The Influence of Urban Environments on Oxidative Stress Balance: A Case Study on the House Sparrow in the Iberian Peninsula

Amparo Herrera-Dueñas,José I. Aguirre,María T. Antonio-García,Javier Pineda-Pampliega

doi:10.3389/fevo.2017.00106

Amparo Herrera-Dueñas, José I. Aguirre + Show 2 more

Open Access

https://doi.org/10.3389/fevo.2017.00106

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Abstract

The House Sparrow is a globally distributed species and is closely associated with anthropised environments. They are well-adapted to urban life; therefore the decline of their populations in Europe represents an unexpected event that demands an investigation into its causes. Causes that have promoted this decline are not well known, but one of the highlighted hypotheses is an increase of oxidative stress linked to the toxicity of pollution in urban areas. From an ecophysiological perspective, oxidative damage, antioxidant defence and oxidative balance are considered reliable indicators of environmental stressors such as pollutants. To carry out this study, blood samples were collected from House Sparrows in three different habitats that varied in terms of urbanisation degree: urban, suburban and rural; during the winter and breeding season. According to our results, urban sparrows showed higher levels of oxidative damage and higher activity of antioxidant enzymes, but lower antioxidant capacity in comparison with the rural birds; and these differences especially increase during the breeding season. The maintenance of oxidative balance increases in an urban environment in comparison to a rural one; we suggest that the high level of pollution and the poor quality diet linked to urban environments. The breeding season is expected to be particularly challenging for the oxidative balance of urban birds, when the reallocation of resources between self-maintenance and reproduction may be critical due to the scarcity of antioxidants found in urban areas. This study may contribute to determining the causes of the population decrease of House Sparrows in cities.

Highlights

Urban areas have been growing rapidly over the last several decades, and it is expected that they will continue to expand at the expense of natural and rural habitats
These areas are usually associated with high pollutant levels due to traffic and heater emissions. (II) Suburban, residential areas located at the edge of big cities and/or smaller towns
We found that urban sparrows showed higher levels of oxidative damage and a higher activity of antioxidant enzymes, but a lower antioxidant capacity in comparison with the rural birds

Summary

Introduction

Urban areas have been growing rapidly over the last several decades, and it is expected that they will continue to expand at the expense of natural and rural habitats. House Sparrow Coping with City novel and potentially stressful conditions generated by urban environment processes have provided new opportunities for certain species to gain an ecological advantage by exploiting city resources (Lepczyck and Warren, 2012; Costantini et al, 2014) Such resources are characterized by lower predation rates (Evans et al, 2015), higher environmental temperatures (Tryjanowski et al, 2015), lower competition for resources (Kark et al, 2007), and a constant, abundant, and more predictable food resources supply, in comparison with the surrounding non-anthropogenic areas (Shochat, 2004; Oro et al, 2013; Andersson et al, 2015; Tryjanowski et al, 2015; Marzluff, 2016). There is no consensus on the reason for such a decline, but the increasing level of pollution has been highlighted as one of the main driving factors (Shaw et al, 2008; Herrera-Dueñas et al, 2014)

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