Top: a "resident" father mated with three females produced the male offspring illustrated below each mother. All these sons behave as residents, as expected from their dark head tufts.

Bottom: Sons from a satellite male mated with three females. Those with dark ruffs or head tufts are residents, while those with light or golden head tufts are satellites.

Data in the paper published in Nature support a "single locus" genetic model in which a satellite "allele" is dominant to a resident "allele". These "alleles" could reflect alternative sets of loci maintained in linkage disequilibrium by a chromosomal inversion polymorphism, as occurs in the polymorphic white-throated sparrow, or actually result from differences at a single locus.