Bearing in mind that some indigenous birds may rear more than one nest of chicks, do any of the migratory birds such as swallows have broods elsewhere in the world - in the same year - in addition to those they have in Britain?
I wouldn't think so Tinkerbell. By the time they've raised broods here and fed up ready for the trip back to West Africa, and then stocked up there reserves there. I think there wouldn't be enough time or food to support them! That's why they come here. For the abundance of food and the conditions to support their breeding.