Some birds are said to be too hungry to breed

Fears have been voiced by two leading conservation groups, the Royal Society for the Protection of Birds (RSPB) and the National Trust for Scotland (NTS).

Experts have warned the outlook on their nature reserves is looking grim, with delays in nesting and low numbers affecting most species.

In the Northern Isles last year scores of birds failed to raise chicks.

Scientists have predicted that the huge colonies known as "seabird cities" may shrink again this year.

No kittiwakes have laid eggs yet on Fair Isle and only seven guillemot eggs have been found where there should be hundreds.

We are very concerned about the prospect for the months ahead Kara Brydson RSPB Scotland

A lack of food, possibly linked to global warming and rising sea temperatures, is believed to be to blame. Many starving birds are too hungry to lay eggs.

However, ecologists have acknowledged this spring's unseasonal weather may have caused delays.

Researchers at the RSPB admit it is still very early to make concrete predictions but they warn initial signs are not good.

Spokeswoman Kara Brydson said: "We are very concerned about the prospect for the months ahead.

"Last year was disastrous for Scotland's seabirds and all we can do at the moment is hope that the situation improves as the summer progresses but we are not optimistic."

Robin Pellew, of the National Trust for Scotland, added: "At the trust's east coast colonies, from St Abb's Head all the way up to Unst and Fair Isle - where seabirds attract a significant amount of tourism - the situation is looking bleak.

"If the seabirds fail to breed again in these areas the numbers of kittiwakes, puffins and other species could collapse in the near future."

Rising sea temperature

He added: "Evidence is mounting that global warming is to blame for the problems that the seabirds in Scotland are experiencing.

"Rising sea temperatures have been strongly linked to the decline in the number of sand eels upon which seabirds feed."

Ornithologists revealed a year ago that no Arctic tern or kittiwake chicks had been reared in southern Shetland.

Sea temperatures have risen by up to two degrees in the past 20 years and that may be causing the sand eels and the plankton on which they depend to move to cooler waters.