Wildlife Recording Guidelines
Breeding Bird Surveys

Two generic breeding bird survey techniques are commonly used. The Common Birds Census (CBC), first used in the 1960’s is the most popular breeding bird survey used. The second method is the Breeding Bird Survey (BBS). The CBC is run by the BTO, but anyone can follow the methodology for the surveys. CBC is best suited for woodland plots of between 10 and 20 ha and farmland plots between 50 and 100 ha. Each visit should take around 3 to 4 hours.

Common Bird Census Methodology

The survey site is visited ten times between March and July, with visits ideally at ten-day intervals. Visits should be made in the early morning and be timed to coincide with peak times of song / breeding activity. On some sites a couple of evening visits are recommended for nocturnal species such as nightjar, woodcock and owl species. Surveys should not be undertaken in strong wind and rain should be avoided if possible.

Map the boundary of the survey site at a scale of approximately 1:2,500. You will require about a dozen copies of the map - one for each visit and a couple of spares. Walk the survey area at a constant steady pace and choose a route that takes you within 50 metres of every point within the survey boundary. Mark down all breeding registrations on the visit maps along with details of date, weather and visit number. Standard codes are available for all UK breeding species and different symbols are used for different breeding registrations such as singing, alarm calls, adults carrying food etc.

Upon the completion of the ten visits all the visit information is transcribed on to species maps. Ideally a single map should be used for each species, although it is possible to double-up some species where their breeding territories do not overlap. Once the information is transferred to species maps, then clusters of registrations will reveal approximate territories. Actual determination of territories can be open to interpretation, but generally a cluster of registrations will centre on singing males and or nest activity.

Breeding Bird Survey Methodology

The RSPB, BTO and JNCC established the BBS as an annual survey of widespread and abundant terrestrial species in the UK.

This survey is a sample technique and does not require the total survey area to be walked; rather a walk of two 1-km transects selected within randomly allocated 1-km squares. It is therefore better suited for large tracts of land.

Analysis of the collected data is best undertaken by a specialist statistician; ideally the specialist DISTANCE software be used to calculate densities and population sizes.

The survey should be commenced between 0600 and 0700 hrs and no later than 0900 hrs. Three visits are made per transect, one in April to establish the transect route and map the habitats present. The second visits should be in May and June and be four weeks apart. These latter two visits are used to collect the survey data. On each visit the first transect is walked slowly and all birds seen along the route recorded per 200 metres length of the transect. Their relative distance from the transect (within 25 metres of the line, 25 to 50 metres of the transect, over 100 metres from the transect line and those flying over) should also be noted.

Further details of both methods, together with details of species specific monitoring methods are contained in Gilbert, Gibbons and Evans (1998) and on the BTO Web Site http://www.bto.org/survey

References

Buckland ST, Anderson DR, Burnham KP and Laake JL (1993) Distance Sampling: Estimating Abundance of Biological Populations Chapman and Hall. London

Gilbert G, Gibbons DW and Evans J (1998) Bird Monitoring Methods. RSPB Sandy

Gregory RD, Bashford RI, Balmer DE, Marchant JH, Wilson AM and Baille SR (1996) The Breeding Birds Survey 1994-1995. BTO Thetford

Gregory RD, Bashford RI, Balmer DE, Marchant JH, Wilson AM and Baille SR (1997) The Breeding Birds Survey 1995-1996. BTO Thetford

Marchant JH (1983) BTO Common Birds Census Instructions BTO Thetford

Marchant JH, Hudson R, Carter SP and Whittington P (1990) Population Trends in British Breeding Birds BTO Thetford