Thirteen breeding seasons have now passed since the British Trust for Ornithology started its very successful Common Birds Census. The main aim of the scheme has been to keep an annual check on the population levels of our more common birds. The technique involves mapping the breeding territories of birds on study areas selected by birdwatchers throughout the country. An important secondary object has been to quantify the breeding bird communities in different habitats and areas. Farmland is the chief habitat censused, others ranging from woodland, park, heath and moor to gravel pit, sewage farm and nature reserve. New plots are always welcomed, particularly farmland. Details may be obtained from Kenneth Williamson, Populations Section, BTO, Beech Grove, Tring, Hertfordshire HP23 5NR.