Scotland’s coasts and inland waters are of particular significance for wintering waterbirds, hosting substantial numbers of waders and wildfowl. In an international context Scotland’s extensive rocky shorelines are important for specialist species such as purple sandpiper and turnstone, and its islands and agricultural lowlands for migratory geese. There are more than 50 sites of international importance for wildfowl and wader species. Many are long distance migrants, breeding in the high Arctic and wintering in Scotland.
Monitoring Scotland's wintering waterbirds
Each month throughout the winter, volunteers count waterbirds around Scotland’s estuaries, rocky shorelines and inland waterways. These counts are mostly undertaken through the Wetland Bird Survey (WeBS), with additional targeted counts for geese and swans, and periodic surveys of rocky shore waders. WeBS is a partnership jointly funded by the BTO, RSPB and JNCC, in association with WWT, with fieldwork conducted by volunteers. The results are used by NatureScot, other Government agencies and environmental NGOs to provide population estimates, determine trends in numbers and distribution, and identify important sites for waterbirds. Since 1975, trends in 41 species of waterbirds (used here to include wildfowl, waders, cormorant, grebes and coot) occurring in Scotland have been monitored.
Since counts began in the winter of 1975/76:
- Overall waterbird numbers (41 species/populations) decreased by 10%.
- Goose numbers (7 species/populations) increased by 263%.
- Ducks and swans (wildfowl) numbers (16 species) increased by 3%.
- Wader numbers (14 species) have declined to 55% lower than in 1975/76.
Overall waterbird numbers (the combined trend for all 41 species/populations) have decreased by 10%. The individual species trends reveal a range of fortunes for Scotland’s wintering waterbirds. Most waterbirds can be highly mobile and research has shown that some are shifting their distributions in response to environmental change (Pavón‐Jordán et al, 2019).
Wader numbers peaked around 1997/98. Since then the combined trend for waders has shown a steady decline; from 2012 the trend has stabilised around 50% lower than the baseline. Scotland is in an important position within the East Atlantic Flyway (the migration route used by our waders) and the declines for many of the species have occurred across the flyway.
Eleven species declined (oystercatcher, lapwing, golden plover, ringed plover, curlew, bar-tailed godwit, turnstone, knot, dunlin, purple sandpiper and redshank). Their trends show a similar pattern, peaking between 1994/95 to 1998/99 then declining from 2002/03. Two species have increased, black-tailed godwit and grey plover. Wintering numbers of sanderling remained stable.
Reasons for the changes
Most of our wintering waders are migratory, and many use the Arctic as their main breeding area. A recent review on the trends of Arctic birds by Smith et al. 2020 highlighted the scale of the declines for Arctic waders. Whilst studies looking into the drivers of change are limited across the Arctic, there is evidence that quality of stopover sites used to refuel during migration, climate change and mismatches in insect availability during the breeding season are contributing to declines. Climate change may be allowing some species to shift their distributions; this may account for some of the declines as birds select wintering areas that are more favourable. However, we lack key knowledge on whether this is actually happening or whether the declines are at the population scale. Climate change effects may result in a northward shift in their Arctic breeding ranges and may be leading to them not being able to find food during the breeding season (climate mismatch). For species where we do have knowledge, such as knot and dunlin, studies have shown that populations can be highly mobile. When there are milder winters across Europe this enables birds to remain on continental wintering sites. For other waders, in particular rocky shore waders such as purple sandpiper and turnstone, the reasons for declines are not well understood. Some studies suggest that poor breeding success is leading to the declines. Collaborative monitoring (across the entire flyway) is essential to help understand and reverse the declines of waders.
For our wintering waders which also breed in Scotland such as curlew, golden plover and oystercatcher, targeted land management has been shown to help. The Working for Waders initiative is taking active steps to reverse the decline in wading birds in Scotland through a range of targeted projects.
Ducks and swans
Duck and swan numbers have remained relatively stable, peaking around 1993/94. Within the trend, there is marked variation. Ten species have increased (Mute swan; whooper swan; shelduck; shoveler; gadwall; wigeon; pintail; teal; goldeneye; and goosander). Four have declined (mallard; pochard; scaup; and eider). Two were stable (tufted duck and red-breasted merganser).
