The assessment of national Alerts aims to focus attention on species declining countrywide. It is intended that this should be used as a basis for directing research and subsequent conservation efforts if appropriate. It may not always be possible to address the causes of these declines, for example, if it were to be determined that a particular trend is being driven by climate change or pressures on bird populations on their breeding grounds or staging posts outside the United Kingdom. However, national trends can provide useful information towards our understanding of change at the site level.

The proportion of species for which Alerts were triggered in each of the constituent countries of the United Kingdom is shown in Figure 5.1. In Great Britain as a whole, High-Alerts have been triggered for two species of the 39 evaluated, and Medium-Alerts for a further 5 species. Although this would imply a relatively favourable situation, it represents a slightly worsening plight for waterbirds. In 2003, for example, no High-Alerts were triggered for any waterbird species (Austin et al. 2003). Furthermore, whilst the situation in England and Scotland remains fairly favourable, the numbers of a wide range of species are declining in Wales and Northern Ireland. In Northern Ireland, the majority of declining species are diving ducks, and the downward trend has in most instances been driven by large decreases in numbers at Lough Neagh and Lough Beg SPA. In Wales, many of the declining species are waders, and this may represent a global redistribution of the United Kingdom population north-eastward in response to climate-change (Austin and Rehfisch 2005; Maclean et al., submitted).

To date, the Alerts status of waterbirds has been assessed for 77 SPAs and a further 26 SSSIs. The WeBS Alerts system does not aim to explain the causes of underlying declines on particular sites, but rather focuses attention on those sites or those species on a particular site giving particular cause for concern. When Alerts have been triggered it is intended that this should provide a basis on which to direct hypothesis driven research.

The stacked histograms below (Figure 5.3) summarise the number of Alerts triggered for each of the sites reported in relation to the total number of species assessed for each site. It is intended that this figure will enable attention to be focused on those sites that give particular cause for concern. It is suggested that several sites be flagged for priority attention. Trends on Abberton Reservoir, Belfast Lough, Lough Neagh and Lough Beg, and the Stour and Orwell Estuary, give the greatest cause for concern, as all these site have a high number of waterbird species that are designated features of the site and a high-proportion of species for which Alerts have been triggered.

The decline in Pintail on the Mersey Estuary is also noteworthy. This site, once the most important in the United Kingdom for thus species hosted peaks exceeding 10,000 birds throughout most of the 1980s and as high as 18,450 in the winter of 1980/81. Recently numbers have declined to around 200 birds in the winters of 2003/04 and 2004/05 (Banks et al. 2006).