The most speciose genus (a group of closely related species) of owls in South America is Megascops, popularly known as screech-owls. About 20 of these species are spread over most of the continent and have very similar plumage. This makes determining how many species there are difficult, and it is possible there are more species than previously thought. 

A recent genetic study by Sidnei Dantas and collaborators, in a collaboration between the Museu Paraense Emilio Goeldi in Brazil, and institutions in USA, Colombia and Denmark, suggests that distinct populations of many Megascops may be separate species. This hidden diversity was suspected before genetic data, despite the plumage similarities between the populations. Why? Through differences in the songs between these populations, observed in many species. Thus recognizing differences in songs from populations of the southern tawny-bellied screech-owl (Megascops ustain Brazilian Amazonia led to our study, a taxonomic review of that and two other species, the tawny-bellied screech-owl (Megascops watsonii), also Amazonian, and the black-capped screech-owl (Megascops atricapilla), from the Atlantic forest. Although these species are closely related, prior studies had suggested more species could be involved. And what we found by the end of the study is that the number of species was twice what was previously thought!

In our study, we first looked for genetic differences between populations with distinct songs, and the degree of difference between them. To do this, we extracted DNA from muscular tissue from individuals of the three species. This study would not have been possible without specimens collected on scientific expeditions and housed in biological collections . These specimens allow us to advance research and generate new knowledge. 

Our analysis revealed six distinct genetic groups, each one in a different region of Amazonia or Atlantic Forest (see the figure below). Then, we identified differences in morphology (size and coloration) and in the vocalization of the owls, that could distinguish between these six genetic groups. The morphological examination did not reveal many differences between populations both because the populations themselves had similar morphologies, but also because within a single population there was a wide range of individual variation. For example, it is possible to find five or more color patterns in the same population, what makes creating a general description a big headache. However, vocalizations were more useful to tell populations apart, even though many of them have similar songs.