Dead worms on tarmacadam driveway

I have a one acre lawn. It was sown in September 2009. It is divided by a long tarmacadam driveway. The tarmac was done in May 2010. Since the rainy weather started I notice hundreds of dead long worms presumably earthworms on the tarmac. The crows etc eat most of them. I have not seen anything like this before and wonder is it normal or what might be going on. They would be much more useful doing their work in the ground and I hate to see them all dead. Look forward to hearing your views on this one.