to be met, favouring a stable queue of potential heirs.[6]

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.[7] Extrapair mates are chosen by the females and are these then contribute to the care of the young who may be sired by them.[8]

Juveniles living in association with their parents cannot automatically be regarded as helpers. In a number of species, such as the logrunners[9] 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.

References

  1. ^ Jetz, Walter; Rubenstein, Dustin R. (2011). "Environmental Uncertainty and the Global Biogeography of Cooperative Breeding in Birds". Current Biology. 21 (1): 72–78. doi:10.1016/j.cub.2010.11.075. PMID 21185192.
  2. ^ McMahon T.A. and Finlayson, B. (1992) Global Runoff: Continental Comparisons of Annual Flows and Peak Discharges, Catena Verlag, ISBN 3-923381-27-1
  3. ^ Skutch, A. F. (1935). "Helpers at the nest" (PDF). Auk. 52 (3): 257–273. doi:10.2307/4077738.
  4. ^ Brown, J. L. (1978). "Avian communal breeding systems". Annu. Rev. Ecol. Syst. 9: 123–155. doi:10.1146/annurev.es.09.110178.001011.
  5. ^ Dickinson, J. L.; Hatchwell, B. J. (2004) "Fitness consequences of helping" in Ecology and evolution of cooperative breeding in birds by Walter D. Koenig, Janis L. Dickinson. Cambridge University Press. ISBN 978-0-521-53099-6
  6. ^ Wiley, R. H.; Rabenold, K. N. (1984). "The evolution of cooperative breeding by delayed reciprocity and queuing for favorable social positions" (PDF). Evolution. 38 (3): 609–621. doi:10.2307/2408710. Archived from the original (PDF) on 2010-06-17.
  7. ^ Ligon, J. D.; Burt, D. B. (2004) "Evolutionary origins" in Ecology and evolution of cooperative breeding in birds by Walter D. Koenig, Janis L. Dickinson. Cambridge University Press. ISBN 978-0-521-53099-6
  8. ^ Rubenstein, DR (2007). "Female extrapair mate choice in a cooperative breeder: trading sex for help and increasing offspring heterozygosity". Proceedings of the Royal Society B. 274 (1620): 1895–1903. doi:10.1098/rspb.2007.0424. PMC 2270931. PMID 17526455.
  9. ^ Frith, C.B., Frith, D.W. & Jansen, A. (1997). "The nesting biology of the Chowchilla Orthonyx spaldingii (Orthonychidae)". Emu. 97: 18. doi:10.1071/MU97002.CS1 maint: Multiple names: authors list (link)
Aegithalidae

The bushtits or long-tailed tits, Aegithalidae, are a family of small, drab passerine birds with moderately long tails. The family contains 13 species in four genera, all but one of which are found in Eurasia. Bushtits are active birds, moving almost constantly while they forage for insects in shrubs and trees. During non-breeding season, birds live in flocks of up to 50 individuals. Several bushtit species display cooperative breeding behavior, also called helpers at the nest.

Alexander Skutch

Alexander Frank Skutch (May 20, 1904 – May 12, 2004) was a naturalist and writer. He published numerous scientific papers and books about birds and several books on philosophy. He is best remembered ornithologically for his pioneering work on helpers at the nest.

Alloparenting

Alloparenting (also referred to as alloparental care) is a term used to classify any form of parental care provided by an individual towards a non-descendant young. Non-descendant refers to any young who is not the direct genetic offspring of the individual, but does not exclude related young such as siblings or grandchildren. Individuals providing this care are referred to using the neutral term of alloparent (or 'helper').Alloparental care encapsulates a diverse range of parenting systems across a range of animal groups and social structures. The alloparent-young relationship can be mutualistic or parasitic, and between or within species. Cooperative breeding, joint brood care, reciprocal allonursing, brood parasitism and cuckoldry represent situations in which alloparenting plays a role.

