Male at attractiveness and differential testosterone investment in zebra finch eggs

Good-genes hypotheses of sexual selection predict that offspring fathered b y preferred males should have increased viability resulting from superior g enetic quality. Several studies of birds have reported findings consistent with this prediction, but maternal effects are an important confounding var iable. Those studies that have attempted to control for maternal effects ha ve only considered differential maternal investment after egg laying. Howev er, female birds differentially deposit testosterone in the eggs, and this influences the development of the chick. This study shows that female birds deposit higher amounts of testosterone and 5 alpha-dihydrotestosterone in their eggs when mated to more attractive males.