Dispersal through fitness landscapes in a social bird: from individuals to populations
Lead Research Organisation:
University of Sheffield
Department Name: School of Biosciences
Abstract
The effect of environmental variability on natural populations is perhaps the most pressing concern facing natural scientists. The distribution of populations is affected by spatial variation in their environment and the factors driving population change have been identified in many cases. However, it is individuals rather than populations that respond to variation in the environment that they encounter in their lives, and it is the consequences of these responses for individuals' capacity to survive and reproduce (i.e. their 'fitness') that determines what happens to their population at larger spatial scales. Therefore, to understand the processes through which spatial and temporal variation affects populations, there is an urgent need to understand the impact of that fine-scale variation on the behaviour, life history and ultimately the fitness of individuals.
The overall objective of this project is to fill this gap in knowledge by investigating the effect of fine-scale heterogeneity in the environment on the dispersal and evolutionary fitness of individuals in a population of social birds, and to use that understanding of individual responses to explain population-level effects. By studying a social species in which limited dispersal plays a vital role in the expression of kin-selected helping, we can also test the role of environmental heterogeneity in driving cooperation. The long-tailed tit is a small bird that exhibits a social system unique among UK bird species in which failed breeders often help close kin to raise their offspring. The behaviour, ecology and genetic composition of a population of individually marked birds living in a heterogeneous habitat has been closely monitored since 1994, providing a unique resource for this project. Direct fitness (from breeding) and indirect fitness (from helping) have been quantified for a large number of individuals using lifetime reproductive success data. Such detailed information on fitness is available for very few species, and in no other system has both direct and indirect fitness been quantified in this manner, offering us a unique opportunity to address these fundamental ecological issues.
The first objective of the project is to investigate how animals move along gradients in their environment. What factors do animals respond to when deciding to disperse from one place to another? There are essentially two kind of dispersal decisions. Natal dispersal is the movement from birthplace to the place of first breeding, while breeding dispersal is the movement observed between successive breeding attempts that may occur within the same breeding season or between seasons. Using long-term data and a modeling approach we will test hypotheses concerning the factors influencing individual movements within a variable environment.
The second objective is to conduct experimental manipulations of the social environment and of reproductive success to test whether there is a causal relationship between kinship and fecundity gradients and the natal and breeding dispersal decisions of individuals.
The third objective is to test the hypothesis that helping behaviour is a strategy that reduces the variation in fitness among individuals. In other words, helping is a risk-averse or bet-hedging strategy that individuals adopt at times or in places when the probability of gaining fitness directly (i.e. by reproduction) is low. In addition we will investigate the consequences of variation in individual fitness for population-level phenomena, testing the hypothesis that social species experience positive density dependence due to their social interactions.
Meeting these objectives will provide novel insights into the mechanisms through which individual-level responses to spatial and temporal environmental heterogeneity affect fitness and translate into population-level impacts, thereby addressing key gaps in our understanding of ecological processes.
The overall objective of this project is to fill this gap in knowledge by investigating the effect of fine-scale heterogeneity in the environment on the dispersal and evolutionary fitness of individuals in a population of social birds, and to use that understanding of individual responses to explain population-level effects. By studying a social species in which limited dispersal plays a vital role in the expression of kin-selected helping, we can also test the role of environmental heterogeneity in driving cooperation. The long-tailed tit is a small bird that exhibits a social system unique among UK bird species in which failed breeders often help close kin to raise their offspring. The behaviour, ecology and genetic composition of a population of individually marked birds living in a heterogeneous habitat has been closely monitored since 1994, providing a unique resource for this project. Direct fitness (from breeding) and indirect fitness (from helping) have been quantified for a large number of individuals using lifetime reproductive success data. Such detailed information on fitness is available for very few species, and in no other system has both direct and indirect fitness been quantified in this manner, offering us a unique opportunity to address these fundamental ecological issues.
