The birds living in urban environments are more aggressive in defending their territory than their counterparts in rural areas, according to a study on the melodic sparrow (song sparrow) conducted in the United States, where it is a widespread species.

The increased aggressiveness of bird  city is due to have better food and shelter but also more competition to seize these resources, according to researchers at Virginia Tech (United States).

“The study comes to endorse what other research has already pointed out: cities may be hostile environments for birds,” he said in a statement the coordinator of the Monitoring SEO / BirdLife, Juan Carlos del Moral.

American scientists, whose study is published in the journal Biology Letters measured the level of aggressiveness of melodic playing a recording sparrow singing of these birds  and watching the reactions of the inhabitants of the area at the intrusion.

While in urban areas sparrows were closer to the speaker, flapping their wings “furiously” and joining the loud chanting speaker then start a trill duller which the researchers associated with an imminent attack, sparrows field the reaction did not occur so hard.

Health indicators of habitat

The urban birds, “health indicators of habitat” by SEO / BirdLife, have lost 18% of its population in the last twenty years so that ” it is necessary to ensure that cities and suburbs are friendly spaces” for biodiversity.

The impact of urban pollution on birds also affect their physical conditions, as indicated by a previous investigation carried out by the Complutense University of Madrid explaining that the health of the resident birds in the city was much worse than that of their peers peripheral or rural areas.

“Sparrows in central Madrid, for example, have anemia and defense systems seem altered,” he added del Moral, who said that breathe the same air pollution and are subject to the same level of noise that humans who work and they reside in the capital. “