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Decline of house sparrows due to lack of overwinter food

August 28, 2002

The decline of the house sparrow in rural areas of Britain over the past two decades has possible occurred because of reduced food supplies, leading to localised extinctions, according to a report by Oxford zoologists published tomorrow [29 August 2002] in Nature.

Dr David Hole and colleagues in the Farmland Bird Group at Oxford University`s Edward Grey Institute of Field Ornithology studied populations of house sparrows in the Oxfordshire area, collecting a variety of demographic data and undertaking genetic analyses.

They found evidence that some sparrow populations may be unable to sustain themselves due to a limited supply of food over winter - likely to be a result of changes in farming practice including a switch from spring to autumn sowing of cereals, and cleaner farmyards with bird-proof storage of grain. Where populations have declined to extinction, migration between remaining populations is likely to be reduced as a result of the greater separation between them. Declining or extinct populations may therefore not be recolonised, compounding the problem.

Dr Hole said: `The decline of the house sparrow, at least in rural areas, may not stop unless measures to provide food resources, particularly over the winter, are implemented. However, a variety of agri-environment schemes, recently adopted by the Department for Environment, Food and Rural Affairs (DEFRA), may well be a positive move in this direction.`

Future research is now likely to focus on the causes of the declines that have taken place in many of our major cities - which may also be related to reduced food availability, compounded by other factors.

Oxford, University of