The sociable weaver is a small species of bird that lives in South Africa and that scientists have studied as a model for understanding cooperation. These weavers work together to build large, communal nests, to cooperatively raise young and to mob predators. Scientists have collected long-term data about sociable weavers to try and understand the dynamics driving cooperative behaviour in the species and its evolutionary basis. This will inform our understanding of cooperative behaviour in other species, including humans. The EU-funded COOPERATION (Towards an understanding of cooperation in an African passerine bird) initiative used a multidisciplinary approach to investigate the costs and benefits of cooperation in the sociable weaver. They did this by integrating long-term field data, genetics and physiology to obtain comprehensive estimates of individual fitness. This initiative represents the continuation of a long-term study with data from as far back as 1993. The researchers looked at various aspects of cooperation costs and benefits and how they impact population dynamics – that is, the population’s size and age composition. One of the topics they investigated was cryptic helper effects, which refers to the benefits provided by helpers that go beyond improving breeding success. Helpers are the birds that do not breed themselves, but help other birds to breed. The scientists found that females breeding with helpers produce smaller eggs, which benefits the breeding females but doesn't impact their offspring. This evidence supports the hypothesis of cryptic helper effects. COOPERATION brought together a large team of 21 researchers and students with expertise in different fields from France, Portugal, South Africa and the United Kingdom. This collaboration facilitated the exchange of knowledge and led to a substantial consolidation of research and a marked increase in productivity. Students in particular benefited from the sharing of skills and knowledge. These research findings have advanced our understanding of sociality and produced insights into understanding the evolution of cooperation and its effects at the population level.
Cooperation, sociable weaver, cooperative behaviour, population dynamics, cryptic helper effects