Eastern Long-tailed Hornbill Horizocerus cassini is split from White-crested (now Western Long-tailed) Hornbill H. albocristatus (Clements 2007:229)

Summary: The forests of western Africa now have another endemic species, the Western Long-tailed Hornbill, distinguished from Eastern Long-tailed Hornbill by its more extensively white head and lack of white wing spots.

Details: Although morphologically strikingly distinct from H. albocristatus in several characters (summarized in del Hoyo and Collar 2014), H. cassini was not recognized to science until Finsch (1903) carried out a detailed comparative study. Nevertheless, they were long treated as conspecific (e.g., Peters 1945, Wolters 1976) until split by del Hoyo and Collar (2014). Of the three taxa united in H. albocristatus, the two most dissimilar in multiple respects (macrourus and cassini) appear to be essentially parapatric, and hence the two-species treatment advocated by HBW and BirdLife International (2022) is adopted by WGAC and followed by Clements et al. (2023).

English names: The previously used English name for the parent species in the eBird/Clements Checklist was White-crested Hornbill, but for alignment with HBW and BirdLife International (2022) the eBird/Clements Checklist now uses the equally apt daughter species names Eastern Long-tailed Hornbill for H. cassini and Western Long-tailed Hornbill for H. albocristatus.