| Cognition shapes the interactions of an animal with its environment. Species vary greatly in all aspects of cognition, and studying the relationship between this variation and ecology is crucial for understanding how intelligence has evolved. In this thesis, I approach questions about the ecology and evolution of cognition that are often ignored because cognition is difficult to quantify. I use innovation rate as an operational measure and residual brain size as a correlate of general cognition in birds. I first examine the link between cognition and ecology through comparative analyses of the relationships between residual brain size, innovativeness, and measures of ecological generalism across a broad sample of the avian phylogeny, and within a single clade (Icteridae). I find that innovation is positively correlated with habitat breadth but not diet generalism, and that neither measure of generalism is associated with residual brain size. Although residual brain size and innovation rate are strongly correlated with one another, they each appear to have different relationships to a species' ecology. Further analysis finds that the relationship between innovativeness and residual brain size is driven by innovations that involve the use of novel foraging techniques and not the ingestion of new food items. Comparative studies use the traits of extant species to infer their evolutionary history, but can only speculate on the forces driving changes in a trait. The latter half of my thesis focuses on these underlying forces and behavioural mechanisms. Using a game theory model, I show that unpredictable food availability might drive both behavioural flexibility and sociality, two traits strongly associated with cognitive complexity. Finally, I focus on innovativeness at the intraspecific level and examine foraging innovation in a large-brained grackle species, Quiscalus lugubris. I find that this gregarious species is slower to innovate when conspecifics are nearby, and that individuals differ in their ability to solve novel problems. I use these differences to describe the process of innovation, and show that novelty responses, attention, persistence, and flexibility are all important factors underlying individual variation in the ability to innovate. |
