IN THE darkness of their burrows, the puffin chicks starve to death while food lies decomposing in front of them.
They are not able to swallow the snake pipefish brought back from the North Sea by their parents because it is covered in a hard exo-skeleton.
With no fat on their bodies, the pufflings soon perish. Shunned even by predators, they are left to decay atop the cliffs of St Kilda - the latest victims of climate change.
As an iconic symbol of Scotland's wildlife, the Atlantic puffin is a bird cherished by nature enthusiasts.
But the long-term sustainability of the puffin population in one of the most internationally important breeding colonies is uncertain - St Kilda's clowns of the sea are starving to death. The National Trust for Scotland (NTS) says the adult seabirds are not finding enough food around the archipelago, west of the Outer Hebrides.
With about half of Britain's population, few of the World Heritage Site's puffins are coming of age, which some conservationists say is leaving the entirety of the birds' population "verging on catastrophe".
The most recent survey suggests there are 284,528 Atlantic puffins on St Kilda's uninhabited islands, which accounts for around a quarter of the entire UK population.
Yet barely over half of the eggs hatched fledged chicks last year. While that figure of 57 per cent represents an increase on 2005's all-time low of 26 per cent, it remains perilously below the average, which stands at about 71 per cent.
Across other sites in Scotland, the threat to the puffin population is equally severe.
The ruthlessness of nature is largely to blame. Conservation experts have told The Scotsman, the issue is inextricably bound to the mismanagement of Scotland's waters.
Over the past two decades, the surface temperature in the southern North Sea has risen by 2C.
It appears at first to be a negligible increase, but it is playing out a complex choreography on the food needed during the seabirds' breeding seasons.
Whereas once the puffins, also known as sea parrots, thrived on the likes of oil-rich sand eels, young herring, or sprats, they are now forced to eke out what little nutritional value is available from snake pipefish, which until recently, was rarely seen.
The rise in temperature has led to plankton regime shifts and a change in tidal cycles, which in turn affects fish like sand eels.
Sarah Money, the NTS seabird ranger on the islands, forecast a grim future for the birds.
"The chicks are just dying of starvation, with hundreds of emaciated bodies lying around outside the burrows," she said.
"Since July, the parents have been bringing back mainly pipefish, which the chicks can't swallow. Many of the burrows contain piles of uneaten, rotting pipefish."
The crisis, according to Becky Boyd, is at tipping point. Dr Boyd, a marine policy officer with the Scottish Wildlife Trust, pointed out that at present, only 0.01 per cent of Scotland's water is protected by legislation, an area the size of Kensington Gardens. That must increase in order to protect all of Scotland's natural environment and wildlife, she stressed.
"The management of seas in Scotland is in absolute chaos, and the future of puffins is verging on catastrophe as a result," Dr Boyd said.
"This is not just about dying puffin chicks and disappearing sand eels, it's a sign that Scotland's seas are pressing the red destruct button as a result of human pressures. The Scottish government must create a network of marine reserves where wildlife can recover, and press ahead with a Scottish marine bill with conservation at its heart to revive our seas and support all the livelihoods that depend upon them."
The Royal Society for the Protection of Birds Scotland believes seabird breeding has been "disastrous" this year, singling out Orkney and Shetland in particular.
The problems facing puffins is not isolated to St Kilda. On Fair Isle, the most remote inhabited island in Britain, breeding success fell to the second lowest level on record last year. The Fair Isle Bird Observatory found about four in ten adult birds were returning to their colonies to try and feed their young with snake pipefish. In one burrow alone, conservationists recovered a total of 85 discarded pipefish.
Rangers on the Hebridean island of Canna and St Abbs Head in the Borders, which are also owned and managed by NTS, have also reported an increase in pipefish, a scourge for puffins and kittiwakes.
Lynda Dalgleish, the marketing manager of the Scottish Seabird Centre, has also witnessed difficulties in the Firth of Forth. There, on Craigleith island, conservationists have enjoyed a rise in the puffin population over the past five years after hundreds of volunteers helped remove tree mallow, a non-native plant, which had grown over the entrances to burrows.
The scourge of snake pipefish, however, remains a threat to puffins and kittiwakes.
"It's horrible to watch these little birds unable to eat," Ms Dalgleish said. "The parents are bringing back the pipefish thinking they are sand eels, but the young just can't digest them.
"It's very distressing. We've had visitors watching live webcams of the young trying to swallow the pipefish, and it's very, very sad."
Ms Dalgleish argued that a blanket ban on the fishing of sand eels would help restore the puffins' food source.
"The numbers have to be allowed to fully replenish so the puffins can feed their young," she added.
The prevalence of snake pipefish is a relatively recent phenomenon. As Ms Money explained, in the waters around St Kilda, the close relative of the seahorse was rarely seen before the turn of the century, but has become "increasingly common".
"It is feared that this is another symptom of climate change," she said. "They have been extending their range southwards."
Richard Luxmoore, head of nature conservation at NTS, warned: "We are now experiencing major changes in the sea that were quite unpredicted.
"Shifts in plankton populations and a reduction in sand eels have been relatively well studied, but nobody foresaw the invasion of the snake pipefish or the dramatic effect it would have on our seabirds.
"In an ecosystem as complex as the sea, the major disruption caused by climate change can have a huge impact on humans and wildlife alike."