The social weaver bird create nests than can weigh 1 ton & house 200 birds in individual chambers; their cooperative behaviors include chick rearing & defense against snakes & falcons

Not even scientists can tell these birds apart. But now, computers can. Erik Stokstad. Science Magazine, Jul 28 2020. https://www.sciencemag.org/news/2020/07/not-even-scientists-can-tell-these-birds-apart-now-computers-can

Project: Cooperation and population dynamics in the Sociable Weaver. Cape Town University, 2019. http://www.fitzpatrick.uct.ac.za/fitz/research/programmes/understanding/sociable_weavers 

The aptly named Sociable Weaver Philetairus socius is a highly social species that is endemic to the Kalahari region of southern African. As the common name suggests, these weavers work together to accomplish diverse tasks, from building their highly distinctive thatched nests to help raising the chicks and defending the nest and colony mates from predators. Their fascinating social structure and different types of cooperative behaviour make them an ideal study model to investigate the benefits and costs of sociality and the evolutionary mechanisms that allow cooperation to evolve and be maintained. 

Cooperation represents an evolutionary puzzle because natural selection is thought to favour selfish individuals over co-operators. However, theory and studies in humans suggest that co-operators are preferred as social and sexual partners. Partner choice may therefore provide a powerful explanation for the evolution and stability of cooperation, alongside kin selection and self-serving benefits, but we lack an understanding of its importance in natural systems