Bell miner

The bell miner (Manorina melanophrys), commonly known as the bellbird, is a colonial honeyeater endemic to southeastern Australia. The common name refers to their bell-like call. "Miner" is an old alternative spelling of the word "myna" and is shared with other members of the genus Manorina. The birds feed almost exclusively on the dome-like coverings, referred to as "bell lerps", of certain psyllid bugs that feed on eucalyptus sap from the leaves. The psyllids make these bell-lerps from their own honeydew secretions in order to protect themselves from predators and the environment.

Bell miners live in large, complex social groups. Within each group there are subgroups consisting of several breeding pairs, but also including a number of birds who are not currently breeding. The nonbreeders help in providing food for the young in all the nests in the subgroup, even though they are not necessarily closely related to them. The birds defend their colony area communally aggressively, excluding most other passerine species. They do this in order to protect their territory from other insect-eating birds that would eat the bell lerps on which they feed. Whenever the local forests die back due to increased lerp psyllid infestations, bell miners undergo a population boom.

Carsten Schradin

Carsten Schradin is a Swiss researcher of eco-physiology at the CNRS, IPHC, and DEPE. He became known for the study of Four-striped grass mouse in Succulent Karoo, South Africa. There, he discovered that the mice at that place were 10 times larger than those in the rest of South Africa. In 1999 he and Gustl Anzenberger have discovered that prolactin is connected with paternal care in various species of fish, birds, and mammals including primates. In 2016 he, along with his colleagues from Strasbourg, Jean Yves Georges and Pierre Ulrich have studied turtles in Alter Rhein.

Co-operation (evolution)

In evolution, co-operation is the process where groups of organisms work or act together for common or mutual benefits. It is commonly defined as any adaptation that has evolved, at least in part, to increase the reproductive success of the actor's social partners. For example, territorial choruses by male lions discourage intruders and are likely to benefit all contributors.This process contrasts with intragroup competition where individuals work against each other for selfish reasons. Cooperation exists not only in humans but in other animals as well. The diversity of taxa that exhibits cooperation is quite large, ranging from zebra herds to pied babblers to African elephants. Many animal and plant species cooperate with both members of their own species and with members of other species.

Cooperative breeding

Cooperative breeding is a social system characterized by alloparental care: offspring receive care not only from their parents, but also from additional group members, often called helpers. Cooperative breeding encompasses a wide variety of group structures, from a breeding pair with helpers that are offspring from a previous season, to groups with multiple breeding males and females (polygynandry) and helpers that are the adult offspring of some but not all of the breeders in the group, to groups in which helpers sometimes achieve co-breeding status by producing their own offspring as part of the group's brood. Cooperative breeding occurs across taxonomic groups including birds, mammals, fish, and insects.Costs for helpers include a fitness reduction, increased territory defense, offspring guarding and an increased cost of growth. Benefits for helpers include a reduced chance of predation, increased foraging time, territory inheritance, increased environmental conditions and an inclusive fitness. Inclusive fitness is the sum of all direct and indirect fitness, where direct fitness is defined as the amount of fitness gained through producing offspring. Indirect fitness is defined as the amount of fitness gained through aiding related individuals offspring, that is relatives are able to indirectly pass on their genes through increasing the fitness of related offspring. This is also called kin selection.For the breeding pair, costs include increased mate guarding and suppression of subordinate mating. Breeders receive benefits as reductions in offspring care and territory maintenance. Their primary benefit is an increased reproductive rate and survival.

Cooperative breeding causes the reproductive success of all sexually mature adults to be skewed towards one mating pair. This means the reproductive fitness of the group is held within a select few breeding members and helpers have little to no reproductive fitness. With this system, breeders gain an increased reproductive fitness, while helpers gain an increased inclusive fitness.

Corvidae

Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers. In common English, they are known as the crow family, or, more technically, corvids. Over 120 species are described. The genus Corvus, including the jackdaws, crows, rooks, and ravens, makes up over a third of the entire family.

