Puffins may look like clowns but have just proved once again that they’re excellent time-keepers.

April 14 is traditionally the day when thousands of the seabirds land on the cliffs at Lovund island off north Norway at the start of the mating season. They sometimes land a day or two on either side of the date, first gathering in vast flocks after the long winter spent out at sea, but April 14 is so reliable that it has become a tourist attraction.

“It’s just instinct,” says Torill Olaisen, who works at the local hotel on the island. “It could be the length of the day, it could be the amount of moisture in the air, it may be access to food. No one knows how they do it.”

She said that, once the eggs hatched, the puffin colony on Lovund could total 200,000 birds, one of the biggest along the coast.

This year they arrived like clockwork, at 7.15 p.m. in the evening on April 14 (I originally wrote this blog in the morning, wondering if they’d be arriving on time this year…I shouldn’t have doubted them: they were).

Warmer sea and air temperatures in the Arctic region in recent years, apparently part of global warming, do not seem to have disrupted their arrival date so it may be steered by other factors.

So how did they manage to figure out that 2008 is a leap year and humans have added an extra day to the calendar?

Any ideas how they do it?