Genetic sequencing shows just how similar these species are. Only 12 of their genes differ―less than 0.1% of their genomes.Intriguingly, one of the 12 is part of one of the sex chromosomes, hinting at a role for sexual selection.Another three of them play a role in the colouration of male plumage, which is also suggestive.For, although the species are of similar sizes and shapes, adult male tawny-bellied seedeaters, as their name implies, have brownish-orange chests, while male Ibera seedeaters have black throats and sandy-coloured bodies.Their songs are distinct, too. They use the same range of frequencies, but different syllables.First, Ms Turbeck and her colleagues established that females of both species did, indeed, regularly select the right mates.Observation of pairs suggested so, and genetic testing of young (needed because more than half the females under study mated with extra males in addition to their long-term partners) did not find any exceptions, either.That done, they looked at males' abilities to distinguish conspecific rivals from heterospecific neutrals.During the 2019 breeding season they mounted decoy males in the territories of 40 male tawny-bellied seedeaters and 36 male Ibera seedeaters.They then monitored the residents' responses when a female was around.They used four decoys. One had the plumage and song of a male Ibera seedeater. One similarly resembled a male tawny-bellied seedeater.
