Contents of report
Breeding Bird Survey
Common Birds Census
Constant Effort Sites
Nest Record Scheme
Waterways Bird Survey
Alerts
Summary
What the categories mean
Return to BTO Home Page
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2. Methodology

2.2 Waterways Bird Survey

The Waterways Bird Survey (WBS) has monitored up to 20 riparian bird species on canals and rivers throughout the United Kingdom since 1974. As with the Common Birds Census (CBC), the territory-mapping method is used to estimate the breeding population of waterbirds on each plot and shows in detail each bird's habitat usage. The plots average 4.4 km in length; almost half are slow-flowing lowland rivers with the rest either fast-flowing rivers/streams or canals. There are currently around 120 plots distributed throughout the United Kingdom. Geographical spread is slightly different to that of the CBC because there is a higher proportion of plots in the north and west of England. Wales, Northern Ireland and Scotland are again rather poorly covered.

As with the CBC, all fieldwork is carried out by volunteers. Observers are asked to survey their plot on nine occasions between March and July, mapping all the birds seen or heard onto 1:10,000 scale maps. Registrations are then transferred to species maps, which are analysed to reveal the numbers and positions of territories for each species. In 1994 observers were asked to complete their own territory analysis, based on issued guidelines for the first time. This has successfully speeded up the processing of WBS data at BTO headquarters. The results are still checked by BTO staff, and observer's analyses have generally been found to be consistent with those of BTO analysts. Population indices are estimated using the methods described for the CBC (section 2.1), and an index series has been created for each species.

Population changes are reported annually in BTO News for 19 riparian species, five of which are not covered by the CBC, and many of the others are found in higher numbers in the WBS sample than in the CBC sample. Long-term trends were summarised in Population Trends in British Breeding Birds (Marchant et al. 1990) and in a recent issue of BTO News (Marchant & Beaven 2000). For those species covered by both CBC and WBS, there is generally much agreement between the population indices from the two schemes. However, there are one or two exceptions, such as for Lapwing, the populations of which declined rapidly on arable farmland during the late 1980s while numbers on WBS plots, typically representing populations along river flood plains, showed greater stability.

As the WBS employs very similar methods to the CBC, the validation studies carried out for the latter generally hold true for the WBS (see section 2.1). Marchant et al. (1990) found that there has been little change in the composition of the WBS sample in terms of habitat type or geographical spread. Data analysis follows the same methods as used for CBC (Section 2.1), except that the "Unrepresentative?" caveat has not been used.

2.1 Common Birds Census
2.2 Waterways Bird Survey
2.3 Breeding Bird Survey
2.4 Heronries Census
2.5 Constant Effort Sites Scheme
2.6 Nest Record Scheme
2.7 The Alert System

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The report should be cited as: Baillie, S.R., Crick, H.Q.P., Balmer, D.E., Bashford, R.I., Beaven, L.P., Freeman, S.N., Marchant, J.H., Noble, D.G., Raven, M.J., Siriwardena, G.M., Thewlis, R. and Wernham, C.V. (2001) Breeding Birds in the Wider Countryside: their conservation status 2000. BTO Research Report No. 252. BTO, Thetford. (http://www.bto.org/birdtrends)




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Last updated: 21 October, 2003

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