Pied Babbler Research Project

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 (principal investigator)

Members of the research project

Dr Nichola Raihani, Institute of Zoology London, UK
Dr M.B.V. Bell, Cambridge University, UK
Dr Martha Nelson-Flower (recent PhD graduate)
Krystyna Golabek (PhD student, external)
Alex Thompson (MSc student)
David Humphries (PhD student, external)
Fiona Finch (field assistant)

Research Collaborators

Prof. T.H. Clutton-Brock, Cambridge University, UK.
Prof P.A.R. Hockey, Percy Fitzpatrick Institute, University of Cape Town
Prof. A. Zahavi, Tel Aviv University, Israel.
A/Prof S. C. Griffith, Macquarie University, Australia

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.

Dr Amanda Ridley (Principal Investigator)

(Macquarie University Research Fellow, and Honorary Research Associate at the Percy FitzPatrick Institute)

Mandy's homepage | Email: amanda.ridley@mq.edu.au or amanda.ridley@uct.ac.za

My research interests are varied, and range from long-term research that has been conducted since the start of the research project seven years ago, and short-term current research such as central-place foraging experiments and analyses into patterns of sexual selection.

The causes and consequences of helping behaviour

All pied babblers contribute to all cooperative activities, including incubation, provisioning young and territory defense. However, some group members help significantly more than others and may thereby incur a greater cost of helping, potentially affecting condition and future reproductive success. One of my main aims when I first started the babbler project was to look at the long-term effects of the cost of helpers, and the consequences of helping behaviour. These consequences include not only the survival and development of young, but also impacts on the survival, fecundity and longevity of the dominant breeding pair compared to subordinate helpers, as well as the opportunities for subordinates to gain a dominant position. Since pied babblers are such long-lived birds (we have several individuals that are at least eight years old), it requires many years of research to get to the bottom of this question. The project is now at the stage where it is producing truly valuable data on the consequences of helping behaviour, and I am currently working on major analyses regarding this question using the long-term database.

Another of my aims was to gain measures of body mass from all individuals in the population on a daily basis, to be able to compare changes in mass to variation in patterns of helping behaviour. This is because although helping is assumed to be a costly activity, it is often difficult to prove this empirically without direct measures of mass changes in relation to levels of helper contributions. To date, the project now has over 20 000 pied babbler weight records with which to address this question. We have monitored individual weight variations right from hatching, through juvenile development, time as a helper, attainment of dominance, to death. My aim over the next year is to pull all this data together, combined with several experiments and individual profiles of foraging efficiency (a reflection of an individual’s contribution relative to the cost of helping), to be able to get at the causes and consequences of helping behaviour in pied babblers.

The battle of the females: sexual selection

I have recently embarked on a new area of research that looks at sexual selection strategies and their consequences on group dynamics, social matings, reproductive success and dispersal patterns in the Pied Babbler. This research is being supported in part by the National Geographic Society. I started this research based on observations of the unusually ferocious behaviour of adult females. In pied babblers, females may invest in very lengthy and costly fights with one another, sometimes losing up to 20% of body mass in the process. These fights can end up with one bird being evicted from a group and territory. This is bad news for babblers: they have very poor survival rates as floaters and are often in very bad condition. So why do females invest in such costly fights? There is a surprising trend in female ferociousness: they most often fight for heavy, ‘sexy’ dominant males. Light males are often completely ignored, even when there is a breeding position available. I am using a series of experiments to investigate:

• how females identify the difference in quality among males
• how males effectively advertise their quality (or hide their ‘lack of quality’)
• how females assess their chances of winning against a rival or resident female once they do locate a ‘sexy’ male
• what effect male quality has on female dispersal, mating and divorce patterns
• what the benefits are of mating with a ‘sexy’ male (e.g. level of care provided to young, offspring quality, effective territory defense, acquisition of good quality territory, ability to retain helpers)

Other areas that I am interested in, and currently do active research on include: central-place foraging, kin recognition, population dynamics, life history strategies, sex ratios patterns in relation to preferential care, and cooperative influences on reproductive success (in terms of critical group size and ecological versus social effects).

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

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?

Dr Nichola Raihani

(Postdoctoral Research Fellow, Institute of Zoology, London)

Nichola's homepage | Email: nichola.raihani@ioz.ac.uk

I conducted my PhD research on pied babblers at the Department of Zoology, Cambridge University. My PhD thesis was entitled 'cooperation and conflict in pied babblers'. I currently co-supervise a PhD student with Phil Hockey (Alex Thompson, UCT) who is working on parent-offspring conflict in pied babblers. For more information on my research interests, please see my webpage at the Institute of Zoology, London.

Dr Martha Nelson

(Recent PhD graduate, Centre of Excellence at the Percy Fitzpatrick Institute, University of Cape Town)

Martha's homepage | E-mail: marthajn@hotmail.com

I recently successfully completed my thesis on ‘kinship and its consequences in the cooperatively breeding Pied Babbler’ at the University of Cape Town. A major component of my thesis was using genetic analyses to successfully describe the breeding system of pied babblers for the first time, helping us to corroborate behavioural patterns with genetic patterns of relatedness. In addition, I investigated inbreeding, the occurrence of sex-biased dispersal, reproductive conflict and kin selection. Currently, I am assisting Mandy on-site with her research on sexual selection in pied babblers.

Krystyna Golabek

(PhD student, School of Biological Sciences, University of Bristol, UK)

Krystyna's homepage | E-mail: krystyna.golabek@bristol.ac.uk

Alex Thompson

(Masters student, Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town)

Alex's homepage | Email: alex.thompson@uct.ac.za

Maternal effects on parent-offspring conflict in the cooperatively breeding Pied Babbler

There is commonly a struggle between parents and offspring over the allocation of resources (Trivers 1974). Parents have a finite amount they can invest over their lifetime and, all else being equal, are selected to distribute available resources equitably among both current and future young. Offspring, on the other hand, are more related to themselves as individuals, than they are to their siblings and so are expected to try and monopolise an unequal share of parental investment (PI). This sets up a conflict between parents and offspring over the allocation of care, parent-offspring conflict (POC). In most studies, the effects of pre-hatching / pre-birth maternal investment have been ignored, despite the fact that investment at this stage can have marked consequences for offspring fitness. In order to fully understand the struggle between parents and offspring, PI at all stages of development must therefore be measured.

Cooperatively breeding species offer several advantages for empirical studies of POC. Firstly, cooperatively breeding species commonly have overlapping broods of young which allows us to directly measure how investment in one brood affects investment in subsequent broods, without any time delay. Secondly, in cooperatively breeding species, offspring typically have extended periods of care, allowing us to measure how investment and associated POC change over several stages of development. Finally, maternal investment might be particularly variable and therefore amenable to study in cooperatively breeding species. Key research questions are:

• What maternal egg- investment strategies are used and how do these change between and within broods?
• What are the consequences of egg investment for chick development, growth and survival?
• What factors affect chick begging vocalisations?
• How do provisioners respond to chick begging?
• How do provisioning strategies affect offspring fitness?

David Humphries

(PhD student, School of Biological Sciences, Macquarie University)

David's homepage | Email: david.humphries@students.mq.edu.au

Pied Babbler Research Project Publications

Publication list [PDF]