The coronavirus lockdown has halted efforts to help field crickets – but has helped scientists confirm that their bid to protect the rare insects is already working.

Lockdown rules meant the RSPB had to abandon a final bid to translocate field crickets to restored habitat on two reserves, to help bolster new populations of the threatened species, the wildlife charity said.

But wardens carrying out fire and livestock checks at the Pulborough Brooks and Farnham Heath reserves this month heard field crickets singing at the release sites, a sign that previous releases have led to successful breeding.

Any crickets, which have an annual life cycle, heard calling this year must be the offspring of insects released in previous years.

And it was only because no new releases could take place this year, so no newly introduced crickets could be singing, that scientists could confirm that the previous translocations are working, the RSPB said.

The insects were once the soundtrack to summer evenings, but numbers dropped to just 100 individuals at a single location in the 1980s in the face of changes to how land was managed and loss of their grassy heathland homes.

Conservation work over the past 25 years has put them on the road to recovery, with populations in eight locations across Surrey, Sussex and Hampshire, but they are still one of the UK’s most threatened species.

The RSPB and conservation agency Natural England have been working to boost populations of the crickets since April 2017 as part of the National Lottery-funded Back From The Brink programme to help rare wildlife.

The scheme aims to establish a new colony at the Pulborough Brooks reserve in West Sussex and extend an existing colony at Farnham Heath in Surrey – with the RSPB now hailing the success of the scheme.

Using a technique known as “tickling” with a blade of grass, experts encourage young field crickets, or nymphs hatching underground and beginning to emerge, out from their burrows so they can be caught and moved to new areas.

The scheme allows youngsters from an established colony to be moved to a specially selected area where it is hoped a new colony will be formed.

Conservationists say that creating new populations is vital as it reduces the risk of losing the entire species to a single catastrophe such as a fire.

RSPB senior ecologist Jane Sears said: “There is something quite evocative about the soft chirping of a cricket on a warm summer’s evening.

“Unfortunately, with field crickets on the verge of extinction, we almost lost their song.

“So it was with a heavy heart we cancelled our final chance to bolster the population with the Back From The Brink project, unsure of how our previous attempts to create new breeding sites had fared.

“The news that our new colonies are doing well has given us hope the species can be brought back from the brink.

“We have seen how, with the right conditions, the species can thrive.”

Although the Back From The Brink programme ends this year, the RSPB will continue to monitor field cricket populations.