These photos by Spencer Barrett show African sunbirds using the perch to feed on the flowers. The pictures were taken in part of a study by Spencer Barrett et al 2011 (De Waal, C., Anderson, B. & Barrett, S.C.H. (2012). The natural history of pollination and mating in bird-pollinated Babiana (Iridaceae). Annals of Botany 109: 667–679. doi:10.1093/aob/mcr172). The third photo shows a plant where the perch was removed. Note the position of the fertile stamens. One of the things the study found was that despite the presence of a specialized perch, a considerable amount of self-pollination still resulted.