Gut microbiota of urban birds

Junk-food has negative effects on the gut microbiota of urban birds

The specificities of life in cities can induce a number of modifications in urban-dwelling animal populations, which include changes in body size, physiology and behaviour. Researchers from the University of Antwerp (Erik Matthysen and Aimeric Teyssier, Global Change Ecology Centre, research group Evolutionary Ecology), together with colleagues from Ghent (Norraine Salleh Hudin, Luc Lens en Liesbeth De Neve) and Toulouse (Joël White), now show that urban habitats also impact the gut bacteria of sparrows.

The research shows that diet plays an important role in explaining the observed urban-rural differences and, more specifically, that low-fibre urban food reduces the diversity and the composition of the gut microbiota. The low gut diversity in urban birds even prevents them from benefiting from a high-fibre rural diet. The results, published in the journal Proceedings of the Royal Society B, thus suggest that the negative effects of low-fibre processed food on the gut microbiota as known in humans, may also occur in urban animals that feed on our waste.

To achieve these results, the researchers placed wild-caught urban and rural sparrows in aviaries and fed them with mimics of a low-fibre urban diet (cake, potato chips, bread) or of a high-fibre rural diet (wheat, sunflower seeds, mealworms). Aymeric Tessier, lead author of the study: “After 6 weeks, we found that the urban diet significantly reduced gut diversity and generally changed rural microbiota into typical urban ones. On the other hand, the rural diet increased gut diversity and changed urban microbiota into typical rural ones.”

However, urban birds only benefited from the more nutritious rural food when their gut diversity at the start of the experiment was high enough. These results suggest that the low diversity induced by urban life is likely to be associated with a loss of plasticity of the microbiota, thus hampering the urban’s bird ability to cope with diet change. A broader perspective brought by this study is that by giving urban dwellers access to processed, low-fibre food, the westernisation of human diets could possibly induce collateral effects on other species found in urban environments.