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The southern pied babbler (''Turdoides bicolor'') is a species of bird in the family
Leiothrichidae The laughingthrushes are a family, Leiothrichidae, of Old World passerine birds. They are diverse in size and coloration. These are birds of tropical areas, with the greatest variety in Southeast Asia and the Indian subcontinent. The entire fam ...
, found in dry
savannah A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...
of
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,
Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...
, and
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.


Description

The southern pied babbler is a medium-sized cooperatively breeding passerine bird. Groups range in size from 2-16 adults, but pairs are rare. The species is sexually monomorphic, with males and females indistinguishable from physical characteristics. Each group comprises a dominant breeding pair that monopolise access to breeding opportunities. Recent genetic research has confirmed that these dominant pairs are responsible for more than 95% of young hatched. Occasional mixed parentage has been observed, but is predictable in most cases: subordinates primarily gain parentage when a new (unrelated) immigrant disperses into the group, or a new group is founded. All group members cooperate to help raise the young hatched from a single clutch.
Clutch size __NOTOC__ A clutch of egg (biology), eggs is the group of eggs produced by birds, amphibians, or reptiles, often at a single time, particularly those laid in a nest. In birds, destruction of a clutch by predators (or removal by humans, for exam ...
varies between two and five, with a modal clutch size of three. Cooperative behaviours include: provisioning young (both in the nest and post-fledging), sentinel behaviour, territory border defense, teaching behaviour and babysitting behaviour (where semi-independent fledglings follow adults between foraging sites and away from predators). The breeding season extends from late-September to early April, although this varies between years and is strongly rain-dependent. Groups can raise up to three successful clutches per breeding season. Average incubation time is 14 days, and average time between hatching and fledging is 16 days. Fledging time varies according to group size: small groups tend to fledge their young earlier than large groups. Post-fledging, young are poorly mobile, unable to fly, and rely entirely on adult group members for food. Fledgling foraging efficiency develops slowly, and fledglings can continue to be provisioned by adults for up to four months post-fledging. The amount of care that young receive during this stage has long-term effects: fledglings that receive care for the longest periods tend to be heavier and better foragers than their counterparts. In addition, they are more likely to successfully disperse from their natal group and consequently begin reproducing earlier than their “failed-disperser” counterparts.


Behaviour

Aggression toward fledglings is most commonly observed when the dominant pair have begun to incubate another brood. During this period,
begging Begging (also panhandling) is the practice of imploring others to grant a favor, often a gift of money, with little or no expectation of reciprocation. A person doing such is called a beggar or panhandler. Beggars may operate in public pla ...
fledglings will be punished by parents using aggressive behaviour such as jumping on the youngster. In all cases, fledglings stop begging immediately following attack. Brood overlap results in a distinctive division of labour, with subordinate adults continuing to care for fledglings while the dominant pair concentrate their effort on the new brood. Owing to the extended period of post-fledging care in this species, this can result in dependent young from multiple broods being raised simultaneously. Pied babblers are strongly territorial, and defend their borders using wing and vocal displays on a near daily basis. These fights rarely lead to physical aggression and injury from such fights is very rare. Groups defend the same territory year-round and small groups tend to lose portions of their territory to larger neighbouring groups. Research on pied babblers has provided the first evidence of teaching behaviour in an avian species.Raihani, Nichola J. and Ridley, Amanda R.; “Experimental evidence for teaching in wild pied babblers”; in ''Animal Behaviour''; Volume 75, Issue 1, January 2008, pp. 3–11 Pied babblers teach their young by giving a specific purr call each time they deliver food. Young learn to associate this call with food and reach out of the nest each time they hear it. Adults exploit this association to encourage young to fledge by giving the purr call at a distance from the nest, enticing young to follow them. Post-fledging, adults continue to use the call to encourage young to move between foraging areas or away from predators. This call is also used to recruit independent fledglings to a rich foraging site, and may thus provide young with information on where to forage to locate rich food sources. Research on pied babblers has also provided evidence of task partitioning behaviour. In this species, the dominant pair are able to leave their dependent young in the care of helpers and initiate a new brood. This allows brood overlap: several broods of dependent young can be raised at the same time. Such a behaviour highlights the benefits of cooperative breeding: many helpers allow breeders to invest in more broods. Parents initiate this task partitioning by aggressively punishing offspring that beg at them for food.Raihani, N.J. & Ridley, A.R.; “Parental aggression against dependent young results in task partitioning in a cooperatively breeding bird”; ''Biology Letters'' 4 (2008), pp. 23-26. This repeated punishment results in young fledglings begging for food from helpers rather than their parents: freeing up their parents to breed again.


