The Tiger-Herons (Tigrisoma) of Argentina

Abstract

The tiger-herons (Tigrisoma) known from Argentina are reviewed and their relationships, diagnostic features, and known ranges are indicated. Tigrisoma fasciatum (Such) is shown not to be a subspecies of Tigrisoma lineatum (Boddaert), (as treated in "Catalogue of Birds of the Americas"), but is a close ally of T. salmoni and pallescens, with which it is here regarded as conspecific. The specific binomen of the complex becomes T. fasciatum, as the earliest name. The species T. fasciatum "Hocó oscuro" (including its three races, fasciatum, salmoni and pallescens) differs from the species T. lineatum "Hocó colorado" (including its two races lineatum and marmoratum) by having in all plumages interscapular powder-downs, and relatively short and stout bill, with somewhat arched culmen; and in definitive adult plumage black crest and crown, slaty sides of head, blackish neck and mandible with narrow buff or rusty barring, widely separated by broad blackish interspaces; and plain slaty flanks. In definitive adult plumage the species T. lineatum has rufous-chestnut head and neck, finely and closely vermiculated blackish and buff mandible, slaty flanks sharply banded with white. The rarity of specimens of T. fasciatum, the failure of the books to describe adequately the diagnostic features of the definitive adult plumage, and the frequent difficulty of separating young birds from young of T. l. marmoratum without checking for interscapular powder-downs (a character first noted by Zotta), have caused many misidentifications. The following races of Tigrisoma are recorded from Argentina: T. lineatum marmoratum (Vieillot), throughout lower elevations in northern Argentina where habitat is suitable, south at least occasionally to Mendoza and Buenos Aires. T. fasciatum fasciatum (Such), known in Argentina from two examples taken at Bonpland, Misiones on the same date; otherwise recorded only from southern (chiefly southeastern) Brazil. T. fasciatum pallescens Olrog, known only from northwestern Argentina in Salta and Tucumán, but probably of wider distribution. The Argentine specimen attributed in the literature to T. salmoni brevirostre Sztolcman are regarded as actually fasciatum (Misiones specimens) or pallescens (Salta specimens); brevirostre is considered a synonym of T. l. salmoni Sclater & Salvin, ranging from Costa Rica and Panama through the mountain slopes of western South America from Colombia and Venezuela to Bolivia. "T. bolivianum (L.Onnberg)", recorded from Corrientes, is regarded as merely a rare black-crowned variant of T. l. marmoratum, with which it agrees in other color characters and in structural features.