Coua cristata maxima—species or subspecies, adult or juvenile, extant or extinct, aberrant or hybrid?

Coua cristata maxima, known by nothing more than a unique specimen taken in south-east Madagascar in 1948, was distinguished by its greater size than other subspecies of Crested Coua C. cristata (of which pyropyga, sometimes accorded species rank, is the largest) and by its shorter crest, bluer upperparts, wings and tail, fully cinnamon-tawny underparts and mid-sized white tail tips. A separate assessment of the holotype published in 1997 made various refinements to this diagnosis, and our own examination found the facial configuration seemingly inconsistent with that of pyropyga, showing a weaker superciliary line and possibly a reduced area of bare skin around the eye, although these features may, like the short crest, simply be indications of immaturity. Even if they are, however, maxima appears too distinct to retain subspecific rank: it seems more likely to be either a full species or, as first intimated in 1997, a hybrid. Four of the six Coua species around the type locality cannot be possible parents, but seven features of the holotype are consistent with a Blue Coua C. caerulea × C. cristata pairing. Molecular investigation is urgently needed to determine whether maxima is a valid species. If it is, it will either be highly threatened or extinct; little-known hinterland forest from Manafiafy (35 km north-east of Taolagnaro) north at least to Manantenina has been identified for survey.

Three of the world's four main avian checklists, two recent monographs of the Cuculiformes (Payne 2005, Erritzøe et al. 2012) and a handbook to the birds of the Malagasy region (Safford & Hawkins 2013) all treat the Crested Coua Coua cristata of Madagascar as consisting of four subspecies, arranged anti-clockwise as nominate cristata in the east, north and north-west, dumonti in the centre-west, pyropyga in the south-west and south, and maxima in the south-east (Dickinson & Remsen 2013, Clements et al. 2023, Gill et al. 2024). The fourth list splits pyropyga as Chestnut-vented Coua but treats the remaining three subspecies as conspecific (del Hoyo & Collar 2014, HBW & BirdLife International 2024). It is certainly the case that pyropyga is well differentiated from nominate cristata and subspecies dumonti (these two latter being very similar to each other, to the point where we speculate if they might form components of a cline), but it is the taxon maxima that in several ways is the most distinctive of the four. However, this last is known from a single specimen, which inevitably reduces the confidence with which a defensible position on its taxonomic status can be taken. Consequently it has been left as an unaddressed issue for many years, with checklists quietly parking it until further light can be shed. Here we attempt to provide a little more context and clarity to this interesting case, prior to and preparatory for the obviously needed step of a molecular analysis.