Weavers: Ploceidae

Weavers are energetic and noisy, especially when gathered together in flocks, which is a large majority of the time for some species and most of the time for a few. Individuals of some weaver species may live alone, but even they periodically form social groups of up to a thousand birds.

Weavers forage in groups, and feed by picking grass seeds, insects, and spiders off the ground, or perching on stalks of grass and yanking seeds from the stalk, crushing all but the hardest seeds with their powerful beaks. Some snag insects in mid-flight. Some weaver species stay more or less in one place, others migrate to greater or lesser degrees.

Weaver voices and songs are long-winded, complex, and vary with circumstances, including displays of aggression, mating, and warning. The song of the red-headed weaver has been transcribed as "chu-tsee-tsi, chu-tsi, tsee-tsi, tswi-tsi-tswee, tzirrrr," morphing into "tchu-thi-tseee-iiiiii-i, swizzzzzzz" or "sizzi-sizzi-sizzi-sizzi."

Reproduction types vary among species and reflect the sort of nest-building used by each. One species, the cuckoo finch, is a brood parasite, similar to cuckoos, cowbirds, and honeyguides. The cuckoo finch lays her eggs in other birds' nests. Consequently, her eggs are treated as family by the receiving birds, allowing the cuckoo to reproduce without caring for her own young. A few weaver species have individual, isolated nests for breeding couples, but most species build colonial nests, either individual nests in one tree, or a giant common nest. Entrances are on the bottom or sides. The communal nest of the social weaver can hold up to three hundred breeding pairs and may reach 10 feet (3 meters) in height and 15 feet (5 meters) in width.

Weavers living in colonies may be polygamous (puh-LIH-guh-mus; one dominant male, several breeding females), polygynous (puh-LIJ-uh-nus; one dominant female, several breeding males), cooperative (two or more males mate with all females, males help care for the young), or monogamous (muh-NAH-guh-mus; one breeding pair), but monogamous pairs may inhabit communal nests. More than one of these systems may be used even within one species. In communities with several breeding pairs, a dominant male mates with the largest number of females possible.

Weavers build nests in large, isolated trees and on power line support towers and windmills. In most species, the male builds the nest or adds onto a communal nest, then invites and entices females to mate with him and move into the nest to raise the young. Large birds of prey may build nests on top of communal weaver nests, partially camouflaging the raptor nest and lending some protection to the weavers. The birds finish the entire structure with a roof of intertwined leaves on twigs, for repelling rain.

The red-billed buffalo-weaver shows both polygamous and cooperative breeding behaviors. In polygamous systems, one male rules and defends up to eight chambers, each with a female and young, in a single large, communal nest. In the cooperative method, two males build and defend nests, and feed the young.

Weavers aggressively defend their nests, not only from predators but also from other members of their own species. The defenders can distinguish nest-family members from strangers of the same species, threatening and driving them off. One or more males are the principal defenders and if they are away from the nest, a female may take over the task of defense.

Female weavers lay two to eight eggs per clutch. The eggs hatch in about fourteen days. In monogamous species, both parents raise the chicks, while in polygamous and polygynous species, adults other than the parents may help care for the young.