Competition for mates is one of the essential characteristics of all sexual reproducing organisms. Sexual selection is particularly strong in males. In some species males have developed several mating strategies to compete for females. Until now the identification of the underlying genetic variation of these alternative strategies has remained largely elusive. Here I propose to identify and study the genes responsible for the three different male phenotypes in the ruff Philomachus pugnax. This shorebird provides a model system for sexual selection that already fascinated Charles Darwin. In ruffs three male morphs are known that differ in morphology, plumage and behaviour: 1) Independent territorial males, the most frequent phenotype, which compete for preferred locations in lek arenas, 2) Satellite males, that form alliances with territorial males for matings, 3) Faeder males that appear very similar to females and mate secretly with females in lek arenas. Previous studies have suggested that the male morphs are under oligogenetic control, regulated by one or, at most two loci. This is because their inheritance follows a simple Mendelian mechanism involving dominant and recessive alleles. I will use next generation sequencing to screen genomic libraries of several thousand genetic markers to test the hypothesis that one or two loci are coding the different male morphs in the ruff. For this I will use a large pedigree of a well-studied captive ruff population that was founded in 1985 and includes 381 individuals. Using available bird genome sequences I will first determine the approximate genomic location(s) of the candidate gene(s) through a combined approach of genome wide association study and linkage mapping. Finally, I will use fine scale mapping with single nucleotide polymorphism markers in a large sample of individuals to determine the exact sequence differences that lead to the three different male morphs in ruffs.