Reproductive output of Blue Waxbills Uraeginthus angolensis (BWs) and Melba Finches Pytilia melba (MFs) was extremely low in the central Transvaal, South Africa, despite strict measures to limit observer disturbance. Eggs were laid in 5741% of nests built in 1985, and 2&Z% of nests in 1986. Between 0% and 20% of nests with eggs were successful, and &25% of individual eggs resulted in fledged young Predation, nest desertion and storm damage accounted for most failures. A substantial proportion of nests failed before they were visited, indicating a high rate of natural failure, and the number of nest visits did not appear to influence nest outcome. Both BWs and MFs chose well-protected, camouflaged sites, especially in the tree Acacia tortilis. However, neither dense thorns nor dense foliage, nor the presence of commensal wasps (Polistes and Ropalidia), safeguarded nests from failure.