The first objective of the project is to investigate how animals move along gradients in their environment. What factors do animals respond to when deciding to disperse from one place to another? There are essentially two kind of dispersal decisions. Natal dispersal is the movement from birthplace to the place of first breeding, while breeding dispersal is the movement observed between successive breeding attempts that may occur within the same breeding season or between seasons. Using long-term data and a modeling approach we will test hypotheses concerning the factors influencing individual movements within a variable environment.
The second objective is to conduct experimental manipulations of the social environment and of reproductive success to test whether there is a causal relationship between kinship and fecundity gradients and the natal and breeding dispersal decisions of individuals.
The third objective is to test the hypothesis that helping behaviour is a strategy that reduces the variation in fitness among individuals. In other words, helping is a risk-averse or bet-hedging strategy that individuals adopt at times or in places when the probability of gaining fitness directly (i.e. by reproduction) is low. In addition we will investigate the consequences of variation in individual fitness for population-level phenomena, testing the hypothesis that social species experience positive density dependence due to their social interactions.
Meeting these objectives will provide novel insights into the mechanisms through which individual-level responses to spatial and temporal environmental heterogeneity affect fitness and translate into population-level impacts, thereby addressing key gaps in our understanding of ecological processes.
Planned Impact
Who will benefit from this research, and how?
1. General public - Birds have a fascination for the general public in the UK, as evidenced by the mass membership of the RSPB (>1 million), the past inclusion of avian abundance in UK quality of life metrics, and the vast number of households that feed garden birds (c.12 million). An understanding of the impacts of environmental variation and climate change on bird populations will therefore be of interest for a substantial portion of the UK population, and, as a consequence, is likely to attract significant media attention.
2. School students with ambitions to become biologists - The proposal includes plans to develop links with a local sixth-form school that was established in a deprived area of Sheffield with the aim of nurturing academic students from disadvantaged socioeconomic backgrounds in order to enhance their opportunity to study at Russell Group universities. The aim will be to use this project and its field, lab and conceptual components as a vehicle to inform and enthuse students about scientific and environmental issues. In addition, members of the research team will provide mentoring activities to assist teaching staff and students interested in a biological career in university applications.
3. Conservation biologists and environmental managers - These two groups share an intense interest in assessing the mechanisms through which spatial and temporal changes to the environment influence biodiversity, and this issue lies at the heart of our research proposal. Most research in this area focuses on population-level responses, and understanding of the impact of the environment on individuals, or their movements within and between habitats lags well behind. We aim to redress this imbalance and demonstrate the potential for fine-scale environmental management to have significant consequences for populations. We will use CoI KLE's links with colleagues at the British Trust for Ornithology, RSPB and local wildlife trusts to ensure that the advances we make in understanding this relationship between fine-scale and population level effects are brought to a wide audience of environmental practitioners and policy advisers.
4. Human capital - The human capital impacts of this research will be substantial. The project brings together researchers with diverse and complementary skills that will build inter-disciplinary capacity within the University of Sheffield. More specifically, this project will foster links between behavioural, conservation and theoretical ecologists and mathematical biologists at a range of career stages, including a recently appointed lecturer (JRP) whose leadership and management of research will be enhanced through his involvement in the project. The PDRA will receive diverse training in field observation and experiments, mathematical ecology and the application of advanced statistical tools. The research technicians will gain extensive training both in techniques of field ornithology and also in molecular genetic analysis.
1. General public - Birds have a fascination for the general public in the UK, as evidenced by the mass membership of the RSPB (>1 million), the past inclusion of avian abundance in UK quality of life metrics, and the vast number of households that feed garden birds (c.12 million). An understanding of the impacts of environmental variation and climate change on bird populations will therefore be of interest for a substantial portion of the UK population, and, as a consequence, is likely to attract significant media attention.
2. School students with ambitions to become biologists - The proposal includes plans to develop links with a local sixth-form school that was established in a deprived area of Sheffield with the aim of nurturing academic students from disadvantaged socioeconomic backgrounds in order to enhance their opportunity to study at Russell Group universities. The aim will be to use this project and its field, lab and conceptual components as a vehicle to inform and enthuse students about scientific and environmental issues. In addition, members of the research team will provide mentoring activities to assist teaching staff and students interested in a biological career in university applications.
