This little chap and his missis (or is it the other way round?) have already raised one family this year and now they're raising another. They have some very hungry chicks because they're bringing food to them constantly.
They're pied wagtails for those of you not familiar with them.
@pamelaclarke Thank you Pamela. Yes they are but they seem happy. Is it possible that the first brood help to feed the second brood (a bit like house martins) and that this is a young one which still has a few juvenile feathers?