Valentines Day is always a good reminder that birds are already seeking out secret love nests.  It is great when birds are able to make their own nests, in hedgerows, trees and tree trunks (a good reason to leave rotting trees in situ), but supplementing natural habitats is always worthwhile.  If you want to know how to build a bird box there are lots of courses up and down the country, in Cheshire, Northumberland and elsewhere.