Jan-Åke Nilsson



The general framework for my research is how differential investment into reproduction and survival forms different life history strategies. Individuals have to make decisions about how to allocate limited resources, such as energy and time, between different actions, as the resources invested in reproduction can not at the same time be invested in survival. Such trade-offs are the corner-stone of life history theory. To understand how evolution has formed such strategies, I am interested in the role of physiological adaptations and constraints.

Life history strategies are chosen by individuals to maximize life-time reproductive success. This will be achieved by optimal trade-offs e.g. how much effort should be invested in reproduction vs. survival or is it better to produce many small or a few large offspring. Such trade-offs are dependent on functional adaptations as well as constraints. Functional mechanisms, for example related to energy turnover rates, resistance to infections and parasites and the action of hormones, interact with the environment to form individually optimised life history strategies. Thus, the internal state of the individual will limit the possible strategies open for that individual. Especially, the body temperature and the risk of overheating, may constitute such an internal state that potentially can reduce work rate and thereby investment in current reproduction.

Furthermore, parasite resistance and hormones may be transferred to the young from their mother through the egg, thereby influencing the phenotype of the next generation. A mother’s ability to provide their young with a good start in life is probably also dependent on her quality and condition, in turn dependent on physiological as well as ecological constraints.

Human impact can of course affect these trade-offs and I am therefore also interested in how human activities and urbanisation might affect the life-history trade-offs.

Another, related line of research is about adaptations to winter in sedentary birds. Here, metabolic rate, body temperature and fat reserves will combine to form a strategy that minimises the risks of starvation and predation during long winter nights.

Most of my work is based on field experiments performed in the wild with principal study organisms being nest box breeding birds. However, I sometimes also work with captive zebra finches.

Recent research outputs

Koosje P. Lamers, Nicolaus, M., Rakhimberdiev, E., Jan Åke Nilsson & Both, C., 2020 Feb, In : Journal of Avian Biology. 51, 2, e02190.

Research output: Contribution to journalArticle

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