3. Conservation biologists and environmental managers - These two groups share an intense interest in assessing the mechanisms through which spatial and temporal changes to the environment influence biodiversity, and this issue lies at the heart of our research proposal. Most research in this area focuses on population-level responses, and understanding of the impact of the environment on individuals, or their movements within and between habitats lags well behind. We aim to redress this imbalance and demonstrate the potential for fine-scale environmental management to have significant consequences for populations. We will use CoI KLE's links with colleagues at the British Trust for Ornithology, RSPB and local wildlife trusts to ensure that the advances we make in understanding this relationship between fine-scale and population level effects are brought to a wide audience of environmental practitioners and policy advisers.
4. Human capital - The human capital impacts of this research will be substantial. The project brings together researchers with diverse and complementary skills that will build inter-disciplinary capacity within the University of Sheffield. More specifically, this project will foster links between behavioural, conservation and theoretical ecologists and mathematical biologists at a range of career stages, including a recently appointed lecturer (JRP) whose leadership and management of research will be enhanced through his involvement in the project. The PDRA will receive diverse training in field observation and experiments, mathematical ecology and the application of advanced statistical tools. The research technicians will gain extensive training both in techniques of field ornithology and also in molecular genetic analysis.
Organisations
Publications
Munden R
(2018)
Making sense of ultrahigh-resolution movement data: A new algorithm for inferring sites of interest
in Ecology and Evolution
Potts J
(2018)
Finding turning-points in ultra-high-resolution animal movement data
in Methods in Ecology and Evolution
Potts J
(2018)
Deciding when to intrude on a neighbour: quantifying behavioural mechanisms for temporary territory expansion
in Theoretical Ecology
Potts J
(2019)
Directionally Correlated Movement Can Drive Qualitative Changes in Emergent Population Distribution Patterns
in Mathematics
Williams HJ
(2020)
Optimizing the use of biologgers for movement ecology research.
in The Journal of animal ecology
Wilson RP
(2020)
An "orientation sphere" visualization for examining animal head movements.
in Ecology and evolution
Ellison N
(2020)
Mechanistic home range analysis reveals drivers of space use patterns for a non-territorial passerine.
in The Journal of animal ecology
Halliwell C
(2022)
Coordination of care by breeders and helpers in the cooperatively breeding long-tailed tit
in Behavioral Ecology
Sturrock N
(2022)
Who to help? Helping decisions in a cooperatively breeding bird with redirected care
in Behavioral Ecology and Sociobiology
Roper M
(2022)
Individual variation explains ageing patterns in a cooperatively breeding bird, the long-tailed tit Aegithalos caudatus.
in The Journal of animal ecology
Halliwell C
(2023)
Experimental variation of perceived predation risk does not affect coordination of parental care in long-tailed tits
in Behavioral Ecology and Sociobiology
Halliwell C
(2023)
Coordination of care is facilitated by delayed feeding and collective arrivals in the long-tailed tit
in Animal Behaviour
Description | We have completed a habitat map of the study site at high resolution. Dispersal movements of individuals across this landscape are currently being analyzed to determine the drivers of movement decisions. Fitness correlates of habitat variation has been anlayzed and movements in relation to fitness 'landscapes' investigated. |
Exploitation Route | Too early |
Sectors | Education Environment |
Description | The project has been used in outreach activities with a local sixth form college (Chapeltown Academy, Sheffield) to illustrate the scientific process. |
First Year Of Impact | 2019 |
Sector | Education |
Impact Types | Societal |
Title | GPS locations for mechanistic home range analysis reveals drivers of space use patterns for a non-territorial passerine |