Interspecific interactions

Pied babblers have a complex interspecific interaction with the kleptoparasitic fork-tailed drongo, ''Dicrurus adsimilis''. Drongos perch above and follow babbler groups between foraging sites and give alarm calls each time a predator is seen. When drongos are present, babblers invest less time in sentinel behaviour. However, drongos occasionally give false alarm calls and then swoop down to steal the food items that the foraging babblers have dropped upon hearing an alarm call. To avoid the cost of
kleptoparasitism Kleptoparasitism (etymologically, parasitism by theft) is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct feeding, which can mean when ...
, large babbler groups, which have enough group members to participate in sentinel behaviour, do not tolerate drongos and aggressively chase them away from the group. Consequently, they suffer very few losses to kleptoparasitic attack. However, small groups do not have enough group members to provide sentinel behaviour without affecting time invested in other behaviours such as foraging or provisioning young. These groups therefore tolerate occasional kleptoparasitic attacks in return for the sentinel duties that drongos provide. Young pied babblers have difficulty handling larger food items such as scorpions, skinks and solifuges, and take a lot longer to break these food items down than adults.Ridley, A.R. and Child, M.F.; “Specific targeting of host individuals by a kleptoparasitic bird”; ''Behavioral Ecology & Sociobiology'', 63 (2009), pp. 1119-1126 This makes them ideal victims for attacks by fork-tailed drongos: research has revealed that drongos specifically target young babblers for kleptoparasitic attacks and gain greater foraging success by doing so.


The Pied Babbler Research Project

The Pied Babbler Research Project was established by Dr Amanda Ridley in 2003 for the purpose of studying many aspects of cooperative breeding behaviour over the long-term. The population comprises fully habituated groups of wild pied babblers. The average number of groups in the population varies between 10-18 each year. Research is conducted continuously by scientists and postgraduate students and involves investigations into population dynamics, the causes and consequences of helping behaviour, sexual selection, foraging ecology, interspecific interactions, vocal communication, parent-offspring conflict, kin recognition, maternal effects, physiology and reproductive conflict.Ridley, Dr. Amanda
“Pied Babbler Research Project”
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Inbreeding avoidance

Individuals appear to avoid inbreeding in two ways. The first is through dispersal, and the second is by avoiding familiar group members as mates. Although both males and females disperse locally, they move outside the range within which genetically related individuals are likely to be encountered. Within their group, individuals only acquire breeding positions when the opposite-sex breeder is unrelated. In general,
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders a ...
is avoided because it leads to a reduction in progeny fitness (
inbreeding depression Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...
) due largely to the
homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...
expression of deleterious recessive alleles.


Gallery

File:Recently fledged.jpg, Pied babblers fledge their young when they are still unable to fly. File:Pied babbler sentinel.jpg, Pied babblers display cooperative sentinel behaviour, with individuals foregoing foraging to act as watchmen for the rest of the group. This is usually done high up in exposed locations. When they spot a predator they give alarm calls to alert the rest of the group to the type of threat. File:Adult plumage.jpg, Pied babbler adults have a white head and body with dark brown rectrices and remiges. File:Pied babbler in flight.jpg, In flight File:Fledgling beg.jpg, Pied babbler fledglings form short-term associations with foraging adults, where they follow and beg to gain food. Fledglings occasionally fight with their siblings over access to an adult. File:Fledgling plumage.jpg, Pied babblers initially fledge with completely brown plumage, this slowly moults and fledglings have a mottled appearance before they gain full adult plumage. File:Pied babbler group.jpg, Pied babbler group File:Provision.jpg, All members of a pied babbler group help to provision offspring produced by a single dominant pair. File:Pied babblers playing.jpg, Pied babblers have ample leisure time which they fill with games of chasing, hanging upside down, play-fighting and jumping on each other. File:Pied babbler foraging.jpg, Pied babblers spend >90% of their foraging time on the ground. Their diet consists mainly of invertebrates, which they either glean from the surface or dig up.


References


Further reading

* Collar, N. J. & Robson, C. 2007. Family Timaliidae (Babblers) pp. 70–291 in; del Hoyo, J., Elliott, A. & Christie, D.A. eds. ''
Handbook of the Birds of the World The ''Handbook of the Birds of the World'' (HBW) is a multi-volume series produced by the Spanish publishing house Lynx Edicions in partnership with BirdLife International. It is the first handbook to cover every known living species of bird. ...
'', Vol. 12. Picathartes to Tits and Chickadees. Lynx Edicions, Barcelona. * (Southern) Pied Babbler
Species text in The Atlas of Southern African Birds


External links

* * {{Taxonbar, from=Q1304486
southern pied babbler The southern pied babbler (''Turdoides bicolor'') is a species of bird in the family Leiothrichidae, found in dry savannah of Botswana, Namibia, South Africa, and Zimbabwe. Description The southern pied babbler is a medium-sized cooperatively b ...
Birds of Southern Africa
southern pied babbler The southern pied babbler (''Turdoides bicolor'') is a species of bird in the family Leiothrichidae, found in dry savannah of Botswana, Namibia, South Africa, and Zimbabwe. Description The southern pied babbler is a medium-sized cooperatively b ...
Taxonomy articles created by Polbot