Home > Our work > Science > Conservation Science in the RSPB > 2002 > Ecology of threatened species > Ecology and conservation of rural house sparrows
Ecology and conservation of rural house sparrows
The decline of house sparrows has generated intense public and media interest, helping to raise the profile of declining farmland birds.
With NERC, the RSPB co-funded a study of four farmyard house sparrow populations (A–D) in Oxfordshire. The population at A had declined by 80% since 1971, from 150 breeding individuals to 35. While equivalent historical data for the other sites were unavailable, landowners thought their populations had remained stable.
Genetic analyses detected differentiation between all four populations even though they were only separated by a maximum of 24 km. Differentiation at this small spatial scale is rare in birds, and probably reflects a combination of the highly sedentary nature of this species and the fragmentation of its breeding habitat.
Annual productivity of the declining population (A) did not differ between the pre-decline period (1967–1971) and the present. Similarly, productivity at the only stable population at which it was measured (B) and at A was comparable, as were post fledging survival rates.
Over-winter survival rate was much lower at A than at all other sites, however, with only 40% of birds surviving between one autumn and the following spring. To investigate the cause of this low survival, supplementary seed food was provided experimentally during the winter at all of the sites, yet increased over-winter survival only at A.
We concluded that population A was limited by over-winter food supply and that the restricted movement between populations may be insufficient to sustain it by immigration. Winter food supplies may have been diminished by reductions in spring sowing of cereals (loss of stubbles), herbicide-mediated reductions in weed seeds, and increases in bird-proof storage of grain and animal feed stocks.
The hypothesis that rural house sparrows may decline by a series of local extinctions was supported by a farmer survey. This revealed that house sparrow decline presents itself not as a reduction in numbers at all farms, but as a complete loss at some farms, with population stability at others.
As well as winter food supplies, invertebrate food for nestlings or lack of nest sites may be limiting at some sites. Given the house sparrow’s sedentary nature, these resources must be provided as ubiquitously as possible. The new ‘entry level’ agri-environment scheme, which is hoped to reach up to 80% of farms, may help to achieve this.