Scotland's Marine Atlas: Information for The National Marine Plan

WATERBIRDS

Scotland's coast is of particular importance for waterbirds and there are a number of sites of international importance for the wintering populations of wildfowl, waders and geese that they support. Some species of wader such as Eurasian oystercatcher ( Haematopus ostralegus), dunlin ( Calidris alpina alpina), common redshank ( Tringa tetanus), ruddy turnstone ( Arenaria interpres) and purple sandpiper ( Calidris maritima) are associated with coastal environments. Many species are long distance migrant visitors that breed in the high Arctic and winter on Scotland's coasts. Wildfowl such as common shelduck ( Tadorna tadorna) and Eurasian teal ( Anas crecca) occur in estuaries whilst species such as common eider ( Somateria mollissima) are found on more open coasts.

Overall waterbird numbers peaked at 120% in 1995/96 in relation to the 1975/76 baseline, since when there has been a gradual decline. The latest indicator for 2008/09 stands at 102%. Wader numbers which peaked at 102% in 1996/97 have shown an increasing rate of decline and are now standing at 70%, the lowest value since the early 1980s. Wildfowl (ducks and swans) numbers have dropped to 95%, the lowest since 1987/88. In contrast, geese numbers have increased significantly since the baseline was established in 1975/76 and are currently showing a 333% increase.

All waders except Eurasian oystercatcher, grey plover ( Pluvialis squatarola) and sanderling ( Calidris alba) have declined in numbers in recent years. There have been long-term declines in seven species, the largest have been seen in dunlin and northern lapwing ( Vanellus vanellus) numbers (-76%) and a further five species stand at below half of the baseline level (i.e. ringed plover ( Charadrius hiaticula), purple sandpiper, ruddy turnstone, common redshank and European golden plover ( Pluvialis apricaria)). The reasons for these declines are still to be fully explained but may be due to redistribution of wintering birds across north-west Europe due to climate change effects.

There is variation in the fortunes of different wildfowl species, eight species show an increase in numbers, with common shelduck and northern pintail ( Anas acuta) reaching their all time highs, whereas seven species have declined (i.e. tufted duck ( Aythya fuligula), greater scaup ( Aythya marila), northern shoveler ( Anas clypeata), mallard ( Anas platyrhynchos), common eider, red-breasted merganser ( Mergus serrator) and common pochard ( Aythya ferina)), the latter four reaching their all time lows.

Wintering waterbirds average WeBS Count (2004/05 to 2008/09)

Count data were obtained from the BTO Wetland Bird Survey.

Special Protection Areas for wintering waterbirds containing in excess of 10,000 birds ( counts are the 5 year peak winter mean).

1 The WeBS principal site boundaries may cover a larger area than the SPA site boundary. Full details of SPA site counts are available from BTO and site alerts can be downloaded from http://www.bto.org/volunteer-surveys/webs/webs-alerts-spas

Wintering Waterbird Indicator

Abundance of wintering waterbirds in Scotland, 1975/76 - 2008/09

Source: Wetland Bird Survey Results ( WeBS)

Coastal Special Protection Areas supporting waterbirds that use the intertidal and sea areas (some sites also support various goose species (*) which are listed for completeness but which tend only to use adjacent coastal habitat for roosting; sites that only support goose species are not included)

Pressures

Waterbirds face a range of pressures including various climate change related factors such as temperature changes, salinity changes and sea-level rise. There are already indications that these are resulting in changes in the distribution of certain species with a general north-eastwards shift.

Contamination by hazardous substances also poses a threat. Seaduck, divers and grebes are particularly vulnerable to oil pollution and even a relatively small spill can have a significant impact if it occurs in a particularly important area for a given species. The reduction in the enrichment of many estuarine mudflats, in particular as a result of better regulation of sewage discharges and nutrient runoff, has resulted in a decline in the abundance of some species as the productivity of the mudflats has declined.

The removal of prey species either directly through fisheries or incidentally through disturbance to the seabed can result in reduced availability of food for various waterbird species. Habitat damage and loss due to a variety of coastal activities such as coastal defences, land claim, construction of marinas etc. can also have serious impacts on waterbird numbers.