Northern House Martin (Delichon urbicum)
Also called Common House Martin, the Northern House Martin (Delichon urbicum) is a migratory bird of the swallow family. I always see them flying in flock, sometimes even joining a flock of Barn Swallows. They are quite easy to distinguish from Barn Swallows though : the Northern House Martin has a bicolor glossy blue-black and pure white plumage, with a white throat and rump. It also has a much shorter tail.