Cooperation, Conflict and the Evolution of Social Signals

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Striking ornamental traits such as colorful bird plumage are often viewed as synonymous with sexual selection. The bizarre chicks of the American coot, resplendent with their bright orange plumage of modified feathers and a head capped with colorful naked skin, challenge us to consider ornamental signals in a broader evolutionary context. Previous research revealed that parental choice (parental favoritism for particular offspring characteristics) provides extremely strong natural selection for ornamented offspring in American coots and raised a fundamental question: why do parents prefer ornamented offspring? The proposed research will answer this question by investigating how the chick signals function (i.e., their effects on parental behavior), and the consequences of these effects on the reproductive success of the parents (i.e., the number and quality of offspring produced). Both cooperation and conflict can shape the evolution of social signaling systems - determining the relative importance of each remains an important challenge for evolutionary biologists and is a major focus of the proposed research. Experimental manipulation of chick signals (e.g. plumage color, bill color, and skin color) will be used to determine both the mechanism of chick signal function and the consequences to parents and offspring. A two-factor experiment will be conducted to investigate the interaction between chick signals and parental tactics central to food allocation (degree of hatching asynchrony, the main determinant of offspring competitive asymmetries). The research will provide a comprehensive understanding of the evolution of a social signaling system by exploring how natural selection shapes both the signaler and the receiver, and how these fitness consequences interact to produce an integrated social system. While pursuing these research objectives, this project will also provide intensive mentoring of undergraduate students. Nine students will be involved in all aspects of the research program - from planning the field season, to setting up field experiments, to making behavioral observation and data management and analysis - and will gain hands-on experience with a scientific investigation.