Why the world's most common owl genus spent a century in taxonomic confusion

Nature · Published 3 October 2026 Swipe more like this →

In short: Scops owls are masters of camouflage, but their evolutionary history has been anything but clear. For decades, scientists struggled to distinguish these Old World birds from their New World screech owl cousins. Only modern DNA analysis finally resolved a long-standing debate over how these cryptic, whistling predators are truly related.

The genus Otus, introduced by Thomas Pennant in 1769, represents the largest group of owls, containing 58 extant species. These compact birds are restricted to the Old World, where their brownish plumage allows them to blend seamlessly into tree bark. While they are often polymorphic, appearing in greyish or reddish-brown morphs, their most defining characteristic is a distinct vocalization: a series of whistles or high-pitched hoots delivered at a rate of fewer than four notes per second.

Taxonomic classification of these birds has been volatile. Throughout the mid-19th century, various groups were split into distinct genera, such as Megascops for screech owls and Ptilopsis for white-faced owls. However, the early 20th century saw a trend toward lumping these taxa back into Otus. This treatment remained dominant until 1999, when mtDNA cytochrome b sequence data suggested that the lumping was unsustainable. By 2003, the American Ornithologists' Union formally re-accepted Megascops as a separate genus, confirming that scops and screech owls are sister lineages that evolved in allopatry.

The evolutionary history of the group remains difficult to map because they have conserved their ecomorphology for millions of years. Fossils from the Late Pliocene of Kansas and Mallorca show that these lineages were already established long ago. Because they are osteologically similar, researchers rely heavily on vocalizations to identify species. Indeed, the discovery of new taxa, such as the Serendib scops owl, often begins with experts hearing unfamiliar calls in the field, highlighting how much remains to be learned about these solitary, cavity-nesting birds.

The importance of these distinctions extends to conservation, as the fossil record often misidentified species. For instance, subfossil material once attributed to tuftless owls was later corrected to the extinct Mauritius owl. Today, the genus continues to grow, with new species like Otus bikegila being formally described as recently as 2022, proving that even in well-studied groups, nature still holds secrets.

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