Dr. Peter Dunn from our department two years ago coauthored a PNAS aper about differences in sexual selectio in Common Yellowthroat Warblers. Briefly describe the methods how they showed the differences in mating preference in these species between those in New York and Wisconsin and what advantages they confer for the female and the young. How does this stuy complement the study we discussed in class about female barn swallows and other birds and why these traits do not become "fixed" in the species. Explain in terms of what Fisher (1931) Runaway model, Zahari (1978) Handicap principle and Hamilton & Zuk (1982) have proposed for sexual selection in birds.