Phenotypic Discrimination of the Andean Ibis (Theristicus branickii)

Many authors do not recognize the highland Andean Ibis (Theristicus branickii) as a species distinct from lowland Black-faced Ibis (T. melanopis). We considered this problem using a new system of quantitative criteria for species
recognition. Andean Ibis differs from Black-faced Ibis markedly in proportions (shorter bill: mean 118 vs. 140 mm; longer tail: mean 215 vs. 185 mm), structure (no wattle), and color pattern (rufous-chestnut crown, face and nape rather than rufous-chestnut crown only; larger white vs. smaller rusty-buff belly-patch). We propose elevation of Andean Ibis to full species. It is rare in Ecuador and Bolivia, vagrant in Chile and only likely to be moderately abundant in Peru.