In Britain, house sparrow numbers have declined steeply in both urban and rural areas. London's sparrow population has dropped by sixty percent during the past six years. In rural areas of Britain, populations have fallen the same amount over the past thirty years.

Despite widespread public concern about shrinking house sparrow populations, scientists could not pinpoint the cause of the decline. But now, Mark Whittingham and his colleagues at the University of Oxford have uncovered one possible explanation—intensified agricultural practices.

Whittingham and his colleagues found that although the sparrows continue to produce the same number of young, fewer birds survive the winter. The team collected a variety of nesting and genetic information about the birds. They also provided food for the birds during winter months to evaluate the effects that food supply had on populations.

Whittingham and colleagues suggest that the crop stubble left in farm fields once provided a wintertime food source for the sparrows. But now, as farming trends have adopted autumn plantings, this food source has been drastically reduced. Sparrow populations experiencing food shortages experience drastic declines during winter months. Such populations must rely on an influx of birds from nearby farmlands in order to maintain a viable population. But as populations shrink, they become increasingly isolated and migration between populations becomes less common.

Although Whittingham and colleagues work reveals possible reasons for the decline of house sparrow numbers in rural areas, there has yet to be explanation for the dwindling urban populations of these birds.

The British government plans next year to launch a pilot study to encourage farmers to alter farming methods so as to benefit wildlife. Together, public concern, political planning, and scientific research are making the future of the rural house sparrow much brighter.

Find out more:

• Whittingham, MJ et al. 2002. Widespread Local House Sparrow Extinctions. Nature. 418:931.
• The British Trust for Ornithology. 2002. The Demography of Farmland Bird Population Changes.

Photo © Luis Cesar Tejo / Shutterstock. House Sparrow (Passer domesticus).