Lights and shadows of city life: Consequences of urbanisation for oxidative stress balance of the house sparrow

Urban expansion constitutes a big challenge for wildlife. Urban areas have been designed for humans, causing other animal species that share these spaces with them having to cope with, and adapt to, the presence of humans and the consequences of its activities. However, some animal species have been attracted by these new ecosystems and the opportunities it offers. The house sparrow (Passer domesticus L.) is a species traditionally linked to human settlements. It has been considered well adapted to humanised environments, but, in recent decades, the house sparrow is suffering a strong decline in some of the most urbanised areas of Europe.
The reason for this decline remains unclear, but high pollution and low food quality in urban areas have been suggested as potential causes. I studied oxidative stress to analyse the consequences of urbanisation for house sparrow populations. The results obtained suggest the population decline may be related to the cost of city life in terms of oxidative stress: high pollution levels in urban habitats exert pressure on the antioxidant defences of individuals; moreover, food sources common in the city (e.g. processed food leftovers) have a negative effect on the provision of essential nutrients and may enhance the generation of free radicals.
The implementation of policy changes in cities, such as reducing pollution and conducting campaigns on how to feed wildlife may contribute to halting the decline of urban house sparrow populations.