Throughout much of recorded history, people have been fascinated by the intricate and often brightly-colored patterns displayed by birds. In recent years, evolutionary biologists have reconsidered the importance that mate choice can have in causing the evolution of these patterns. In this project the PIs will investigate two types of mate preferences ("adaptive" and "aesthetic") that may lead to bright coloration and the commonly observed tendency for males to be more brightly colored than females. Female animals (and sometimes males) are often thought to choose their mates based on adaptive traits such as state of health or the ability to be good parents; possibly bright coloration may be indicative of mating quality. In addition, it has been suggested since Darwin's time the female birds have aesthetic mate preferences, preferring "good-looking" males that in turn produce "good-looking" sons. In this research the PIs will use the zebra finch, a small bird native to Australia, to study the significance of sex differences in beak color (males' beaks are redder than females') and preferences for beak color. Females prefer to mate with males with very red beaks. Experiments will be performed to determine if beak color is an adaptive or aesthetic criterion of mate choice. For example, do males with the most red beaks make better fathers? Do their offspring grow at faster rates? Males do not prefer females with red beaks, although females with red beaks do occur both in nature and the lab. The investigators will explore the possibility that this results from genetic constraints that may cause female beaks to evolve to be redder than optimal and male beaks to be less red than optimal. The long-term goal is to elucidate the components of mate choice for animals in general and to understand how mate choice influences evolution species' appearance.
