Scaly-breasted Kingfisher (Plain-backed)

Plain-backed Kingfisher Actenoides regalis was considered as distinct species by the HBW/BirdLife Taxonomic Checklist when version 1 of the Lost Birds was launched in 2022. As of 2023, however, Plain-backed Kingfisher is considered to be a subspecies of Scaly-breasted Kingfisher Actenoides princeps in both the HBW/BirdLife Taxonomic Checklist and eBird/Clements global bird taxonomies (see Taxonomy below). The subspecies remains lost, however, and with more data perhaps the Plain-backed Kingfisher could be considered a distinct species again.

Found only in the mountains of southeastern Sulawesi, Indonesia, this subspecies was last documented in 1931.

Known from only two specimens, both of which were collected in December 1931 (AMNH 299296 and this one) from the Mekongga Mountains of southeastern Sulawesi, Indonesia.

Plain-backed Kingfisher is currently considered to be a subspecies of Scaly-breasted Kingfisher Actenoides princeps. The kingfisher was split as a distinct species by del Hoyo and Collar in 2014 and considered a distinct species in the HBW/BirdLife Taxonomic Checklist until 2023 when it was again lumped with Scaly-breasted Kingfisher in v8.1 of the HBW/BirdLife Taxonomic Checklist. As a result, the Plain-backed Kingfisher was considered as lost species in version 1 of the Lost Birds list (published in 2022).

In the eBird/Clements global taxonomy, Plain-backed Kingfisher is also considered a subspecies and listed in the eBird database as Scaly-breasted Kingfisher (Plain-backed). Given how little is known about this bird, however, is does not seem impossible that a rediscovery and updated information on the kingfisher's vocalizations and morphology could once again change how it is treated taxonomically.

It is worth noting that is also an undescribed taxon of Scaly-breasted Kingfisher, which was observed on Mount Tumpu in eastern Sulawesi in January 2014 (Rheindt et al. 2014). A better understanding of the status of this undescribed population could help clarify the status of Plain-backed Kingfisher as well.