As spring gets under way, the RSPB is asking people who spend time in the Yorkshire Dales to keep their eyes peeled for hen harriers, the country’s most threatened bird of prey.

Now in its seventh year, the conservation charity has relaunched its Hen Harrier Hotline in the hope of discovering where the birds are potentially breeding.

The uplands should have at least 320 pairs of breeding hen harriers but last year not a single chick was raised in the whole of England.

Amanda Miller, conservation manager for the RSPB in Northern England, said “This lack of breeding success is not through lack of effort. The male is famous for his spectacular courtship display known as skydancing in which he tries to attract a female with a series of high altitude swoops and somersaults. It’s like watching nature’s equivalent of the Red Arrows.”

The main reason hen harriers have reached crisis point is that the species suffers from ongoing illegal persecution.

In addition to their diet of small birds and mammals, hen harriers sometimes eat grouse, which brings them into conflict with the driven grouse shooting community.

This particular type of shooting requires large numbers of birds and some game managers feel they must illegally kill or disturb harriers to protect their stock.

A Government-commissioned scientific report, published in 2011, found that illegal persecution continued to be the biggest single factor preventing the hen harrier’s recovery in England – a fact confirmed by the recovery of shot hen harriers in both the Yorkshire Dales and Aberdeenshire in 2012.

“The English hen harrier is on the edge of extinction as a breeding bird. It is therefore critical that we are able to locate and protect any birds that may be nesting,” added Ms Miller.

“As hen harriers tend to breed in remote moorland areas, we rely on walkers, cyclists, and other people who spend their free time in the uplands to help our on-the-ground team by letting us know if they see one.”

Male hen harriers are an ash-grey colour with black wing tips and a wingspan of just less than a metre. They are sometimes known as “ghostbirds” because of the pale colour of their plumage.

Female hen harriers are slightly larger, owl-like in appearance, and have a mottled brown plumage, which camouflages them when they nest on the ground. They have obvious horizontal stripes on their tails, giving them the nickname “ringtail” and a patch of white just above, on the rump.

The Harrier Hotline number is 0845 4600121 (calls charged at local rate). Reports can also be e-mailed to henharriers@rspb.org.uk. Reports of sightings should include the date and location of sighting, with a six-figure grid reference where possible.

The Hen Harrier Hotline is part of Skydancer, a four-year RSPB project aimed at protecting and conserving nesting hen harriers in the English uplands. The project is funded by the Heritage Lottery Fund and United Utilities, with additional support from the Forestry Commission.

For more information about the project, visit rspb.org.uk/skydancer.