Birds breeding in British gardens: an underestimated population?

Capsule More birds breed in gardens than previous estimates suggest. Aims To determine the numbers of birds nesting on or in houses and gardens in Great Britain. Methods A questionnaire survey of 12 687 households in Great Britain was conducted in 2000, of which 6035 responded. A follow-up survey, to which 1757 responded, showed that people with no nests on their properties had been less likely to respond in the initial survey than had those with nests; it allowed this bias to be corrected. Sampling intensity differed regionally and by house-type (detached, semidetached, terraced); national population estimates were corrected to allow for this. The analysis was restricted to the 17 species that nested most frequently in domestic properties and to four others. Results It is likely that our estimates were somewhat too high for ten of the species. Even allowing for this, it is clear that the number of birds nesting in built-up areas is substantially higher than previously estimated for 13 of the 2 1 species. For some of these species, this has led in the past to significant underestimation of the total British population. Conclusions For some of the commonest British birds, accurate estimates of national populations are only possible if we get better estimates of numbers nesting in built-up areas than we have had in the past.