Reasons for the changes
Many of our wildfowl are migratory, with some species such as wigeon and teal undertaking long distance migrations to breeding grounds in Arctic Russia. Trends at a country level may reflect shifting wintering distributions. . For example, wigeon and teal are increasing in Scotland with more birds opting to winter around our coasts in preference to moving to other wintering areas. A new study (Project Penelope) focussing on wigeon aims to shed light on the migration of Eurasian Wigeon and learn more about how they use the European Protected Sites (EPS) network, and the wider landscape. This project will provide invaluable information on wigeon habitat use, movements and demography (including reproduction and survival), which will be immediately useful to assess the adequacy of our protected sites network and inform decisions to secure the sustainability of hunting. Pochard and scaup showed the largest declines (93% and 89% respectively). Climate change may be affecting the distribution of scaup. A recent study (Marchowski, 2020), analysing 30 years of count data for scaup, revealed a shift in the distribution of the species within its wintering grounds towards the east and north, highlighting the need for international collaboration to understand changes in species numbers across their range.
Other waterbirds (included in the overall waterbird indicator)
Four species of wildfowl are included in the main waterbird category and do not contribute to the other categories. One increased (little grebe) and the rest showed declines (great-crested grebe; cormorant; and coot). For the declining species, the drivers of change for these are not known.
The Goose indicator shows more than a three and a half fold steady increase since 1975/76, peaking in 2016/17 at 286%, but recently it has been falling slightly to 263%. All five geese species (seven different races/populations) have increased over the past 45 years, particularly native Greylag Goose, Pink-footed Goose and both races of Barnacle Goose. Barnacle geese have seen some of the largest increases, with protective legislation and changes in agricultural management helping to improve their fortunes to the degree that management options are now being explored to help reduce emerging conflicts with crop-growers (McKenzie, 2014). The Taiga race of Bean Goose has declined slightly over recent winters. In 2015 an International Single Species Action Plan was published for Taiga bean geese. Elsewhere in their range populations are declining due to hunting and disturbance. Taiga bean geese have been protected in Scotland since 1981 and the small population that winters in Scotland is monitored annually. Greenland White-fronted Geese have shown a moderate decline since highest numbers in the late 1990s. Note that introduced (non-native) geese are not included in these calculations, nor rare wintering species in Scotland.
The Wetland Bird Survey operates throughout Scotland. Although most major waterbodies and estuaries are covered by volunteers, there is always a need for new counters. Counts from areas not well monitored (such as North West Scotland and smaller inland waterbodies) are welcome as well. To become a WeBS volunteer contact BTO.
The Wetland Bird Survey (WeBS) monitors wintering waterbirds covering all of the major estuaries throughout the UK. The Wetland Bird Survey (WeBS) is a partnership jointly funded by BTO, RSPB and JNCC, in association with WWT, with fieldwork conducted by volunteers. This is complemented by annual results of the WWT/JNCC/NatureScot Goose and Swan Monitoring Programme and Non-Estuarine Waterbird Surveys undertaken periodically to improve coverage of the coastline outside estuaries. Further information on waterbird trends on protected sites in Scotland can be found online through WeBS Alerts.
McKenzie, R. (Ed.) 2014. Islay Sustainable Goose Management Strategy. NatureScot.
Marchowski, D., Ławicki, Ł., Fox, A.D. et al. 2020. Effectiveness of the European Natura 2000 network to sustain a specialist wintering waterbird population in the face of climate change. Sci Rep 10, 20286.
Pavón‐Jordán D, Clausen P, Dagys M, et al. 2019. Habitat‐and species‐mediated short‐and long‐term distributional changes in waterbird abundance linked to variation in European winter weather. Diversity and Distributions. 25(2), 225-39.
Smith, P.A., McKinnon, L., Meltofte, H. et al. 2020. Status and trends of tundra birds across the circumpolar Arctic. Ambio 49, 732–748