Cultural traditions, not genetics or environment, inform nest architecture among white-browed sparrow weaver birds

Challenging long-held beliefs that bird nest building is solely influenced by genetics or the environment, researchers report that the white-browed sparrow weavers of the Kalahari Desert, Africa, build nests with distinct architectural styles that reflect group-specific cultural traditions. “Behavioral traditions in birds have been well documented for song, migration, foraging, and tool use. Here, we add building behavior and show that architectural styles emerge from birds that build together,” write the authors. Humans are well known for their culture-specific architectural traditions. While these cultural traditions are considered a hallmark of human societies, humans are not the only animals to build structures or display cultural traits. A growing body of research shows that animal culture can explain much of the variation observed in behavior. Both variation and conformity in bird nest-building are often thought to be driven by either innate predispositions or environmental factors, with evidence primarily supporting the latter. For instance, birds in colder climates tend to build larger, more insulated nests. However, studies have shown that birds may adjust their nest-building behavior based on previous experience and social learning rather than just responding to environmental conditions. These findings suggest that individual experience, social information, and cultural processes may also play significant roles in the variation observed in avian nest construction.

According to Maria Tello-Ramos and colleagues, white-browed sparrow weavers – social birds that build several single-occupant roosts and nests throughout the year – offer a unique opportunity to study the repeatability and variation in morphology of structures built within and among different groups. Tello-Ramos et al. measured various aspects of nearly 450 structures built by 43 different groups of sparrow weavers across two years in the Kalahari Desert and found that despite living in proximity and having similar genetics and habitat conditions, each group had its own distinct building style. For example, some groups build short, thick structures while others build structures with longer entrances and exit tubes. The findings show that these differences were not influenced by factors like bird size, tree height, or weather and remained consistent even when birds moved between groups, suggesting that migrant birds conform to the building style of their new group. This suggests that social learning and group-specific preferences across generations drive these architectural styles rather than genetics or environmental factors.