Doctoral Dissertations

Orcid ID


Date of Award


Degree Type


Degree Name

Doctor of Philosophy



Major Professor

Todd M. Freeberg

Committee Members

Gordon Burghardt, Matthew Cooper, David Buehler, Nina Fefferman


This dissertation assesses fundamental social factors that drive variation in calling and other behaviors of experimental flocks of Carolina chickadees. Specifically, I tested how group member familiarity and group composition affected individual behavior. In addition, I performed a direct experimental test of the Social Complexity Hypothesis for Communicative Complexity, which states that groups that are more socially complex will communicate with greater signal complexity than groups that are less social complex. I consider complexity to be a combination of three factors: the number of parts in a system, the variation among the parts, and the variation in the way those parts interact. In this dissertation I tested for these effects in flocks of Carolina chickadees (and sometime tufted titmice). I trapped birds from naturally occurring wild flocks and experimentally created flocks in semi-natural outdoor aviaries. I used a mix of ad libitum and focal sampling methods to observe and record behaviors of birds in flocks. I then transcribed note types of calls produced by birds to be able to calculate metrics of communicative complexity. Chapter 1 tests for the effect of flockmate familiarity on note composition and information content of calls in flocks of Carolina chickadees. I found that although note-type usage differed between conditions, information content of calls and social group association patterns did not differ. Chapters 2 and 3 examine the effect of species composition of groups on calling, flying, and social behavior of chickadees and titmice. The results of both of these chapters show that chickadees are influenced by both conspecific and heterospecific presence in flocks, while titmice are mostly sensitive to heterospecific presence, except in risk. Chapter 4 is a direct test of the Social Complexity Hypothesis for Communicative Complexity on two axes: group size and group composition. Surprisingly, I found evidence that transition networks of note types in chick-a-dee calls did not differ greatly across different conditions, although structural changes were more apparent in networks that only included notes and transitions that occurred more than 5% of the time. These results may refute predictions made by the social complexity hypothesis for communicative complexity. In sum, chickadees are sensitive to their immediate social environment, which influences various types of individual behavior in these birds. This work is important for understanding how social group context influences the behavior of individuals in those groups. Overall, this dissertation work demonstrates that social group composition and size can influence behavior of individuals in those groups, albeit in different ways for different behavior patterns. Additionally, there may be asymmetries in of how these variables affect different species in mixed-species groups. These results further inform the ways we think about ecology and behavior of individuals in mixed species groups and support the idea that macro-level group structure may differ from how individuals experience the groups of which they are part.

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