Abstract from BTO Research Report No 376:

Newson, S.E., Crowe, O. & Noble, D.G. (Aug 2005)

Scoping study on Integrating Countryside Bird Survey and Breeding Bird Survey Data to Generate All-Ireland Trends

Executive Summary

1. Breeding bird populations are used as indicators of sustainability throughout many parts of Europe. In the UK and Republic of Ireland, breeding bird populations have been monitored using line transect methodology since 1994 and 1998 respectively. The first collaborative analyses of breeding bird populations across the entire island of Ireland was initiated in January 2004. The project is funded the Environment and Heritage Service in Northern Ireland, and carried out by the two key organisations responsible for the coordination of the respective schemes in Britain and Ireland, the British Trust for Ornithology and BirdWatch Ireland.

2. Data were compiled for all species recorded between 1998 and 2003, in Northern Ireland and the Republic of Ireland (the latter subdivided into three regions – east, south and west).

3. Two similar log-linear regression modelling approaches, using the SAS procedure GENMOD and the computer program TRIM were used to produce trends in relative abundance in the UK and Republic of Ireland respectively. An assessment is made to ensure that these techniques produced similar results. Thereafter analyses for all-Ireland and Northern Ireland were produced using SAS, while those for the Republic of Ireland and regions were produced using TRIM. Trends were produced for all species that were present in at least 30 1-km squares.

4. A total of 151 species were recorded across the island, including 142 species in the Republic of Ireland and 125 in Northern Ireland. Wren, Robin and Blackbird were the most widespread, while Rook, Starling, Wren and Blackbird were the most abundant.

5. In total, trends were produced at an all-Ireland level for 61 species, for 55 species in the Republic and for 28 species in Northern Ireland. These included 27 species of conservation concern in the UK and 13 species of conservation concern in Ireland. Twelve species exhibited significant changes in abundance between 1998 and 2003. Trends were produced For 26 species, it was possible to produce trends for all four regions (NI and three regions in the Republic of Ireland). Increases in Pheasant, Woodpigeon and Wren and declines in Skylark, Swallow and Robin were consistent across regions, but trends for Mistle Thrush and Coal Tit varied between regions.

6. An assessment was made to examine the implications of a hypothetical cessation in professional coverage, and, conversely of an expansion in survey effort. Loss of professional coverage across Ireland could prevent the production of trends for eight species.

7. While an increase in survey coverage (overall or targeted to particular regions) is not predicted to substantially increase the number of species for which trends can be routinely reported, increasing sample size is likely to substantially increase the power to detect population changes, and the number of significant increases or declines that could be reported.

8. Production of all-Ireland population trends should be continued on an annual basis, and reported in a variety of media. Improved coverage, particularly around the border regions may result from workshops and meetings carried out at regular intervals. It is recommended that there be increased liaison between BBS and CBS coordinators.

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