Square-tailed Saw-wing Psalidoprocne nitens in the Democratic Republic of the Congo: identity and taxonomic status

Abstract

Summary. The race centralis Neumann, 1904, of Square-tailed Saw-wing Psalidoprocne nitens is currently considered both to be poorly differentiated morphologically from the nominate subspecies and restricted to a limited area of north-eastern Democratic Republic of the Congo, being replaced elsewhere in the country by nominate nitens. Such views are mistaken. Study of specimens confirms assessments of earlier publications, in Dutch and French, that centralis occurs throughout the forest zone of northern and central DR Congo—to which region it is confined—whereas the nominate is known only from the coastal far west of the country. Moreover, the plumage of centralis is glossy dark bottle green, whereas that of nominate nitens is blackish with a dull oily green gloss. This difference was the justification for the initial recognition of centralis but has been almost entirely overlooked since the publication of the original description. Combined with the commonly reported contrast in throat colour and a previously unrecorded difference between the plumages of immatures, centralis is hence more distinct morphologically than previously appreciated. Further, a recent genetic analysis, involving samples from specimens shown by this study to have been centralis, demonstrated a divergence of c.4% from nominate nitens. In combination, these findings argue for the elevation of centralis to species rank.