For the past year the search has been fruitless. From his base in Malvern, Dr Birks keeps tabs on the pine marten hunt, mainly concentrated in Wales. Every time he gets a convincing report that a dead pine marten has been spotted on the road, one of his small network of volunteers goes out to investigate.
But to no avail. The elusive mammal - some say pine martens are extinct in this country outside Scotland - continues to evade him.
However, Dr Birks is not deterred. "The fact that we are getting so many good quality reports of sightings - 15 in the first eight months of this year - is heartening," he said.
"From the quality of these sightings we believe we are right in our conviction that some small residual colonies of pine martens exist outside Scotland, particularly in Wales.
"We think that pine martens have returned in such numbers in Scotland since the Victorian and Edwardian days of trapping and shooting, because of reforestation and a reduction in persecution. However, both these factors exist in England and Wales and there are plenty of hilly, craggy areas, especially in Wales, which provide just as good a habitat as forest. Yet they appear to be doing badly here. If only we could trace these pockets in Wales and in the areas in the northern half of England where we believe pine martens exist, then we might be able to help improve their habitat."
To Dr Birks the task of picking shattered animal bodies off roads and intricately examining them is not overly gruesome. For four years he cut his teeth on a similar project, tracking the advance of the polecat throughout England and Wales. Much valuable evidence for that study was gained through sightings of bodies. From these, Dr Birks was able to establish the recolonisation patterns of this other elusive native mammal.
Not that there are any signs of pine martens recolonising. Indeed the main object of Dr Birks' study is to discover why the species has been doing so badly outside Scotland.
He plans to operate in much the same way as he did with the polecat study, tracking the animals' incidence through sightings of dead and alive specimens and reporting back to his employers, the London-based Vincent Wildlife Trust, for whom he will eventually produce a report.
Finding a body is not the only means of proving the pine marten exists in England and Wales. Dr Birks' colleague, John Messenger, has been working on baiting stations - tunnels with a lure at the end. As the animal exits after grabbing the lure, a small piece of hair is removed. This can be examined under a microscope to check whether it belongs to a pine marten.
Then there are scats - the droppings. Sweeter, herbier and less offensive than those of the polecat, these, too, can be analysed. Yet Dr Birks feels that he and John Messenger are now getting so close to their first definite Welsh sighting that they will probably not have to resort to searching for scats.
"The pine marten is part of the British natural heritage," Dr Birks added. "And now that persecution has ceased and they are highly protected, we ought to try harder to accommodate them. Like polecats, badgers, foxes and red squirrels, they have been here continuously since the last great Ice Age - it is important that we should try to encourage them. "It is frightening that we know so little about pine martens. And at present, we can't get close enough to them to find out more."
Reports of possible sightings in England and Wales should be made to Dr Birks at 3, Knell Cottages, Harcourt Road, Malvern WRI3 5PS (01684 575876) or John Messenger at 16, Ithon Close, Llandrindod Wells, Powys LD168B (01597 825536)Reuse content