Cooperative Breeding and Sociality in Birds:
Pied Babbler Research Project

Return to Cooperative Breeding and Sociality in Birds Research Programme

beginnings of a new project • what is the pied babbler? • the pied babbler research project • members of the research project • research opportunities • recent publications • media coverage • contact details • acknowledgements

Coordinator

Dr Amanda Ridley

The beginnings of a new project....

The Pied Babbler Research Project was established in 2003 and is the first major project to work with habituated groups of pied babblers. The project is now well-established with a number of habituated groups and several researchers working at the study site.

What is the pied babbler?

Young babblers are intensively cared for by adults for up to two months post-fledging

The pied babbler (Turdoides bicolor) is a medium-sized (75 - 95 g) passerine inhabiting semi-arid acacia savanna in the Kalahari Desert, southern Africa. The species is relatively terrestrial, foraging mainly on the ground and rarely flying more than a few hundred metres at a time. The diet of the pied babbler consists mainly of small invertebrates, although occasionally fruits and larger prey items such as lizards and scorpions are taken.

Pied babblers are obligate cooperative breeders that live in groups which occupy and defend territories year-round. Inter-group interactions are common and usually comprise of ritualized displays on territory borders, although displays may occasionally escalate into physical aggression. Most of the available habitat is occupied by babbler groups. Lone individuals, who are usually failed dispersers or individuals that have been evicted from a territory are rare, usually comprising less than 2% of the adult population.

Groups typically comprise between three and 14 adults, although groups with more than eight adult members are rare. Average group size during the breeding season is usually 4 – 5 adults 2 - 3 juveniles. Breeding typically occurs between October and March, and groups may produce up to three broods per year. Each brood usually consists of three eggs. Reproduction is usually dominated by a single breeding pair, with the rest of the group assisting to raise the brood produced from a single nest. In some groups, especially newly formed groups or groups that have recently experienced the death of a dominant individual, reproduction may be shared among several group members. Individuals may fight for access to breeding partners, and the result of such a conflict can often be death or eviction from the group.

Playfighting among broodmates is extremely common

The pied babbler breeding cycle, in common with many cooperative species, covers an extensive time period. Following nest-building, which can take up to four days, there is a two-week incubation period followed by two weeks in which chicks are fed at the nest. At fledging, chicks are unable to fly and continue to be reliant on adult group members for food for up to three months. During this period chicks will actively follow adult group members, begging loudly and often mimicking adult foraging techniques. Playfighting among fledglings is extremely common and can take numerous forms, some of which occasionally escalate into aggressive competitions for dominance. Adults will begin another breeding attempt before the previous clutch is entirely independent, and during this time adults may divide tasks up into those helping at the new nest and those helping fledglings from the previous clutch.

Each group has a stable dominance hierarchy. Dominance is observed through agonistic interactions, including pecking, guard replacement and physical aggression by dominant individuals, and submissive gestures, including posturing and imitating chick calls, by subordinate individuals. All groups members participate in numerous cooperative behaviours, including allopreening, incubating the brood, escorting young, guarding, leading groups between foraging areas, mobbing predators, provisioning young, removing faecal sacs from the nest, shading young from the sun, teaching young, and territory defence.

The Pied Babbler Research Project

Juveniles do not attain full adult plumage until up to eight months post-fledging

The Pied Babbler Research Project was set up by Dr Amanda Ridley with the purpose of studying social interactions among group members and the causes and consequences of helping behaviour. There are currently 12 colour-ringed groups on the project, with a further six peripheral groups that project members aim to incorporate into the main population. All groups have been habituated to allow close observation from a distance of approximately two to three metres without causing the birds any distress. The birds have been trained to jump on and off a top-pan balance for a small food reward. This allows researchers to monitor daily weight changes, which can be used to measure the cost of help, chick development, and many other aspects of behaviour in this species. Each group is observed at least once every three days, and consequently levels of habituation on the project continue to improve.

