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Urbanization and its impact on birds

Urbanization is rapidly expanding worldwide, and for wild animals this means both opportunities and challenges.

Urban-dwelling birds can benefit from the high abundance of anthropogenic foods, nest boxes for breeding and lower predation pressures (apart from areas where domestic cats are present). On the down side, the urban environment is associated with a number of environmental stressors (e.g. light, noise and air pollution) which pose physiological stress on urban-dwelling animals, including humans. 

In our research we aim to cover a broad range of questions related to the effects of urbanization on birds ranging from genetic polymorphism, gene expression and regulation through to physiological and ecological impacts. Some examples of our exciting work are detailed below.

In 2016 we published a paper in Biology Letters which revealed that growing up in an urban environment shortens the telomeres of nestling great tits, which have been suggested to be a predictor for longevity. Thus, this study suggests that factors in the urban environment have a negative impact on the longevity of great tits, and perhaps birds in general. Future studies are aiming to elucidate which environmental factors that may contribute to this effect.

Great tits

Furthermore, markers of oxidative stress are continuously used in our research. Oxidative stress is defined as an imbalance between pro-oxidants and antioxidants, with a surplus of the pro-oxidants, which cause declines in performance and increased risk of pre-mature death (two review papers has been published in this area, see BioScience and Ecology & Evolution). The urban environment can increase the oxidative stress in a number of ways. For example, nitrogen oxides (NOx) in traffic-fumes are directly active as pro-oxidants and certain urban food sources contain less dietary antioxidants. This topic was reviewed in a special issue on Urban Ecology in Functional Ecology (2015; see also EcoHealth for a meta-analysis). Currently, we are using epidemiological approaches to understand variation in oxidative stress along urbanization gradients. We are also investigating and disentangling the genetic and environmental influences on antioxidant defences.

Another large research area of the group is gene expression and gene regulation in relation to environmental stress and urbanization. A growing number of studies demonstrate that exposure to pollutants can cause long-term and trans-generational phenotypic effects, via oxidative stress, and thus epigenetics may play a key role in mediating effects of environmental stress exposure. Using urban and rural populations of a great tits, we currently investigate the role of DNA methylation in mediating the effects of exposure to urban stressors and aim to disentangle the links between oxidative stress, DNA methylation, genome stability (i.e. DNA damage and telomere attrition) and gene expression.

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Great tit food

Collaborators International

  • Alan Cohen
  • Cas Eikenaar
  • Andreas Nord
  • Mats Olsson