Satara seems to be one of the easiest spots to "study" these birds as there are numerous nests in the camp near the huts.
Buffalo weavers are unique amongst all birds in that both males and females possess a phalloid organ, a phallus-like structure anterior to the cloaca, the terminal region of the gut into which the intestinal, urinary and genital canals open. Observations and experiments with red-billed buffalo weavers in captivity revealed that the phalloid appendage functioned as a stimulatory organ which necessitated protracted copulation in order to induce male ‘orgasm’ and ejaculation, a feature also unique to this species.
The species is very much a polyandrous breeder with cooperating males fathering chicks in the same nest, feeding the young and defending the nest together. Brief copulations happen a lot both with females and with other males where no sperm transfer takes place. A minority of copulations successfully transfer sperm when repeated mountings over a period lasting as long as 30 minutes took place. It follows that there is a lot of competition among males to be fathers, even though genetics again tells us that the cooperating territorial males sharing a female are at least sometimes related (though not usually close relatives). What the phalliod organ actually does isn't entirely clear - it's not the route for sperm to flow through - but apparently it needs stimulation before females can be inseminated by the male. Buffalo weavers are the only birds to experience anything that looks like an orgasm (but only after repeated copulation), and only at the point of ‘orgasm’ (the main effect seems to be causing the male to pull the female closer to him) is sperm transferred to the female.
Red-billed buffalo weavers breed in compound nests made up of separate "lodges", each with a number of nesting chambers within them. The males are polygamous, each controlling 1-8 nest chambers and up to about 3 females. Usually there is one dominant male in a colony who has the most females and egg chambers, while other males may have one female and a few chambers. The males vigorously defend their lodges against other males, using aggressive displays and calls and females within the harem do not tolerate each others presence in their egg chambers. Colonies may use a different system altogether, with two males cooperating with each other to build the nest, both defending the territory and helping to feed the chicks.
The nests are constructed by the males entirely of dry, thorny twigs. Some of the size of the twigs are enormous and the bird has to balance it carefully before he is capable of flying off with it, like this bird seen collecting building materials at Satara. Then each egg chamber is completed by a female that will line it with dry grasses and other soft materials.