The latest research into the decline of the house sparrow points to shortage of insect food as a contributory factor.
The reasons for the decline of the house sparrow (
Passer domesticus) are known to be complex (see for example the
news item on 19th May 2005). A new PhD study by De Montfort University student Kate Vincent has thrown new light on the problem. Miss Vincent said
'This is one of the most mysterious and complex declines of a species in recent years. Since 1970 the house sparrow population has declined by 58% while sparrow populations in rural gardens have declined to a lesser extent, by only 48%. Many chicks starved during June and July before leaving the nest and a lack of small insects... was a particular problem in suburban areas'.
Fieldwork was undertaken at nine study areas across Leicester and surrounding villages, with more than 600 nest boxes erected. At each site the sparrows' nesting success, chick condition, diet and feeding habits were monitored.
Many chicks starved during June and July before leaving the nest and a lack of small insects, including beetles, craneflies and aphids, and spiders was a particular problem in suburban areas lacking deciduous trees, shrubs and long grass.
Miss Vincent said
'While we can't pinpoint one simple cause of sparrows' decline, food limitation during the breeding season does have a negative impact on nestling survival rates. House sparrows need key habitats in which to find food for their young during the summer breeding months and they particularly target deciduous shrubs, grass lawns and tilled soil. The trend for low maintenance and smaller gardens with more concrete, gravel, paving and evergreen shrubs, as well as the increased development of brownfield sites in city areas, could limit the availability of invertebrates. The loss of deciduous greenery from the suburban landscape may have made life much more difficult for birds like house sparrows that need large numbers of insects to feed their young.'
Dr Will Peach, Senior Research Biologist at the RSPB, said
'This study has clearly demonstrated that a lack of insects in suburbia during summer prevents house sparrows rearing their young. Although we are not sure about the exact causes of the population decline, any measures that boost insect numbers in gardens should help nesting sparrows. Growing deciduous shrubs and trees, leaving patches of unmown long grass and minimising usage of insecticides should all help.'
