As in many species, the males can be told from the females by their beautiful plumage – often a striking yellow or red but sometimes black. But it is clear that in this case, plumage is not enough to secure a mate. For on top of this, the males of each colony must compete each year in a test of skill and creativity which has made them famous: the weaving of the most elaborate nests of any known bird. Many species go about this in unique ways, and many use different materials. The buffalo-weaver of Kenya and Tanzania constructs raggedy nests of twigs while the Indian weaver bird constructs a tidy, tight-fitting mesh of roots and tendrils in a remarkable globe-and-tube shape.
As soon as mating season appears on the horizon, every male weaver bird that answers ‘the call’ begins to behave more like a labourer than a casanova, and they begin to construct nests in the hope of attracting the favour of some fickle female. But there’s no rest for the wicked: they will hedge their bets by continuing to construct nests as long as there’s somewhere appropriate to place them. Often this will involve building on a tree branch overhanging a river – a spot unlikely to be accessible to most predators. This frequently results in branches sagging from this heavy burden, as some species of weaver birds are known to build nests in groups of up to 300.
If an approaching female is not immediately impressed by the fruits of the male’s creative labours, he will chase her away and pursue a more easily-affected female. As Victorian scientists (who were always quick to anthromorphosize!) would have put it, his artistic vanity may have been wounded.
The social weavers of Namibia do live in extremely high numbers, but they do not construct individual nests. Instead, they form a continuous mat of nest material that will often overtake the entire canopy of a tree, and may last for up to a century. These are messy affairs, built as a communal effort by all the males in the colony – each bird haphazardly adding nest material to the parent mass. Such ‘apartment blocks’ may even be divided into rooms with different purposes: nesting chambers, sleeping areas for adults and feeding areas will all be kept separate.