More partners give healthier offspring.
Individual variation in polygamous mating systems. The overwhelming majority of birds in the populations are individually marked. Polymorphism in MHC, viability, and the evolution of mate choice in natural populations. MHC governs, among other things, vital mechanisms in the antibody-mediated immune response . There are accumulating evidence that different MHC-genotypes induces resistance or susceptibility of several diseases in both mammals and birds.