White-browed sparrow-weavers

When people visit Tswalu Kalahari Reserve they may wonder at the Dr Seuss-like structures built by White-browed sparrow-weavers (Plocepasser mahali). Not especially colourful or therefore noticeable, White-browed sparrow-weavers turn out to be quite interesting. Susan Healy, Andy Young and their research groups (from the universities of St Andrews and Exeter) are investigating the building behaviour of these birds, in which the dominant pair in a group are thought to cooperate to build structures. The first question they sought to answer was how these two birds cooperate to build a functional roost or nest. To answer this question the researchers have observed nest-building techniques and have measured more than 600 of the structures built by 40 families. If it was interesting to ask how two birds cooperated to build a functional structure, things became a lot more complicated when it became clear that all of the family members build. Even more surprisingly, the researchers have discovered that structures built by one family look different to those of its nearest neighbours, and some families have their own distinctive ‘architectural style’.

After accounting for a variety of plausible factors (e.g. environmental variation, genetic relatedness, social interactions) it looks as if the birds are doing something very surprising: it looks like the migrants conform to the architectural style of their new family. The researchers are now looking to determine whether conformity does explain weaver bird architectural styles: if it does, this would be the first time that conformity in building behaviour would have been seen in a bird.