Rare butterfly species are winging their way back to Oxfordshire because of last year’s warm spring. Butterfly experts say the conditions last spring were perfect for the insects, which emerged weeks earlier than normal, as they appealed for people in Oxfordshire to help monitor species this year.

Data collected by the UK Butterfly Monitoring Scheme revealed population rises for a number of species that have declined in recent years and scientists are hoping there will be similar increases this year, following hot weather in March.

Volunteers have been collecting data from about 1,000 sites acros the UK and ecologist Dr Marc Botham, from the Centre for Ecology and Hydrology in Benson Lane, Crowmarsh Gifford, said people should look out for some scarce species in Oxfordshire.

He said: “Increasingly warm spring weather in recent years has really benefited a number of scarce species.

“And volunteers have worked hard to improve the condition of current habitats by cutting back woodland to create open areas where violets and other plants can grow.

“The more information we get from the public the more steps we will be able to take to help protect rare species.

“The hot weather in March will have helped but it could be quite cold in April and May so that could set the spring butterflies back a bit.”

Dr Botham added that people can look out for the grizzled skipper throughout Oxfordshire at sites including Aston Rowant and Aston Upthorpe Downs, and the dingy skipper, pictured, at sites including Swyncombe Downs in the Chilterns. He said: “Both are localised scarce species that have shown significant long-term declines but had a superb year in 2011.”

Dr Botham added: “The silver-spotted skipper is worth looking out for on any chalk grassland with short-grazed turf.”

According to Butterfly Conservation, which is working with the CEH on gathering data for the monitoring scheme, the dry weather has provided “perfect conditions for spring specialists, enabling them to benefit from extended flight periods”.