With their striking plumage, distinctive waddle and comical behaviour, they are known as the “clowns of the sky” – but the plight of Britain’s beloved puffins is no laughing matter.

A new report has warned that, if global warming is not checked, their numbers in the UK could plunge by nearly 90 per cent over the next three decades. Researchers also say decisions made at the COP26 climate summit in Glasgow will be crucial to preserving the species for future generations.

The puffin population has shrunk here and across Europe in recent years, leading to the bird being declared vulnerable to global extinction. Experts have said the phenomenon of warming seas – which affects food sources – is likely to be one of the main threats.

Now a report from the British Trust for Ornithology (BTO) indicates the UK population is projected to drop by a further 89% within just 30 years. Professor Juliet Vickery, the BTO’s chief executive, said: “This could represent a loss of over a million birds.

“There is a very real chance that our grandchildren may never know what it is like to see a puffin in Britain and Ireland.”

Scotland is home to more than 80% of the British and Irish puffin population, with colonies north of the Border including the Isle of May, Fair Isle, Lunga, and Noss National Nature Reserve.

READ MORE: Plea to help secure future of Scotland's puffins

The life of a young puffin hinges on whether its parents return with enough food, meaning an abundant supply of large, nutritious fish such as sandeels, sprats and herrings is vital. But increasing temperatures are having a negative impact on sandeel numbers in British waters, resulting in a hit to the breeding productivity of the puffins themselves.

The BTO report, which is called Climate Change And The UK’s Birds, states: “As with many seabirds, puffin breeding success is strongly linked to the availability of small fish such as sandeels, whose abundance is reduced by warming.

“Warming may also reduce puffin survival rates, particularly at southern colonies. As a result, the puffin is regarded as highly vulnerable to the effects of warming, with a mean 89% reduction in puffin populations across Britain and Ireland projected by 2050 under a high climate-change scenario.

“Given the UK supports 10% of the world puffin population, this is of international relevance. Habitat management at colonies to maintain open swards for nesting, and the control of non-native mammalian predators, may help compensate for negative impacts of climate change.”

The BTO report also states that, of the 20 breeding seabird species dependent on the marine environment as their primary foraging habitat, 11 are regarded as highly vulnerable to future climate change.

Professor Vickery said: “If we are to hold onto our important bird populations then we need governments to make the right decisions for nature and the climate at COP26, and to invest in real action towards meeting these commitments. We will also need to continue to monitor the results of our actions – to evaluate what works and what doesn’t.”

READ MORE: Puffins on the front-line of climate change and overfishing

Dr James Pearce-Higgins, director of science at the BTO and author of the report, said: “This new analysis reveals that, overall, one in five UK bird species will be affected by climate change. It is not just our seabirds that will be impacted – we will lose some of our best-loved summer visitors too. Once-familiar migrants, such as cuckoo and spotted flycatcher, have already seen their breeding populations more than halved during the last 25 years.”

He added: “Changing conditions here in the UK may have some impact, but the effects of changing weather patterns on the wintering grounds in Africa and along the migration routes used by these migrant birds may also be important.

“Projecting the future fortunes of these and other migrant birds is challenging, given their complicated lives that cross continents. Securing their future will require international collaboration right along their flyway.”

Puffins are undoubtedly among Scotland’s most distinctive seabird species. They have predominantly black, or black and white, plumage, as well as a stocky build and large beaks that become brightly coloured during the breeding season. The birds typically shed the outer part of their bill following the breeding season, leaving it looking smaller and duller.