I just found out that Martins overwinter in Africa, but dont breed there, they return to Europe to breed. I alway thought they bred in Africa as well. Also wondered wether a few pairs on the house have had a third clutch this year, it has been a remarkably good season this year, probably helped by more insects than I have seen in a long time, also I'm sure the availability of nest boxes has helped tremendously, less time building, they can get on with the job of nesting a lot quicker. These dry springs dont help, a lot less clay mud around & silt from farm ponds, the nests they do make seem to contain a very sandy consistency, most dont last the winter. I am still amazed by these little critters, & how little we know about them.