Some of the most popular songbirds in the U.K. are being sighted much less frequently, the Royal Society for the Protection of Birds said yesterday. A survey carried out by the group’s members found that the numbers of starlings and house sparrows have halved in the last 10 years. The group blamed the problem on the advance of big-time farms. Mike Everett, a RSPB spokesperson, said pesticides were reducing the birds’ food supply and farming was also destroying wild spaces and the birds’ hedgerow habitat.