Description | 1. Home ranging is a near-ubiquitous phenomenon in the animal kingdom. Understanding the behavioural mechanisms that give rise to observed home range patterns is thus an important general question, and mechanistic home range analysis (MHRA) provides the tools to address it. However, such analysis has hitherto been restricted to scent-marking territorial animals, so its potential breadth of application has not been tested. 2. Here, we apply MHRA to a population of long-tailed tits Aegithalos caudatus a non- territorial passerine, in the non-breeding season where there is no clear "central place" near which birds need to remain. The aim is to uncover the principal movement mechanisms underlying observed home range formation. 3. Our foundational models consist of memory-mediated conspecific avoidance between flocks, combined with attraction to woodland. These are then modified to incorporate the effects of flock size and relatedness, to uncover the effect of these on the mechanisms of home range formation. 4. We found that a simple model of spatial avoidance, together with attraction to the central parts of woodland areas, accurately captures long-tailed tit home range patterns. Refining these models further, we show that the magnitude of spatial avoidance by a flock is negatively correlated to both the relative size of the flock (compared to its neighbour) and the relatedness of the flock with its neighbour. 5. Our study applies MHRA beyond the confines of scent-marking, territorial animals, so paves the way for much broader taxonomic application. These could potentially help uncover general properties underlying the emergence of animal space use patterns. This is also the first study to apply MHRA to questions of relatedness and flock size, thus broadening the potential possible applications of this suite of analytic techniques. |
Type Of Material | Database/Collection of data |
Year Produced | 2020 |
Provided To Others? | Yes |
URL | http://datadryad.org/stash/dataset/doi:10.5061/dryad.fqz612jqj |
Title | Individual variation explains aging patterns in a cooperatively breeding bird, the long-tailed tit (Aegithalos caudatus) |
Description | 1. Alloparental care in cooperatively-breeding species may alter breeder age-specific survival and reproduction, and subsequently senescence. The helping behaviour itself might also undergo age-related change, and decisions to help in facultative cooperative breeders are likely to be affected by the individual condition. 2. Helpers in long-tailed tits (Aegithalos caudatus) assist relatives after failing to raise their own brood, with offspring from helped nests being more likely to recruit into the breeding population. 3. Using data collected over 25 years, we examined the age-trajectories of survival and reproduction in adult long-tailed tits to determine how these were affected by the presence or absence of helpers, and how helper behaviour changed with age. 4. There was evidence for increased reproductive performance with breeder age, but no effect of age on the probability of survival. We found no evidence of significant senescent decline in survival or reproductive performance, although individuals accrued less inclusive fitness in their last year of life. Lifetime reproductive success was positively related to both reproductive lifespan and body mass. Within a season, breeders that were assisted by helpers enjoyed greater reproductive success through enhanced offspring recruitment in the following year. We found no evidence that age affected an individual's propensity to help, or the amount of indirect fitness accrued through helping. 5. We found a positive correlation between lifespan and multiple components of reproductive success, suggesting that individual variation in quality underpins age-related variation in fitness in this species. Helping decisions are driven by condition, and the lifetime inclusive fitness of immigrants was predicted by body mass. These findings further support individual heterogeneity in quality being a major driver for fitness gains across the life course of long-tailed tits. |
Type Of Material | Database/Collection of data |
Year Produced | 2022 |
Provided To Others? | Yes |
URL | http://datadryad.org/stash/dataset/doi:10.5061/dryad.g79cnp5rz |
Title | Lifetime reproductive success and fitness estimates of long-tailed tits in the Rivelin Valley, Sheffield, UK, from 1994-2019 |
Description | Dataset comprising data on the lifetime reproductive success (LRS) of 879 individually marked long-tailed tits Aegithalos caudatus, a cooperatively breeding passerine. LRS is measured in terms of the number of local recruits into the breeding population in the study area, controlling for fledgling sex and extra-pair paternity. LRS data are then partitioned into direct and indirect fitness components, quantified as genetic equivalents. Partitioning of fitness follows Hamilton's definition of inclusive fitness: (a) direct fitness is measured as the production of offspring, stripped of the social effect of helpers on productivity; (b) indirect fitness is calculated from the mean marginal effect of a helper on productivity, adjusted for helper relatedness. Inclusive fitness is calculated by summing direct and indirect fitness. |
Type Of Material | Database/Collection of data |
Year Produced | 2022 |
Provided To Others? | Yes |
URL | https://catalogue.ceh.ac.uk/id/0e55f507-e5bd-4678-a5ea-8c3ffb62d3ac |