The Pied Babbler Research Project is located at the Kuruman River Reserve, in the southern Kalahari, South Africa. The reserves occupies approximately 25 km2 of semi-arid acacia savanna. Average rainfall is approximately 217 mm a year, although it is highly variable between years, with most rain concentrated in the summer months between October and March. The Pied Babbler Research Project occupies the same study site as the Kalahari Meerkat Project and has strong collaborative links with this project.

Since the successful establishment of a number of habituated groups, several research projects have begun on the pied babblers. Research continues year- round at the study site and descriptions of the specific interests of each project member are given below.

Members of the research project

amanda ridley • andrew radford • nichola raihani • martha nelson • krystyna golabek

Dr Amanda Ridley and Kito in the field.

Dr Amanda Ridley (Principal Investigator) DST/NRF Centre of Excellence Percy Fitzparick Institute of African Ornithology University of Cape Town email: amanda.ridley@.uct.ac.za Large Animal Research Group Department of Zoology University of Cambridge Further information on Mandy and her research >>

My main research interests focus on the following:

The causes and consequences of helping behaviour

Group members are weighed on a daily basis

In the pied babbler, all group members contribute to all cooperative activities, including incubation, provisioning young and territory defence. However, some group members help significantly more than others and may thereby incur a greater cost of help, potentially affecting condition and future reproductive success. I am investigating the causes for variation in helping behaviour by looking at relatedness among individuals, access to breeding partners, and the cost of help through individual weight loss and foraging efficiency. I am also looking at the consequences of help received on chick growth, development and fitness.

Preferential care and sex ratio manipulation

In most breeding attempts multiple chicks survive to fledging and aggressively compete for food from adult group members. Some adult group members show a preference for feeding certain chicks over others, in spite of the proximity of begging broodmates. I am investigating the causes of preferential care in this species with reference to sex ratio manipulation. Sex ratio has important consequences for group composition in the pied babbler as this species has sex-biased dispersal, with the males commonly remaining on the natal territory while females disperse to seek breeding positions elsewhere.

Babbler-drongo interactions

Drongos guard above foraging babbler groups and give alarm calls to alert the group to the presence of predators, although occasionally drongos will give false alarm calls to kleptoparasitise large food items that babblers catch. Both species gain some benefit from the interaction, although the level of benefit received by each species varies according to babbler group size. I am investigating a number of questions with regard to the complex interactions between these two species.

Other research

Other research I am involved in includes deception during territorial conflicts, critical group size, division of labour, sex differences and maternal effects.

Dr Andrew Radford hard at work again....

Dr Andrew Radford School of Biological Sciences University of Bristol Woodland Road Bristol BS8 1UG UK email: Andy.Radford@bristol.ac.uk Further information on Andy and his research >> See also: Cooperative Breeding and Sociality in Birds

My research focuses on how vocalisations are used to mediate conflicts and aid cooperation in social groups. I am using the pied babblers as a model system to investigate four main areas of interest.

Intra-group decision-making

Juveniles have a prolonged period of learning before attaining proficient foraging skills.

Many of the advantages of group living can only be fully realised when group members remain in close proximity and co-ordinate their actions. I am interested in whether babbler groups choose a new foraging site despotically or democratically, and whether individuals signal their readiness to leave as a reflection of their current foraging success. I am also examining the conflict apparent each evening when groups decide which roost site to use.

Intra-group foraging competition

Individuals of many group-living species produce and exchange frequent vocalisations when foraging, but the exact function of this very common social behaviour is often difficult to divine. Babblers produce two distinct calls while foraging: a contact call and a food-attraction call. I am using observations, playback experiments and supplementary feeding to discover the exact function of these calls, when they are given and which individuals respond to them.

Inter-group territorial contests

Group territorial displays are a prominent feature of many avian cooperative-breeding systems, but they have rarely been studied in any detail. I am using observational and playback data to assess the influence of group size and sex ratio on the vocal chorusing of pied babblers during their raucous territorial disputes. I aim to determine which individuals participate when and the types of call they give on different occasions. Furthermore, I am investigating the rules involved in the assessment of group resource-holding potential, and what determines the outcome and duration of contests.

