Mesopotamia is a low-lying region covering Misiones, Corrientes and Entre Ríos provinces of north-west Argentina. The EBA is restricted to the two southernmost provinces of Mesopotamia, covering much of Corrientes and eastern Entre Ríos, along the floodplains of the lower Uruguay river to where it enters the Río de la Plata in the Paraná delta. Also included in the EBA is western and south-east Uruguay and southern Rio Grande do Sul state in Brazil. The EBA probably also extends into extreme southern Paraguay as two of the restricted-range birds have been found recently during the breeding season (R. P. Clay in litt. 1997). The principal habitat is marshes and periodically inundated wet grassland, which are interspersed in a mosaic of other habitats, especially spiny woodland ('espinal'), gallery forest and large bodies of standing water ('esteros').

The three restricted-range species are in the genus Sporophila, all breeding in periodically inundated grassland and marsh, especially those supporting tall, dense grasses (especially Paspalum), often with isolated bushes (including Acacia caven and Solanum glaucophyllum) and herbaceous plants such as Eryngium (Pearman and Abadie in press). They are all austral migrants, wintering north of the EBA mainly in the pantanal of central Brazil, birds on migration having been recorded in Paraguay and other parts of Brazil.

The three species are patchily distributed within their breeding ranges. They all overlap only in eastern Entre Ríos province, where 0.04> Sporophila zelichi is known from only two adjacent breeding localities (Collar et al. 1992, Pearman and Abadie in press). S. cinnamomea is found mainly in central and south-east Corrientes and scattered locally in eastern Entre Ríos, with single records over the border in Rio Grande do Sul in Brazil (Belton 1984–1985) and now recent records from Artigas, Salto Paysandú, Río Negro and Soriano departments in western Uruguay and Trenta y Tres and Rocha departments in eastern Uruguay (A. Aspiroz in litt. 1997). S. palustris is spread more widely through the EBA, but eastern Entre Ríos is its main breeding area; also Rocha department in eastern Uruguay is now thought to be important for the species (A. Aspiroz in litt. 1997). There are also a handful of historical records from Rio Grande do Sul in Brazil. It has also probably bred further south in the Paraná delta but these records could possibly refer to escaped cage-birds (M. Pearman in litt. 1996).

The taxonomic status of S. zelichi (described as recently as 1977) is controversial owing to its clear morphological affinities with other species in the genus. A recent study conducted in 1991-1993 found it always to breed in close association with S. palustris, and concluded through preliminary DNA work that the bird represents a distinct colour morph of palustris. The situation is still more complicated than this, however, for the affinities of palustris are unclear, Pearman and Abadie (in press) having suggested that it is probably conspecific with southern populations of Rufous-rumped Seedeater S. hypochroma, a widespread species which occurs in western Corrientes, Bolivia, Brazil and probably Paraguay. For the moment, all three taxa are recognized as separate species (e.g. Ridgely and Tudor 1989, Sibley and Monroe 1991, Collar et al. 1992, Stotz et al. 1996), but there is a clear need for a taxonomic review that incorporates not only morphology but song, breeding ecology and genetics.

Much of the land within this EBA is under agricultural production, especially for cattle-ranching in Corrientes. Degradation of grassland through overgrazing and trampling is a common problem, while drainage of marshes and the burning of stands of tall natural grasses pose additional threats to the area. A recent development is afforestation projects mainly of Eucalyptus and pine, with greatest interest focused on eastern Entre Ríos and north-east Corrientes (Collar et al. 1992, Pearman and Abadie in press).

Two of the species, Sporophila zelichi and S. palustris, are considered threatened, not only owing to destruction of their breeding habitat, but also because the males are popular cage-birds; heavy trapping pressure has led to serious declines in their populations. Several widespread threatened birds also occur in the EBA, including Crowned Eagle Harpyhaliaetus coronatus (classified as Vulnerable), Speckled Crake Coturnicops notatus (Data Deficient), Sickle-winged Nightjar Eleothreptus anomalus (Near Threatened), Strange-tailed Tyrant Yetapa risora (Vulnerable), Ochre-breasted Pipit Anthus nattereri (Endangered), Black-and-white Monjita Heteroxolmis dominicana (Vulnerable), Yellow Cardinal Gubernatrix cristata (Endangered), Saffron-cowled Blackbird Xanthopsar flavus (Endangered) and Pampas Meadowlark Sturnella militaris (Endangered). Moreover, the EBA is undoubtedly the most important region for several of these species, especially Y. risora, A. nattereri, and X. flavus (Wege and Long 1995, Pearman and Abadie in press), and so the conservation of the grassland there is crucial.

Eight Key Areas for threatened birds have been identified within this EBA (Wege and Long 1995): five in Argentina (Caza Pava and Colonia Carlos Pellegrini in Corrientes, and Selva de Montiel, El Palmar National Park and Gualeguaychú in Entre Ríos) and three in Uruguay (El Rosario in Río Negro, and Bañados de India Muerta, Bañados de Santa Teresa and Los Indios in Rocha). Of these, Colonia Carlos Pellegrini (holding eight threatened species) and Gualeguaychú (with seven threatened species and all the restricted-range species) are the two most important sites, and both are in need of better protection (Pearman and Abadie in press).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Argentine Mesopotamian grasslands. Downloaded from https://datazone.birdlife.org/eba/factsheet/73 on 22/11/2024.