Corvids display remarkable intelligence for animals of their size and are among the most intelligent birds thus far studied. Specifically, members of the family have demonstrated self-awareness in mirror tests (European magpies) and tool-making ability (e.g., crows and rooks), skills which until recently were thought to be possessed only by humans and a few other higher mammals. Their total brain-to-body mass ratio is equal to that of non-human great apes and cetaceans, and only slightly lower than that of humans.They are medium to large in size, with strong feet and bills, rictal bristles, and a single moult each year (most passerines moult twice). Corvids are found worldwide except for the tip of South America and the polar ice caps. The majority of the species are found in tropical South and Central America, southern Asia and Eurasia, with fewer than 10 species each in Africa and Australasia. The genus Corvus has re-entered Australia in relatively recent geological prehistory, with five species and one subspecies there. Several species of raven have reached oceanic islands, and some of these species are now highly threatened with extinction or have already become extinct.

Ibisbill

The ibisbill (Ibidorhyncha struthersii) is a bird related to the waders, but sufficiently distinctive to merit its own family Ibidorhynchidae. It is grey with a white belly, red legs and long down-curved bill, and a black face and black breast band. It occurs on the shingle riverbanks of the high plateau of central Asia and the Himalayas.

Orange clownfish

The orange clownfish (Amphiprion percula) also known as percula clownfish and clown anemonefish, is widely known as a popular aquarium fish. Like other clownfishes (also known as anemonefishes), it often lives in association with sea anemones. A. percula is associated specifically with Heteractis magnifica and Stichodactyla gigantea, and as larvae use chemical cues released from the anemones to identify and locate the appropriate host species to use them for shelter and protection. This causes preferential selection when finding their anemone host species. Although popular, maintaining this species in captivity is rather complex. The Great Barrier Reef Marine Park Authority regulates the number of collection permits issued to aquarium fish dealers who seek this, and other tropical fish within the Great Barrier Reef Marine Park.

The symbiosis between anemonefish and anemones depends on the presence of the fish drawing other fish to the anemone, where they are stung by its venomous tentacles. The anemone helps the fish by giving it protection from predators, which include brittle stars, wrasses, and other damselfish, and the fish helps the anemone by feeding it, increasing oxygenation, and removing waste material from the host. Various hypotheses exist about the fish's ability to live within the anemone without being harmed. One study carried out at Marineland of the Pacific by Dr. Demorest Davenport and Dr. Kenneth Noris in 1958 revealed that the mucus secreted by the anemone fish prevented the anemone from discharging its lethal stinging nematocysts. A second hypothesis is that A. percula has acquired immunity towards the sea anemone’s toxins, and a combination of the two has been shown to be the case. The fish feed on algae, zooplankton, worms, and small crustaceans.

Rarotonga monarch

The Rarotonga monarch (Pomarea dimidiata), also known as the Rarotonga flycatcher and kakerori, is a species of bird in the monarch flycatcher family Monarchidae. It is endemic to the Cook Islands.

Rhabdomys

Rhabdomys is a largely Southern African genus of muroid rodents slightly larger than house mice. They are known variously as striped or four-striped mice or rats. Traditionally the genus has been seen as a single species, Rhabdomys pumilio, though modern evidence on the basis of karyotype and mtDNA analysis suggests that it comprises two or more species and subspecies. Dorsally Rhabdomys species display four characteristic black longitudinal stripes on a paler background.

Screaming cowbird

The screaming cowbird (Molothrus rufoaxillaris) is an obligate brood parasite belonging to the family Icteridae and is found in South America. It is also known commonly as the short billed cowbird.

Southern ground hornbill

The southern ground hornbill (Bucorvus leadbeateri; formerly known as Bucorvus cafer), is one of two species of ground hornbill, which are both found solely within Africa, and is the largest species of hornbill worldwide. It can be found in the southern regions of Africa, ranging from Kenya to South Africa. Within these regions, they inhabit both woodlands and savannas. The other species of the genus Bucorvus found in Africa is the Abyssinian ground hornbill, B. abyssinicus.

