TENS of thousands of volunteers are expected to take part in this year's Big Butterfly Count.

This survey, run by the Lulworth-based Butterfly Conservation charity, gets underway on July 19 and runs until the end of August.

Television presenter and naturalist Nick Baker said: "Butterflies are incredibly sensitive indicators of the health of our environment.

"Across the UK most species of butterflies and moths are in some kind of decline.

"But the good news is you can do something about it, you can do something to help by taking part in Butterfly Conservation's Big Butterfly Count.

"By doing so you will be able to help them work out how best to help the butterflies.

"On top of that it is a great way of getting outside and having fun."

To take part volunteers need to count butterflies for 15 minutes during bright, preferably sunny, weather during the big butterfly count.

This time of year has been specifically chosen by butterfly experts, because at this time of year most butterflies are at an adult stage of their lifecycle.

A count spokesman explained: "Records are welcome from anywhere – from parks, school grounds and gardens, to fields and forests.

"If you are counting from a fixed position in your garden, count the maximum number of each species that you can see at a single time.

"For example, if you see three Red Admirals together on a buddleia bush then record it as three, but if you only see one at a time then record it as one, even if you saw one on several occasions.

"This is so that you don’t count the same butterfly more than once."

Then send in sightings online at bigbutterflycount.org, or by using the Butterfly Conservation's free Big Butterfly Count app.

The survey, which is backed by Butterfly Conservation president Sir David Attenborough, takes place from July 19 until August 11.

Last year more than 100,000 people took part in the count.