Common Bird Census (CBC) survey

In order to estimate the number and distribution of each species present during the breeding season a territory-mapping approach is employed. The survey method used is based upon The British Trust for Ornithology's Common Bird Census (CBC) methodology (Marchant 1983). The site is visited at intervals of approximately ten days (in suitable conditions i.e. not in strong wind or heavy rain) between mid-March and mid-July. Visits are made in the early morning and timed to coincide with peak times of song / breeding activity. Evening visits may also be conducted to specifically target any species that are more active at this time (e.g. nightjar).

During each visit all bird registrations are marked on maps using BTO standard codes and activity symbols such as alarm calls, singing or carrying food.

The collected data from all the completed surveys is then transferred to species maps where they are analysed and likely territories identified. Actual determination of territories can be open to interpretation, but generally a cluster of registrations will centre on singing males and or nest activity.

Common Bird Census mapping remains the most accurate, practical way to determine the numbers and distribution of breeding birds within a study site. Our team of dedicated ornithologists regularly undertake CBC surveys in a variety of habitat types.