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Abstract

The use of color and movement are foundational aspects of animal visual communication, but the underlying causes of the diversity in color and display behaviors across species remain an outstanding evolutionary question. While traditionally studied in isolation, integrating color and motion to assess the entire visual phenotype is necessary to understand not only the relationship between these two components but to also elucidate what factors may be contributing to the variation observed in the natural world. The focus of this dissertation lies at the nexus of sensory ecology, behavioral ecology and kinematic methods to ask how color and display co-vary and to evaluate the role of the signaling environment in the diversification of both traits. Using field-based methods and a comparative approach, I analyze plumage variation, display behavior and light environment across 13 species of warblers in the Himalaya in the context of intraspecific aggression. In Chapter 2, I investigate the presence and use of a concealed visual signal across bush warblers and allies in the family Cettiidae and find that visual communication in cryptic, otherwise “drab” species may be much more prevalent than is currently appreciated or understood. In Chapter 3, I conduct a comparative study on the use of wing motions during territorial displays across 11 closely related bird species and ask whether species differences may be related to habitat brightness. This chapter provides one of the most detailed analyses on the shape of wing movements sampled from wild individuals and suggests that certain motions used during displays are highly conserved across species and are modified in modular ways. Lastly, in Chapter 4, I turn to evaluate plumage color variation in twelve Phylloscopus species and ask whether color differences can be explained by variation in light environment across habitats and use in display. The results from this chapter suggest that even in a system where color diversity is relatively simple, the influences shaping color diversification remain complex. The work in this dissertation endeavors to expand the scope of the type of species and contexts studied in visual communication by focusing on animals with relatively subtle variation in color and to consider behaviors used during aggressive signaling. By combining field experiments, comparative analyses and natural history collections, this research provides a comprehensive insight into the complicated interplay between color and motion in a group of Himalayan warblers.

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