Waterbirds that have historically migrated to the UK during winter have stopped doing so because of global warming, a new survey reveals.
Many species of duck and swan arrive on British shores as winter arrives because temperatures here are balmier than where they are coming from.
But with many northern regions, such as Scandinavia, getting warmer in autumn and winter than ever before in recorded history, many birds are choosing to stay put.
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The report revealed numbers of Scaup (pictured) - a type of diving duck - arriving on British shores have dropped by three-quarters since 1973
The latest Wetland Bird Survey Report (WeBS) published today by the British Trust for Ornithology (BTO) reveals current numbers of birds in the UK.
But data from the survey shows that the winter holidays of many migratory species have fallen out of fashion.
The report revealed numbers of Scaup - a type of diving duck - arriving on British shores have dropped by three-quarters since 1973.
Goldeneye and Bewick's Swans are also remaining on the other side of the North Sea in increasing numbers during the winter months, the figures show.
The number of these birds seen in the UK dropped by 58 per cent and 88 per cent, respectively, between the winters of 1993/94 and 2018/19.
Coot numbers have also fallen by 15 per cent over the same period.
In Northern Ireland, Scaup sightings have fallen by 60 per cent between 1993 and 2019, although Lough Neagh remains the wintering stronghold in the UK.
Goldeneye and Bewick's Swans (pictured) are also remaining on the other side of the North Sea in increasing numbers during the winter months, the figures show. The number of these birds seen in the UK dropped by 58 per cent and 88 per cent, respectively, between the winters of 1993/94 and 2018/19
Following a sharp decline in the late 1970s - linked to a decline in the amount of waste grain from whisky distilleries ending up in river estuaries - Scotland has seen its overwintering Scaup numbers further fall by just over a fifth (22 per cent) between 1993 and 2019.
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Goldeneye and Coot both fell by 38 per cent in Scotland over the same period whereas, in Wales, Scaups fell by 77 per cent, Goldeneye by 43 per cent, and its wintering population of Bewick's Swans fell by 90 per cent.
Simon Wotton, senior conservation scientist at the Royal Society for the Protection of Birds (RSPB), said: 'Whilst the decline of some wintering waterbirds here in the UK means certain species are not migrating as far, there is concern over where they are now spending most of their time.
'Wetlands across Europe are vital for millions of waterbirds every year and provide them with a much-needed home through winter, but not all are created equal.
'Many of Europe's wetlands have been drained, exploited and some are without protection altogether.
'Ensuring these areas are designated and protected appropriately will become even more critical in safeguarding the ongoing survival of many of our migrating waterbirds.'
Teresa Frost, WeBS Manager at the BTO, said 'The big drop in Scaup in Scotland in the 1970s was linked to a reduction of waste grain from whisky distilleries ending up in estuaries.
'But the continued decline since then is driven by milder winters in the Baltic Sea - and that's affecting lots of species.
'We are fortunate to still have many hundreds of thousands of waterbirds visiting the UK in winter, even if the numbers are not quite what they used to be for some species, and we are grateful to the many volunteers who count them for us and make it possible to understand what's changing.'