Causes of population decline of urban house sparrows

In London, sparrow numbers fell by 60% between 1994 and 2004. The house sparrow is now on the red list of conservation concern and a priority BAP species. Research in London and Leicester is trying to identify causes of the urban sparrow decline.

• To identify environmental factors which have caused or contributed to the decline of house sparrow populations in towns and cities.

• Starvation of chicks due to lack of invertebrate prey was found to be the main cause of high levels of chick mortality in a declining suburban sparrow population in Leicester.
• Supplementary feeding of mealworms increased nesting success (fledglings produced per nesting attempt) by 55% in Leicester.
• Supplementary feeding of mealworms at 66 colonies in London increased breeding success (by 62%) but only had a small positive impact on colony size (adult abundance). Additional supplementary feeding of seed had no impact on the abundance of fledglings or adult sparrows. There seemed to be plenty of unoccupied suitable nesting sites in the London study areas.
• Food availability is probably not the main cause of the decline in urban sparrow populations.
• Management to enhance invertebrate availability in towns and cities is likely to boost house sparrow breeding success. However, such management is unlikely to lead to a recovery in breeding populations.

Further aspects of the study are currently being written up.

• Natural England 
• Institute of Zoology

 

• Bird guide: house sparrow