The National Parks and Wildlife Service has said there is evidence to suggest that puffins have left Sceilg Mhichíl off the Co Kerry coast a few days earlier than previous years, but do not yet know why.

In a statement, the NPWS said the departure does not suggest any major change in the behaviour of the bird population on the island or at other colonies.

The island is a Special Protection Area for birds and every year around April thousands of puffins return to Sceilg Mhichíl to breed.

Results from the NPWS' latest survey data from May shows a count of puffins "favourable with previous counts since NPWS started monitoring puffin on the island".

In a statement the NPWS said: "Puffins are known to leave the island each year in late July and early August.

"While there is some evidence to suggest that the puffins left the island a few days earlier than in previous years, we do not yet know why this has occurred.

"There is no record of bird flu affecting the puffin population in Ireland."

The NPWS have been monitoring the puffin population on the island and at other seabird colonies around the coast since the early 1990s.

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Speaking on RTÉ's News at One, Niall Hatch head of communications with Birdwatch Ireland, said it is too early to discern what promoted the birds to leave early.

"It’s only slightly early, but it remains to be seen if it’s related to weather or possibly even related to things like bird flu or issues like that."

He explained that the birds are going to spend the remainder of the year bobbing around the Atlantic Ocean. But they leave their chicks or pufflings back in their burrows.

"They have nesting burrows, and they leave them there until they start to feel hungry. They realize that mum and dad are not coming back with food anymore. And that then prompts those chicks to then head out to sea."

Mr Hatch said they still do not fully understand why puffins behave exactly the way that they do.

"But it could be something to do with prompting their chicks to head out to sea in events of storms or something like that. But that's just speculation."

Despite recent events, Mr Hatch said puffins can live for around 30 years, so he is hopeful the birds will return. But he explained their longevity can pose other problems.

He said they know that the adult puffins have been doing quite well but it is much harder to gauge the success of the breeding, especially when it comes to the productivity of the chicks and the survival of the chicks.

"Because the puffin's nest in burrows. You cannot monitor them on the same basis that you can other sea birds that nest on cliff ledges or on open ground, and sometimes the longevity of the adults can mask the fact that a lot of the chicks actually are not surviving.

"We have seen almost complete collapses of puffin breeding at huge colonies in places like Norway and in Iceland in recent years. And there are fears that climate change may be having a big impact on them."