October 3, 2017
Despite being well-adapted to
urban life, house sparrow numbers are falling. A study in open-access
journal Frontiers in Ecology and Evolution finds that compared to
sparrows living in the country, urban-dwelling birds show clear signs of stress
linked to the toxic effects of air pollution and an unhealthy diet. This could
have health implications for people living in cities.
"We find that house sparrows
living in the city are suffering from more stress than those living in the
countryside, and we link this to differences in air quality and diet,"
says Amparo Herrera-Dueñas, who completed this work in collaboration with the
Department of Zoology and Physical Anthropology at the Complutense University
of Madrid, Spain.
"It is particularly bad for
urban birds during the breeding season when they are torn between allocating resources
towards fighting the toxic
effects of pollution or towards laying healthy eggs, both of
which aren't helped by their poor diet."
She adds, "If our cities are
unhealthy for birds, which is what our study is suggesting, then as their
neighbors we should be concerned because we are exposed to the same
environmental stressors as house sparrows."
Stress measured in urban,
suburban and rural sparrows
Herrera-Dueñas and her colleagues
used a non-invasive method to sample the blood of hundreds of sparrows from
rural, suburban and urban areas around the Iberian Peninsula in Spain.
"We took a small blood
sample from each bird, according to its weight and physical condition, and
released them unharmed," she explains. The samples were analyzed for signs
of oxidative
stress, which can be used to measure how much an environmental
stressor, such as pollution, is weakening the bird's natural defenses.
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