Little rush warbler
The little rush warbler or African bush warbler is a species of Old World warbler in the family Locustellidae.
It is found in Angola, Botswana, Burundi, Cameroon, Chad, Republic of the Congo, DRC, Ethiopia, Kenya, Malawi, Mozambique, Namibia, Nigeria, Rwanda, South Africa, South Sudan, Eswatini, Tanzania, Togo, Uganda, Zambia, and Zimbabwe. Its natural habitat is swamps.
Vocalization
Its characteristic vocalization starts slow and increases in speed; it has been described as "distinctive and loud." It occurs most often during breeding season, while raining.