A 16 page booklet titled "Birds and Environmental Change: building an early warning system in South Africa" has been produced by South African National Biodiversity Institute (SANBI) and the Animal Demography Unit (ADU) of the University of Cape Town, with the financial support of the Royal Danish Embassy, Pretoria. There are 9 case studies, mostly of birds but one study is of the Prince Edward Islands. The Red-billed Quelea features as a bird that is expanding its range in the Western Cape in response to environmental changes in South Africa (see page 6 of the booklet). A pdf is available here.
To see recent records of quelea that have been submitted to the ADU, and more quelea links, see here.