Contextual vocal learning

As well as learning how to produce a particular sound, individuals have to learn when to give that sound and how to respond correctly when it is produced by others. I am investigating how the babblers learn the correct circumstances in which to give their different alarm calls. Moreover, I am examining how they learn to respond not only to conspecific alarm calls, but also those of crimson-breasted shrikes (which are reliable) and fork-tailed drongos (which use false calls to kleptoparasitise the babblers).

Nichola Raihani laughing in the face of data collection

Dr Nichola Raihani Large Animal Research Group Department of Zoology University of Cambridge email: nicholaraihani@yahoo.co.uk or njr29@cam.ac.uk

Attaining rank and reproductive status in the cooperatively-breeding pied babbler

Pied babblers are extremely cooperative, and regularly display affiliative behaviours, such as allopreening and huddling.

Cooperatively breeding species typically exhibit high levels of reproductive skew. In the extreme case, only the dominant pair breed and subordinate 'helpers' assist in rearing these (sometimes unrelated) offspring. In this 'winner takes all' system, one might expect that individuals are selected to maximise their chances of attaining and maintaining reproductive status in the group. Such selection is likely to act on a variety of levels and, in light of the above predictions, it makes sense to ask whether dominance hierarchies are simply borne out of differences in physical attributes between individuals, or whether individuals employ behavioural strategies to elevate their social standing. Despite over thirty years of research on cooperative breeding systems, few studies have investigated how such dominance hierarchies are formed and maintained, or whether tactics employed by individuals of different age, sex and dominance status affect their position in the hierarchy.

I will focus on behavioural tactics, specifically the use of social interaction type in the formation and maintenance of dominance hierarchies in the pied babbler. Social behaviours can broadly be classed as either affiliative (where there is no apparent 'loser' in the interaction or agonistic (where an individual's behaviour is detrimental to other group members). The importance of affiliative versus agonistic social interactions will be quantified in terms of their impacts on an individual's rank - in the struggle for dominance status is it better to be feared or loved?

Martha misreads the small print in her PhD contract...

Martha Nelson PhD student DST/NRF Centre of Excellence Percy Fitzpatrick Institute of African Ornithology University of Cape Town email: martha.nelson@uct.ac.za Further information on Martha and her research >>

Kin recognition: mechanisms and consequences

For cooperative breeders, recognition of one’s kin may be extremely important. The ability to discriminate between relatives and non-relatives could facilitate kin selection (when individuals help close family members to raise their offspring) and incest avoidance. I am interested in investigating kin recognition in the pied babblers to discover how they identify relatives and strangers. I will also be examining genetic parentage using molecular biology methods. How important is kin recognition in decisions concerning mate choice, helping, and control of the breeding system? I will be using a series of manipulations and playback experiments to explore recognition latency (‘out of sight, out of mind’), response to different calls (familiar relateds, familiar non-relateds, unfamiliar relateds and unfamiliar non-relateds), variation in kin recognition abilities between the sexes (since males are the philopatric sex, they may have better sibling recognition abilities than females), patterns of roving in relation to relatedness to focal group members, and the adaptive value of kin recognition (e.g. less energy spent in territory border conflicts with relatives). Molecular analyses will be a major component of this work.

Krystyna becomes part of the landscape...

Krystyna Golabek PhD Student School of Biological Sciences University of Bristol Woodland Road Bristol BS8 1UG UK email: Krystyna.Golabek@bristol.ac.uk

Vocal communication and social cognition in group-living societies

My interests lie in the complexity of vocal signalling in a social group. It has been widely accepted that signals can convey information about the signaller. Commonly explored are signals between parents and their offspring, and those between potential mates. Such signals have been shown to communicate information on recognition, need, location, and for the latter various cues on status, health and potential genetic quality. The signals within and between highly social group-living species has however had less attention. Where many individuals regularly interact, cooperate to raise young, coordinate to move around their territory and defend it against neighbouring groups, it may be evolutionarily beneficial to recognise individuals, group members, the sex or dominance status of individuals, as well as distinguish between your neighbours and strangers. In my research with the pied babblers I intend to understand the function and complexity of vocal signalling in a highly social species. My research splits into two main topics.

