SUMMARYA comparative study was made of social organization during breeding among the genusMalimbus. InM. nitens, the male chooses the nest site, builds the nest alone, guards the nest during incubation, and feeds the young; the female incubates, broods alone and with the male feeds the young. InM. malimbicus, the male chooses the nest site, builds the nest with the female and guards the nest; the female builds the nest with the male, but incubates alone. InM. racheliaeandM. cassini, the nest is built by one female and a multi‐male party of two or three. One male drives off the other males when the nest is completed. One male and one female incubate alternately. The female seems to be the leader of the building group, and works like a male. InM. coronatus, the nest is built by a mixed party of males and females (3–6 birds), all working together without any overt leadership. Only one male and one female however, incubate, brood and feed the young.In their morphology and behaviour,Malimbusspp. are close to the weaver birds of the genusPloceus. M. nitensseems the least evolved species whileM. cassiniandM. coronatusare behaviourally the most evolved. In the last species, which has a very elaborate nest, the pair of breeding birds is helped by one to four other birds. These helpers are birds in full adult plumage, and are probably capable of breeding and may do so at another period in the long breeding season of at least six mon