In mate competition, both sexes need credible signals: males must signal fitness (health, resources, genetic quality), females must signal fertility (age, health, reproductive capacity). Yet both sexes have incentive to fake these signals—to appear more fit or fertile than they actually are.1
Courtship displays solve this through costly signaling: displays that are expensive to produce and thus reliable indicators of underlying quality. A sickly male cannot afford to display vigorously; a healthy male can.2
Males typically display dominance, resources, and commitment through behavioral signals: confidence, status displays, willingness to invest. Females typically display fertility and health through physical signals: symmetry, health indicators, age-linked markers.3
These differences reflect differential parental investment: males compete primarily through status/resources; females select for males who can and will invest. The displays target what matters for mating success in each sex.4