Statistical Population Ecology


Andreas Lindén, Louise Lindroos (ÅAU), Sara Fraixedas (UH), Andreas Otterbeck (UO), Patrik Korn (ÅAU), Marianne Karlemo (ÅAU), Oscar Gordo (DBS)

ÅAU — Åbo Akademi University, UH — University of Helsinki, UO — University of Oslo (Norway), DBS — Doñana Biological Station (Spain)

We study questions in the field of population ecology, encompassing both applied and basic research. Statistical modelling has a central role in our work and often stands for part of its novelty. We aim to use sound models that give us as straightforward and reliable answers as possible to the questions studied. To bridge the gap between ecology and practical analyses, we think of stochastic models as integral parts of ecological theory.


Topics of interest in our research

Population dynamics and demography

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The core of our research is to enhance our understanding of the dynamics of natural populations. This topic is also central to conservation biology. We study how population processes vary in space and different habitats — something that helps us to understand how well earlier local results can be generalized. These questions often require statistical methods that acknowledge the uncertainty of population density estimates. I many cases, combining several complementary sources of data is effective for approaching yet unsolved questions.

Sara Fraixedas studies patterns and drivers of population trends in Finnish birds. She also constructs new indicators, which can be used for monitoring the states of bird communities in different habitats.

In her MSc thesis Marianne Karlemo aims to explain variation in the reproductive success of Willow Warblers in southern Finland, relating it to the timing of spring migration and earliness of spring. This common long-distance migratory species is strongly declining, but we do not know exactly why.

Besides our primary focus — bird populations — we now have a project studying how physical variables affect zoo- and phytoplankton population dynamics in the Baltic Sea. Here time-series models are applied to separating the stochastic population processes from observation and sampling noise. The project is run by Louise Lindroos, funded by Onni Talaan Säätiö, and conducted in close collaboration with the CZRT plankton project.

Study topics:

  • How do environmental variables affect natural populations?
  • How do bird population trends vary in space and between species?
  • Recognition of habitat specific population characteristics
  • Spatial patterns in demographic parameters
  • Ecological explanations to variable reproductive success


Bird migration and movement

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Migration behaviour is closely linked to dispersal and range shifts. Especially for populations living in a changing climate, understanding different aspects of migration can be vital for pinpointing conservation concerns. Changes in the timing of bird migration have recently been intensively studied and widely documented in many systems. However, it remains poorly understood how long-term phenological changes feed back on the species’ population dynamics. Further, measuring phenological change from noisy data is no trivial task, and the choice of a proper approach depends on the question studied.

Partial migrants, i.e. species whose populations contain both resident and migratory individuals, provide a great model system for studying the reasons for migration and why sexes and age classes may show differential migration. They also help us understanding the flexibility in migratory behaviour and the reactions to present and future climate change. In his MSc thesis, Andreas Otterbeck studies several partially migratory species, aiming to explain the annual variation in the proportion of wintering individuals.

Starting in autumn 2016, Dr. Oscar Gordo (Doñana Biological Station, Spain) will visit us for a six-month research stay. Our collaborative research will focus on analysing bird migration phenology and population trends using ringing data from Doñana — a hot spot for European migrating birds.

Study topics:

  • Using phenological functions for modelling seasonal migration
  • Migratory prolongation and opportunistic settling
  • What affects the overwintering proportion in partial migrants?
  • How does weather affect migration intensity?
  • What can we learn from bird observatory data?


Bioacoustic analysis and animal communication

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Animal sounds tell us more than we might expect at first thought. Birds’ song can reflect their motivation, condition or social status. Many sounds are individually specific, like fingerprints, and can be used for individual recognition from recordings. Such information can be utilized e.g. in mapping and surveys. To capture the relevant variation, bioacoustic data needs to be measured using several variables. Hence, multivariate statistics is the appropriate framework for analyses of bioacoustic data.

We run a field project collecting longitudinal data on Tawny Owl male territorial calls. Following the same individuals through time allows to more effectively separating individual level traits in vocalization from environmental induced variation and e.g. effects of ageing. Applying bioacoustic analyses, Patrik Korn does his MSc thesis about the level of territorial aggression in male calls, with an emphasis on identifying differences between colour morphs.

Study topics:

  • Tawny Owl vocalization in relation to its territorial behaviour
  • Spatial and heritable components in avian vocalization
  • Individual recognition and its applicability in surveys