From Wikipedia: The Common House Martin, sometimes called the Northern House Martin or, particularly in Europe, just House Martin, is a migratory passerine bird of the swallow family which breeds in Europe, north Africa and temperate Asia; and winters in sub-Saharan Africa and tropical Asia. It feeds on insects which are caught in flight, and it migrates to climates where flying insects are plentiful. It has a blue head and upperparts, white rump and pure white underparts, and is found in both open country and near human habitation.

Both the scientific and colloquial name of the bird are related to its use of man-made structures. It builds a closed cup nest from mud pellets under eaves or similar locations on buildings usually in colonies, but sometimes fouling below nests can be a problem.