Sand martin – Riparia riparia
or European sand martin, bank swallow in the Americas, and collared sand martin in the Indian Subcontinent, is a migratory passerine bird in the swallow family. It has a wide range in summer, embracing practically the whole of Europe and the Mediterranean countries, part of northern Asia and also North America. It winters in eastern and southern Africa, South America and the Indian Subcontinent.

The 12 cm (4.7 in) long sand martin is brown above, white below with a narrow brown band on the breast; the bill is black, the legs brown. The young have rufous tips to the coverts and margins to the secondaries.

Its brown back, white throat, small size and quick jerky flight separate it at once from similar swallows, such as the common house martin (Delichon urbicum), the American cliff swallow (Petrochelidon pyrrhonota) or other species of Riparia. Only the banded martin (R. cincta) of sub-Saharan Africa is similar, but the sand martin only occurs there in (the northern) winter.

its twittering song is continuous when the birds are on the wing and becomes a conversational undertone after they have settled in the roost. The harsh alarm is heard when a passing falcon, crow or other suspected predator requires combined action to drive it away.

It sounds like this
Recording by Marco Dragonetti from Xeno canto