Wildfowl on the wane as winters become milder

Fewer ducks, geese, swans and wader species are travelling to the UK in winter as milder conditions continue to define the season across northern Europe, according to a newly published report.

The UK is host to internationally important numbers of wintering waterbirds, and the long-standing Wetland Bird Survey (WeBS) and Goose and Swan Monitoring Programme (GSMP) provide essential data that inform decision makers when considering conservation measures for these birds.

But the BTO's Waterbirds in the UK 2022/23 report shows that many species are altering their behaviours in response to warmer winters.

The UK's wintering population of Common Goldeneye has halved in the last 25 years (Steve Cribbin).

 

Winter refuge

Historically, harsh conditions in northern and eastern Europe would see huge numbers of birds migrating to the UK to make the most of the relatively weather experienced here. But as the climate warms, previously frozen landscapes become increasingly accessible in the winter months and significant numbers of birds are now staying closer to their breeding grounds. This is a phenomenon known as short-stopping.

Those that do still make the journey across the North Sea to spend the winter in the UK are often arriving later and leaving earlier, therefore staying here for much shorter periods. This has become increasingly noticeable in such species as Bewick's Swan, which has declined by 96% in the last 25 years, while Common Goldeneye numbers have halved and Dunlin have dropped by a third.

Although 2022 and 2023 were the two warmest years on record in the UK, the 2022-23 winter was something of a mixed bag. A notable cold snap ensued in December 2022, but this was followed by a period of milder weather before temperatures tumbled briefly in mid-January. The late winter period otherwise remained mostly mild and settled.

As a consequence, there appeared to be little major cold weather-related movement of wildfowl and waders – once again many species remained on the continent.

The survey also revealed that other familiar waterbirds such as Eurasian Coot are being affected by milder winters. The UK coot population comprises both residents which breed here and continental birds which join them for the winter. While research suggests that there has been a decline in our breeding population, there has also been a notable reduction in wintering birds.

Bewick's Swan has declined by an incredible 96% in Britain since the 1990s (Jon Mercer).

 

Some species increasing

Not only has there been a reduction in birds arriving for the winter, but some birds that would previously have left the UK in autumn for warmer climes are now staying to overwinter. There has been an rise in such species as Black-tailed Godwit, which is increasingly remaining on our shores as opposed to migrating to southern Europe.

Dr Teresa Frost, WeBS Manager at the BTO, said: "The cold snaps during the winter forced ducks like Mallard to congregate on large wetlands covered by the survey. While it's fascinating to see short-term weather impacts like this in the data, the bigger story is research showing migratory short-stopping has contributed to the declines we are seeing in the survey for at least 25 of our commonest waterbird species that winter in the UK."

Simon Wotton, Senior Conservation Scientist at the RSPB, added: "The Wetland Bird Survey alongside the Goose and Swan Monitoring Programme is an invaluable tool for better understanding the impact of climate change on our wintering waterbirds that typically breed further north and east. The scientific community owe a debt of gratitude to the volunteers whose co-ordinated efforts make these long-term studies possible."

With data provided by more than 3,800 dedicated volunteers across the UK, the WeBS and GSMP deliver an annual assessment of ducks, geese, swans, waders and other waterbirds residing on, or passing through, our coasts, estuaries, lakes, reservoirs and rivers. The latest report can be read online.