In birds, much work on sociality and cooperation has been devoted to understand the evolution of cooperative breeding, where conspecifics raise others offspring. This costly form of cooperation evolved widespread, but the factors favouring its evolution remain debated. Our research resolved this debate by using comparative work based on 3000 bird species, demonstrating that family living is an essential steppingstone in the evolution of cooperative breeding. The steppingstone model clarifies previous disagreements regarding the evolutionary drivers of cooperative breeding, and provide a unifying framework to understand its evolution.
We are using Siberian jays to explore the hormones that are associated with social relationships among group members, using field experiments. This work is ongoing so keep an eye open for preprints and exciting results.
We study the family-living, non-cooperatively breeding Siberian jays to investigate the adaptive benefits of family living. In addition to a breeding pair, groups can include offspring that remain up to 4 years with their parents, and unrelated non-breeders, allowing us to assess the benefits of family living. Experiments demonstrated that parents provide their offspring with access to food and protection from predators. Also, parents provide their offspring with opportunities to learn vital skills, e.g., recognizing predators, boosting their survival and lifetime reproductive success. Thus, family living is highly adaptive, providing offspring a safe haven to learn vital skills.
Large brains are very beneficial because they are the foundation of cognitive adaptations, but they require a constant energy supply at a high rate, particularly during growth when young still lack the ability to feed themselves. To address this seemingly insurmountable energetic constraint, we conceived the parental provisioning hypothesis, proposing that energetic inputs by parents (via egg size, feeding and keeping the young warm), is a precondition for the evolution of large brains. Comparative analyses in over 1150 bird species confirmed that parental provisioning strongly predicts variation in relative brain size. Similar patterns are observed in other vertebrates, suggesting that these two traits coevolved. These results cast doubt on the explanatory value of previously considered social or technological cognitive abilities, suggesting we rethink our approach to cognitive evolution.
Language is a defining feature of humans, but given its uniqueness, it is challenging to study the factors that ultimately drove its evolution. The power of language arises from our ability to combine meaningless vocal elements (phonemes) into words, which in turn are combined into meaningful phrases based on grammatical rules (syntax). Our research demonstrated that Siberian jays evolved functionally referential calls that designate predator category and predator behaviour. Collaborative research (PI Dr Toshitaka Suzuki, The University of Tokyo) highlighted that on Japanese tits evolved syntactic combinations, where the meaning is determined by its constituent parts and how they are combined. This work is the first demonstration of syntax in an animal. Thus, language-like features also evolved in birds, advancing our understanding of animal linguistics.
Siberian jays live all winter of hoarded food. Thus, the species depends on cold winter without warm spells. Population models show that our study population in pristine boreal forests are more resilient to disturbances that our study population in managed forests. Populations in managed forests are therefore also less resilient to the effects of climate change. We have an ongoing dialogue with forest companies to share our insights with key stakeholders.