Swedish farmland bird populations have declined for decades, reflecting trends throughout northern Europe. These declines have been attributed to agricultural intensification, resulting in loss of ecological heterogeneity at multiple spatial scales. The house sparrow is a farmland bird that has declined with ca 50% in Sweden. The house sparrow depends on insects for breeding and seeds for survival. Increased use of pesticides, more competitive crops and reduced availability of field borders may have resulted in loss of weeds and thereby availability of both insects and seeds. Reduced animal husbandry may have reduced availability of insects. In particular, we suggest that farm specialisation has resulted in increased spatial separation of resources needed for successful reproduction and over winter survival and that this may be the main cause behind the population decline of the house sparrow.
The aim of this study of house sparrows is to: