Puffins nesting at Bempton Cliffs in East Yorkshire have declined by two-thirds across the whole colony, according to the latest census.

However other seabirds like guillemots and gannets have increased dramatically - bucking the trend elsewhere.

Officials that puffins are notoriously difficult to count because they nest in burrows, cracks and crevices, and the figure may only give a rough picture of what is happening.

However the decline mirrors that seen on the Isle of May and the Farne Islands, in Northumberland, raising concerns about their future.

Site manager Ian Kendall said the RSPB were desperate to find out the cause of the decline but studying the birds was an "absolute nightmare."

The decline in sand eel populations - caused either by climate change or industrial fishing or the weather or a combination of the three - the main food source for many seabirds including puffins, could be to blame. He said: "Gannets can exploit different food sources - they are pretty good at foraging the oceans and produce one chunky chick.

"We really don't know where the puffins go. I have never seen one in their winter plumage.

"They go out well into the oceans and don't come back to land from July through to April. Further research is needed to draw a definitive conclusion."

Bempton Cliffs is home to England's only mainland gannet colony and has seen numbers explode since 1988 when there were only 20 pairs.

Now 20 years later, there are a staggering 6,000 pairs – with a further 2,500 youngsters trying to establish nesting sites.

Guillemots have increased by 25 per cent since the last full colony count in 2000. This year, nearly 60,000 birds were counted on the cliffs, making RSPB Bempton Cliffs and Flamborough Head the third largest colony in the UK.

The reserve still has the largest kittiwake colony in the UK, with nearly 38,000 pairs nesting. However, there's been a 13 per cent recorded decline since 2000.