What information is transferred in vocal signals both within and between groups? For example;

• The call function
• The signal content, such as urgency, referential information, or signaller information such as sex, group, dominance or even self

How does that information influences the behaviour of the receiver? For example;

• Is there an effect of reliability in alarm calls and sentinel posts, and if so does the response behaviour vary accordingly?
• Is there an effect of social status in group coordination calls, do some individuals have more influence than others on group movements?
• Is there an effect of sex or dominance status in inter-group choruses? Does that influence response behaviour of, in particular, subordinates who have no reproductive opportunities within their own group?
• Is there an effect of familiarity in inter-group choruses, and how does that influence the response behaviour?

Recent Publications

Scientific publications

• Bell, M.B.V., Radford, A.N., Rose, R., Wade, H. M. & Ridley, A. R. 2009. The value of constant surveillance in a risky environment. Proceedings of the Royal Society B-Biological Sciences 276:2997-3005.
• Raihani, N.J. & Ridley, A.R. 2008. Experimental evidence for teaching in wild pied babblers. Animal Behaviour 75:36-11.
• Raihani, N.J. & Ridley, A.R. 2008. Parental aggression against dependent young results in task partitioning in a cooperatively breeding bird. Biology Letters 4, 24-26.
• Raihani, N.J., Ridley, A.R., Browning, L.E. & Nelson-Flower, M.J. 2008. Female-biased juvenile aggression in cooperatively breeding pied babblers. Ethology 114, 452-458.
• Ridley, A.R. and Raihani, N.J. 2008. Task partitioning increases reproductive output in a cooperative bird. Behavioral Ecology IP 080808.
• Ridley, A.R., Raihani, N.J. & Nelson-Flower, M.J. 2008. The cost of being alone: the fate of floaters in a population of cooperatively breeding pied babblers Turdoides bicolor. Journal of Avian Biology 39:389-392.
• Radford, A.N. & Ridley, A.R. 2007. Close-calling regulates spacing between foraging competitors in the group-living pied babbler. Animal Behaviour.  [PDF: Proof]
• Ridley, A.R. & Raihani, N.J. 2007. Facultative response to a kleptoparasite by the cooperatively breeding pied babbler. Behavioral Ecology 18, 324-330. [PDF]
• Radford, A.N. & Ridley, A.R. 2007. Individuals in social groups may use vocal cues when assessing their need for anti-predator vigilance. Biology Letters 3, 249-252.
• Ridley, A.R. 2007. Factors affecting offspring survival and development in a cooperative bird: social, maternal and environmental effects. Journal of Animal Ecology 76, 750-760.
• Ridley, A.R. & Huyvaert, K.P. 2007. Sex-biased preferential care in the cooperatively breeding Arabian babbler. Journal of Evolutionary Biology 20, 1271-1276.
• Ridley, A.R., Child, M.F & Bell, M.B.V. 2007. Interspecific audience effects on the alarm-calling behaviour of a kleptoparasitic bird. Biology Letters 3, 589-591.
• Ridley, A.R & Raihani, N.J. 2007. Variable post-fledging care in a cooperative bird: causes and consequences. Behavioral Ecology 18, 994-1000.
• Raihani, N.J. & Ridley, A.R. 2007. Variable fledging age according to group size: tradeoffs in a cooperative bird. Biology Letters 3, 624-627.
• Raihani, N.J. & Ridley, A.R. 2007. Adult vocalisations during provisioning: offspring responses and post-fledging benefits in wild pied babblers. Animal Behaviour 74, 1303-1309.
• Radford, A.N. & Ridley, A.R. 2006. Recruitment calling: a novel form of extended parental care in an altricial species. Current Biology 16, 1700-1704.