Southern ground hornbills are carnivorous and mostly hunt on the ground, where they find the majority of their food. This food ranges from insects to small animals. Their nests are often found in high in tree cavities or other shallow cavities, such as rock holes in cliff faces. These birds are a long lived species, having lifespans in the range of 50-60 years, and up to 70 in captivity. In relation to their long lives, they do not reach sexual maturity until 4-6 years old, and begin breeding around 10 years old. Their sex can be identified by the color of their throats, where the male’s is pure red and the female’s is a deep violet-blue.Southern ground hornbills are a culturally pervasive and important species in southern Africa. Kruger National Park, located within South Africa, lists southern ground hornbills as one of their ‘Big Six’ bird species. However, their numbers have been declining, due in part to persecution, habitat destruction, cultural beliefs, and other factors. They are listed globally as ‘Vulnerable’ by the IUCN as of 2018, and ‘Endangered’ in South Africa, Lesotho, Namibia and Swaziland.

Stripe-backed wren

The stripe-backed wren (Campylorhynchus nuchalis) is a bird found in the savannas of northern Colombia and central Venezuela. It lives in dry, riparian woodland, or farmlands, and is found at heights up to 800 m.

The stripe-backed wren has attracted considerable scientific attention because it is a good example of co-operative breeding. It lives in groups ranging from 2 to 10 adult birds. Of these, only one pair breeds, laying eggs at the beginning of the rainy season (May to September). However, all members of the group participate in defence of the territory, and in feeding the young both in the nest and after fledging. They therefore qualify as helpers at the nest.

The non-breeding members of the group are usually offspring or siblings of the current breeding parents. After one or two seasons, females normally leave their natal groups and join another nest as helpers, typically in a neighbouring territory. Males, however, usually remain at their natal nest and if they survive will inherit the position of breeding male (though under some circumstances they too disperse). If the current breeding male dies or is removed, the next oldest male in the group normally takes over its position.

This breeding system may have evolved as a result of kin selection, but in addition it has been shown by Wiley and Rabenold (1984) that the males' behaviour of "queueing" for the status of breeding male can be an evolutionarily stable strategy provided some plausible conditions are met. Formally, the situation has the characteristics of a prisoner's dilemma game that is played repeatedly between the same partners, and in this case "defection" - jumping the queue - would not be advantageous.

Some of the calls of stripe-backed wrens show individual variations that are consistent from father to son. This is a potential example of the formation of a dialect in bird song. The distinctive family calls seem to be used to maintain social contact between members of the co-operatively breeding group.

As would be expected in a species where both sexes share in parental care, the stripe-backed wren shows no sexual dimorphism in appearance.

Taiwan blue magpie

The Taiwan blue magpie (Urocissa caerulea), also called the Taiwan magpie, Formosan blue magpie (Chinese: 臺灣藍鵲; pinyin: Táiwān lán què), or the "long-tailed mountain lady" (Chinese: 長尾山娘; pinyin: Chángwěi shānniáng; Taiwanese Hokkien: Tn̂g-boé soaⁿ-niû), is a species of bird of the crow family. It is endemic to Taiwan.

The Trials of Life

The Trials of Life: A Natural History of Behaviour is a BBC nature documentary series written and presented by David Attenborough, first transmitted in the United Kingdom from 3 October 1990.

A study in animal behaviour, it was the third in a trilogy of major series (beginning with Life on Earth) that took a broad overview of nature, rather than the more specialised surveys of Attenborough's later productions. Each of the twelve 50-minute episodes features a different aspect of the journey through life, from birth to adulthood and continuation of the species through reproduction.

The series was produced in conjunction with the Australian Broadcasting Corporation and Turner Broadcasting System Inc. The executive producer was Peter Jones and the music was composed by George Fenton.

Part of David Attenborough's 'Life' series, it was preceded by The Living Planet (1984) and followed by Life in the Freezer (1993).

Wayanad laughingthrush

The Wayanad laughingthrush (Pterorhinus delesserti) is a species of laughingthrush in the family Leiothrichidae. It is endemic to the Western Ghats south of Goa in India. These laughingthrushes move in groups in dense forests, producing loud calls but tend to be hard to spot in the undergrowth. They have brown upperparts, a white throat, a broad black mask through the eye and a heavy bill with pale yellow on the lower mandible. Despite the name, derived from the Wayanad region, this species has a wider range than the two other south Indian species of laughingthrush that are restricted to the higher elevation hills.

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