Long-term study of great reed warblers
Studying selection in the wild
All breeding individuals of a socially polygynous population of great reed warblers at Lake Kvismaren, southern Central Sweden, have been monitored annually since 1983. Based on high between-year return rate of both juveniles and adults and a comprehensive data set of traits and fates of each territorial male and breeding female, we are able to study what determines lifetime breeding success in the population. This includes studying female mate choice, causes of and responses to nest predation, and trait variation that affect breeding success.
Since 1987, we have collected blood samples from all adults and chicks in the area that now are used for genetic analyses. Based on this extensive genetic material (>3000 individuals), we can determine the genetic parentage of chicks allowing us to build a very good pedigree as well as identify extra-pair young and determine their true parents. This allows us to investigate patterns of ongoing selection in the wild (and potential for microevolution).
Sex differences in immune (MHC) gene variation
We are also conducting a project on sex-specific effects of costs and benefits of immune (MHC) gene variation. We use our unique long-term data set of the great reed warblers at Kvismaren, which provides us with very good estimates of lifetime reproductive success. Based on new next-generation sequencing techniques to identify MHC alleles and thus score number of alleles and antigen recognition repertoire of individual great reed warblers, we are analysing sex-specific patterns of effects of immune gene diversity.
Ageing in the wild
We study life history strategies and ageing patterns and assess how different intrinsic and external factors (such as disease, reproductive effort, genetic background, nestling performance and early life characteristics) contribute to accelerated ageing. In particluar, we aim to better understand the role of telomere shortening in age-related changes in life history traits in the great reed warbler.
Song and fitness
Song is a key factor to understand the behaviours and life histories of passerine birds. Research over the last 20-30 years have shown that song produced by male birds is important both in male-male competition over territories and for female attraction. We have been studying song in great reed warblers since 1985. In Kvismaren, great reed warbler males spend the entire daylight period (20-21 hours) producing song until pairing with a female.
We have found that male song repertoire size (i.e. number of different sounds a male sings) is an important trait predicting his harem size (number of breeding females on his territory) and his extra-pair fertilization success. Male song repertoire size increases with age and is higher among males hatched in our study area. It also seems to reflect genetic qualities because males with larger song repertoire sizes produce offspring with higher post fledging survival. We have recently been involved in developing an automated equipment to compare and measure song traits, using the great reed warbler song as an example.
Since 2008, we use geolocators to study the migration ecology of great reed warblers that breed in Kvismaren (southern Central Sweden) and winters in tropical Africa. Our aims with this study are to study migration and wintering ecology, and to connect migration with breeding to study carry-over effects (including mechanisms mediating such effects) between years, as well as between spring and autumn.