The Sparrow Weaver Project
The Sparrow Weaver Project
SOCIAL EVOLUTION & AGEING IN THE KALAHARI DESERT
40 SOCIAL GROUPS | LIFE-LONG SOCIAL PHENOTYPING
GENETIC PEDIGREE | TELOMERE BIOLOGY | GENOMIC TOOLS
White-browed sparrow weavers live in cooperatively breeding families of 2-14 birds.
The dominant pair in each group monopolise reproduction, while non-breeding subordinates cooperate to rear their young.
We continuously monitor the life-histories, social behaviour and genetics of >40 cooperative families in the spectacular Tswalu Kalahari Reserve. This is our major model system for research on Social Evolution & Ageing.
See below for more information on this extraordinary model system.
Current research projects include:
- The Evolution of Cooperation in Variable Environments
- The Origins of Individual Variation in Cooperative Behaviour
- Prospecting and Dispersal Strategies
- Selection on Inbreeding and Outbreeding
- Telomere Biology and the Mechanisms of Senescence
- Social Effects on Senescence
- Weaving Traditions and Culture
JOIN US: I am always keen to broaden the scope of the project, so if you’d like to discuss a potential collaboration
or pursue an MRes, PhD or Post-doctoral Fellowship using the sparrow weaver system, just drop me a line
THE BIG QUESTIONS
The Evolution of Cooperation in Variable Environments
Globally, cooperative breeding is associated with arid regions with highly variable rainfall regimes, suggesting that cooperation may yield particular benefits in such environments. Our long-term field research on sparrow weaver societies in the Kalahari is investigating whether this is the case and why. We use both ecological and molecular methods to investigate selection on cooperation in this wild population.
The Origins of Individual Variation in Cooperative Behaviour
We are investigating how genetics and the early life environment interact to shape cooperative tendencies in sparrow-weaver societies, using our long-term social and environmental data, genetic pedigree and genomic tools. We are also investigating the role that trade-offs with other traits may play in generating individual variation and sex differences in cooperation, and the emergence of alternative life-history trajectories.
Parental Plasticity in Variable Environments
While some parents have no helpers to assist with nestling care, others have up to 12. We are combining natural observations with field experiments to investigate how and why mothers adjust egg size and both parents adjust their nestling care contributions according to availability of helpers.
Reproductive Conflict, Dispersal and Inbreeding
The dominant breeding pair monopolise reproduction within groups, and while ~15% of offspring are sired by extra-group males, these too are sired by dominants. As <10% of adult birds ever become dominant and tenures can exceed 12 years, this species shows extraordinary variance in reproductive success in both sexes. We are therefore interested in the dispersal strategies that subordinates use to maximise their chances of winning dominance, and how sexual and kin selection interact to shape the traits that lead to dominance. We are also investigating the impacts of their extremely local dispersal on patterns of inbreeding and tactics that mitigate inbreeding depression.
Social Effects on Life-histories
We use a range of molecular methods to investigate the impacts of cooperation and social conflict on rates of somatic deterioration. And we are interested more broadly in the impacts of extreme reproductive skews and helping on the evolution of lifespans in such highly cooperative organisms.
Biogeography and Speciation
The are four sub-species of white-browed sparrow weavers ranging from Equatorial Africa in Ethiopia through to the Temperate zone in South Africa. We are exploiting the differences among these to ask questions about the genetic and behavioural mechanisms that may facilitate speciation by maintaining trait divergence during sub-species contact.
A HIGHLY TRACTABLE MODEL SYSTEM
We have been monitoring the lives of >40 cooperatively breeding groups of white-browed sparrow weavers in a single continguous population in the spectacular Tswalu Kalahari Reserve, in the Northern Cape province of South Africa.
Several factors leave this an unusual tractable system for Evolutionary and Mechanistic research:
We are able to monitor complete life-histories
The system is ideal for studying early-life and maternal effects on adult physiology & behaviour, as the birds’ year-round territoriality and local dispersal allow us to monitor them from the Egg through to Cooperation, Dispersal, Reproduction and Senescence…
The birds can be readily caught from their roost chambers
As all group members sleep alone each night in their conspicuous woven roost chambers we can catch any given bird on any given evening. This makes the system unusually tractable for molecular research and other studies that require precisely timed or repeated longitudinal captures of known individuals. This also facilitates the sampling over larger spatial scales that underpins our biogeographic research (see below). We now have > 10,000 capture records for our study birds since 2007.
Their natural nests are easy to locate, access and study
Their natural woven nests are conspicuous and can be readily accessed for monitoring laying, hatching and nestling growth, behaviour and physiology. This approach avoids the deviations from natural ecology that commonly accompany nest-box deployments. We fit transponder-reading antennae to the nests to automate the monitoring of cooperative behaviour, and are also studying the birds’ weaving behaviour and culture.
Automated monitoring of Parental and Cooperative Behaviour
We use an automated transponder reading system to collect detailed information on the cooperative contributions of all group members to the rearing of broods. This is allowing us to investigate the origings of the marked individual variation in cooperative contributions to helping in this species, the role of trade-offs with other fitness-maximising tactics, and the parental modulation of pre- and post-natal investment in young according to the availability of help.
Molecular Tools: Pedigree | 30,000 SNPs | Genome | Telomere biology | Oxidative stress | Endocrinology
Our diverse evolutionary and mechanistic questions demand the use of a range of molecular methods, including microsatellite and Rad-Seq SNP genotyping (for parentage assignment, pedigree building and direct estimates of relatedness and heterozygosity), telomere length quantitation (for ageing studies) and assessments of both the oxidative and endocrine states of birds. We now have a complete genetic pedigree for the population covering the first decade of the study, >200 birds genotyped at >30,000 SNPs, and a genome assembly in preparation.
Climate and habitat monitoring
In order to understand variation in cooperation, parenting, dispersal and settling decisions it is important to understand how territory quality and environmental conditions interact to influence reproductive decisions and success. We therefore continuously monitor the local climate and maintain tree, grass cover and ranging behaviour information on a GIS.
Logistics: A remote fieldsite with direct access & good facilities
Our fieldsite is situated in the spectacular Tswalu Kalahari Reserve in the Northern Cape province of South Africa. The site can be reached using the Reserve’s direct flights from Johannesburg airport, which land 15km from our basecamp in the southern part of the park.
Our basecamp sits in the shade of the Korranaberg hills and comprises a collection of accommodation units each with its own communal kitchen, office and ablutions. We have power, hot water, cell coverage, Wi-Fi, and standard freezers as well as facilities for the cryogenic storage of samples in liquid nitrogen. We source our supplies from well stocked stores around an hour’s drive away.