HOLIDAYMAKERS heading to the sea this summer are being asked to look out for common blue butterflies to see if the struggling species is faring better at the coast.

The common blue is widespread across the UK but experts warn it is in decline as more intensive agriculture and lack of woodland management reduces its habitat.

Populations of the common blue, the most widespread blue butterfly in the UK, reached their lowest level on record in 2012, Butterfly Conservation said.

The wildlife charity has teamed up with the National Trust to ask the public to look out for the species at the coast, which provides habitat the butterfly needs.

Seaside visitors are being urged to record sightings of the common blue as part of this year's Big Butterfly Count, in which nature lovers spot and record 18 species of common butterflies and two day-flying moths over three weeks of summer.

The main food plant for the common blue caterpillar is the common bird's foot trefoil, a low-growing plant which likes open, warm, sunny conditions and can get easily out-competed by grasses, nettles and brambles, Butterfly Conservation's Richard Fox said.

The shallow, poor soils found around the coasts benefit bird's foot trefoil and other wildflowers which the butterfly can use, and coastal eroded areas can be easily colonised by such species, he said.

"The common blue needs sunny, flower-rich vegetation, exactly the kind of vegetation that has been pushed out of farmland with intensification and pushed out of woodland with a lack of woodland management which has led to darker, shadier woods.

"It's a really widespread butterfly but it has undergone major declines in the long term as we move from a low-intensity agricultural landscape to a high-intensity agricultural landscape.

"They do occur across the country, and you can just about find them in the prairie farmland of Cambridgeshire but many of the really big colonies are on chalk grassland nature reserves or around our stunning coastline," he said.

To mark 50 years of the National Trust's Neptune Coastline campaign to protect the UK's coasts, which has seen it acquire and look after 775 miles of coastline, the trust is encouraging people to take part in the Big Butterfly Count at its coastal properties.

Matthew Oates, National Trust butterfly specialist, said: "This is a great opportunity to add some useful butterflying to your family seaside holiday while you are out on a walk along the coast or wandering through some sand dunes.

"Common blues love the extra heat of sunny coastal grasslands and also like to breed in farm fields sown with white clover along the coast.

"We'd love to know where our top coastal common blue colonies are, and what else you may see."

Other common butterfly species including the marbled white, speckled wood, gate keeper, six-spot burnet and holly blue can be found along the coasts.

:: To take part in the Big Butterfly Count, people just need to find a sunny place and spend 15 minutes counting all the butterflies seen, submitting records online at www.bigbutterflycount.org