I assumed this would be easy to find based on what I remember but I somehow have not yet found it. I am sure I watched this in the 1990s sometime but I can't exactly remember if it was then or early 00s but I think it was the 90s but I can't remember if the program came out when I saw it or before then. I am nearly sure it was narrated by David Attenborough but I have not found it if it was so maybe it wasn't. It was a documentary (BBC I think) about the migration of Swallow birds (Hirundo rustica) from Africa to Britain and it followed the Swallows as they migrated. One part mentioned rainy weather delaying their migration and I am sure I saw a swallow resting in bushes or on a tree under leaves to try and get out of the rain and I think it also mentioned some Swallows not surviving the journey, possibly killed by electrical wires, exhaustion and predators or some other reason. Anyone know what this documentary was?