Scotland’s waterbird numbers have slumped to the lowest level since monitoring began in the 1970s, with waders showing the greatest decrease.
National agency NatureScot has published its latest biodiversity indicator, which tracks populations of 41 species using data gathered by volunteers through the BTO/RSPB/ JNCC Wetland Bird Survey (WeBS).
The overall number of waterbirds was seven per cent lower in 2018/19 than when comprehensive counting started in 1975. There were also large variations between species. Waders – including the oystercatcher, lapwing, golden plover, knot and dunlin – declined by 58%. But wintering numbers for two species – the black-tailed godwit and grey plover – increased, while numbers of sanderling remained stable.
Climate change is causing some species to shift their wintering distributions. This may account for some of the declines as birds select areas with more favourable foraging conditions.
For waders that winter along rocky shores, among them purple sandpiper and turnstone, the reasons for the decrease are not well understood. Some studies suggest that poor breeding success in their Arctic coastal and tundra breeding grounds could be a factor.
Simon Foster, NatureScot’s trends and indicator analyst, said: “Wader numbers peaked around 1997/98 but since then have been in steady decline.
“Scotland is in an important position within the East Atlantic Flyway, which is the migration route used by our waders, so these data are invaluable in piecing together what is happening globally.
“By sharing research and working with others across the entire flyway we can better understand the global forces at play, especially climate change.
“Collaboration is vital to finding solutions to the declines of waders. Improving coastal habitats, such as through coastal realignment, helps Scotland’s waterbirds, providing areas for feeding and roosting waterbirds, as well as helping with climate resilience.
“For wintering waders which also breed in Scotland, such as curlew, golden plover and oystercatcher, we are also supporting schemes such as The Working for Waders initiative, which is taking active steps to reverse the decline in our wading birds through a range of targeted projects.”
Dr Ben Darvill, from BTO Scotland, added: “It’s thanks to the network of dedicated WeBS volunteers throughout Scotland that we are able to produce these trends. They go out once a month to monitor the waterbird numbers at local sites, and their collective efforts are hugely valuable –our thanks go out to all of them.”
The latest results show that numbers of wildfowl species such as whooper swan, teal, goldeneye and goosander increased by 21%.
However, four species of wildfowl – mallard, pochard, scaup and eider – as well as cormorant and coot, have declined.
Experts pointed out that many wildfowl are migratory and some species’ trends may reflect shifting wintering areas. For example, populations of wigeon and teal are increasing in Scotland, with more birds opting to winter around our coasts. In contrast, wintering pochard numbers have dropped markedly as a result of factors including changes in water quality and invasive species.
Barnacle geese have seen some of the largest increases, while Greenland white-fronted geese have declined since the late 1990s.