From Bird Guides

A nearly two-century-old taxonomic mystery has finally been resolved, with Southern Spectacled Owl - long considered a subspecies of Spectacled Owl - now recognised as a distinct species, according to a newly published review.

Spectacled Owl is a large, nocturnal forest raptor found from southern Mexico through much of tropical South America. For decades, ornithologists have debated the status of the pulsatrix subspecies, which differs in plumage and vocalsiations from other populations of the widespread species. Although originally described almost 200 years ago, conflicting interpretations of morphology and limited comparative data left its taxonomic position unresolved.

A recent study revisited this question, combining genetic analyses, detailed comparisons of plumage and measurements and an evaluation of vocalisations across the group's range.

The results showed that pulsatrix differs significantly and consistently from other Spectacled Owl populations - enough to merit full species status under modern taxonomic criteria.

Under the revised treatment, Pulsatrix pulsatrix should now be considered a separate species. The taxon is native to south-eastern Brazil, from about Bahia south to Rio Grande do Sul in the area of Aparados da Serra National Park, and also bordering over into north-eastern Argentina.

The elevation of pulsatrix to full species status has implications for conservation and research. Species classification can influence how populations are monitored and prioritised, particularly in regions where habitat loss and fragmentation threaten forest-dependent birds. Clarifying species limits helps refine assessments of distribution, population size and trends - essential information for effective conservation planning. A recent study revisited this question, combining genetic analyses, detailed comparisons of plumage and measurements and an evaluation of vocalisations across the group's range.

More info in comments. It's all written in technical language, so I don't want it to get overwhelming.