Report 374
The numbers of inshore waterbirds using the Greater Thames during the non-breeding season; an assessment of the area's potential for qualification as a marine SPA
(2009)
Webb, A., Dean, B.J., O'Brien, S.H., Sohle, I., McSorley, C., Reid, J.B Cranswick, P.A, Smith L.E & Hall. C
In 1979, the European Commission adopted the European Council (EC) Directive on the conservation of wild birds (commonly known as the ‘Birds Directive’) in response to the 1979 Bern Convention on the conservation of European habitats and species (the ‘Bern Convention’). The Birds Directive addresses ‘the conservation of all species of naturally occurring birds in the wild state in the European territory of the Member States to which the treaty applies’ (79/409/EEC). It requires Member States to identify and classify in particular the most suitable territories in number and size as special protection areas (termed Special Protection Areas or SPAs by Member States) for the conservation of rare and vulnerable species listed on Annex I of the Directive, as well as regularly occurring migratory species.

Summary

 
 
 

Aerial surveys of the Greater Thames were carried out over a total of 58 days over eight winter seasons between 1988/89 – 2006/07. These consisted of three strip transect aerial surveys (1988/89, 1989/90) and 20 line transect aerial surveys (2001/02-2006/07) conducted by Joint Nature Conservation Committee, Wildfowl & Wetlands Trust and the Natural Environmental Research Institute, Denmark.

 

The species recorded were: common eider Somateria mollissima, common scoter Melanitta nigra, velvet scoter Melanitta fusca, red-breasted merganser Mergus serrator, red-throated diver Gavia stellata, great northern diver G. immer, black-throated diver G. arctica, great crested grebe Podiceps cristatus and little gull Larus minutus. The first part of this report describes analyses of these data to determine the numbers of birds present for each species. The second part of this report assesses those numbers against the appropriate guideline thresholds, to determine whether the area, or part of it, might meet the site selection requirements under Stage 1 of the UK Site Selection Guidelines as a Special Protection Area (SPA) under the European Union Birds Directive.

 

The mean of peak estimates of red-throated diver numbers was 6,618 individuals for the inshore areas of the Greater Thames. Peak estimated numbers of red-throated divers exceeded the appropriate Stage 1 threshold (170 individuals) under the UK SPA site selection guidelines in all five out of the five most recent winter seasons.

 

The mean of peak estimates of little gull numbers was 115 for the inshore areas of the Greater Thames. Peak estimated numbers of little gull exceeded the appropriate Stage 1 threshold (50 individuals) under the UK SPA site selection guidelines in only two out of the five most recent winter seasons. Further surveys are required to determine if this species should be a qualifying feature of any future SPA in the area, as earlier surveys most likely under recorded little gulls. For common eider, common scoter, velvet scoter, red-breasted merganser, great northern diver, black-throated diver and great crested grebe, peak estimated numbers in the Greater Thames area did not exceed the appropriate Stage 1 threshold under the UK SPA site selection guidelines in any season. Nor did the mean of peak estimates across all surveys exceed qualifying thresholds for these species.

 

Based on the available data, an estimated 8,355 individual inshore waterbirds regularly use the inshore waters of the Greater Thames during the non-breeding season. This estimate does not exceed the appropriate Stage 1 threshold (20,000 individuals) for an assemblage of nonbreeding waterbirds under the UK SPA site selection guidelines.

 
 
ISSN 0963 8901
 
Please cite as: Webb, A., Dean, B.J., O'Brien, S.H., Sohle, I., McSorley, C., Reid, J.B Cranswick, P.A, Smith L.E & Hall. C, (2009), The numbers of inshore waterbirds using the Greater Thames during the non-breeding season; an assessment of the area's potential for qualification as a marine SPA, JNCC Report 374, ISSN 0963 8901