They will help collate roadside casualty figures as part of an investigation led by a team from the School of Biological Sciences at Bristol University.

The team is involved in a three-year project to assess the importance to wildlife of Britain's network of roadside verges.

Killing zones

The casualty survey will concentrate on birds of prey but will also include foxes, badgers, otters and others wild animals.

The aim is to understand the "killing zones" and offer suggestions on better management to aid the threatened species.

The most endangered bird of prey species include the red kite, white-tailed eagle, marsh harrier, goshawk, sparrowhawk, buzzard, osprey, kestrel and peregrine falcon.

Research will focus on more than 20 miles of the A303 dual carriageway between Wincanton and Ilminster, Somerset, already the source of a rich wildlife database from previous studies.

The barn owl: Threatened by changing farming methods

The team is seeking volunteers, particularly from the Mammal Society and from the Hawk and Owl Trust, to help them gather national data for comparison.

"We need to see how representative our Somerset site is," said the project co-ordinator, Lincoln Garland, a PhD researcher.

"We are looking to reduce the casualties and we need first of all to understand why there are such high numbers of deaths."

Grass verges

Preliminary studies showed that the verges may prove a richer habitat than was previously thought.

Researchers have been surprised by numbers of wood mice, field voles and the scarcer harvest mice and water shrews.

Mr Garland said: "We hope our work will establish just how valuable the roadside verges are and provide ideas for better management to reduce casualties, particularly among the younger birds of prey."

Red kite soars

Concerted efforts by organisations like the Royal Society for the Protection of Birds have resulted in the dramatic recovery of the red kite in the last year.

Reintroduction projects in conjunction with English Nature, Scottish Natural Heritage and the Welsh Kite Trust meant last year's breeding season for one of the UK's rarest birds was the best in more than 100 years.

Red Kite: Best breeding for 100 years

The demise of the UK's birds of prey is caused by several factors: egg thieves, shooting, poison, traps and pesticides.

In fact, the numbers of these feathered hunters in the countryside are an indication of the general health of the environment.

The position at the top of the food chain makes them particularly vulnerable to manmade chemicals.

In the 1960s, a sudden decline in the sparrowhawk and peregrine populations led to the discovery of the side-effects of DDT used for crop spraying. As a result, the chemical was banned.

But not everyone is keen to see an increase in the bird of prey population. In Scotland, home to more than half of the UK's peregrine falcons, pigeon racers complained that the newly replenished sparrowhawks and falcons had killed abut 70,000 racing birds there in one year.

Last August, the Scottish Homing Union lobbied MPs demanding the right to cull birds of prey.