The Common Diuca-Finch (Diuca diuca) is a common and distinctive species of tanager found from Patagonia north to southern Bolivia. The Common Diuca-Finch has a complex taxonomic history due to morphological convergence with finch-like birds and other tanagers that have evolved finch-like morphologies. The Common Diuca-Finch is principally gray above, becoming blackish over the wings and tail, with a white throat, contrasting somewhat with the otherwise grayish underparts. It is a generally common constituent of the avifauna in shrublands and cultivated areas, and Patagonian deserts, and perches boldly atop low bushes (Jaramillo 2011).
The Common Diuca-Finch is a distinctive and common bird in its austral range. The Common Diuca-Finch is not likely to be confused in the field because the only two species that resemble it, the White-winged Diuca-Finch (Diuca speculifera) and the White-throated Sierra-Finch (Phrygilus erythronotus), are found in the high Andes while Diuca diuca is only found in lowlands (Ridgely and Tudor 1989). The Common Diuca-Finch has white markings on the tail, which all Phrygilis species lack. The Common Diuca-Finch can be seen walking on the ground, similar to the walk of a quail (Jaramillo 2003, Cueto et al. 2013), while the White-winged Diuca-Finch hops (Jaramillo 2011). The white eye-crescents of the White-winged Diuca-Finch are larger and more pronounced than those of the Common Diuca-Finch. Recent phylogenetic analysis has revealed the Yellow Cardinal (Gubernatrix cristata) as the Common Diuca-Finch’s closest relative (Burns et al. 2014). They have hybridized in the wild, and the hybrid’s morphology is similar to G. cristata while the coloration is more like D. diuca, except for the presence of the black bib characteristic of G. cristata. These hybrids have been seen in the provinces of southern Buenos Aires, La Pampa, and Río Negro (Bertonatti and Guerra 1997).
The Common Diuca-Finch is a medium-sized finch with a plump body. The adults of this familiar and conspicuous species have a dark grey head, back, and sides, which is darkest around the lores (Jaramillo 2011). They have a contrasting white midbelly extending to the chest in an upside down V-shape, leading up to the grey breast-band that borders the large white throat patch. The head features a peaked crown, small, white, lower eyelid crescents, and a stout, black bill with a dark and distinctly curved culmen and a blue-grey lower mandible (Jaramillo 2011). The long, blackish tail has broad white tips extending to the outer retrices, which can be seen best in flight or during frequent but brief spreading of the tail (Sick 1993). The wings are darker grey, almost blackish, on the upperwing coverts and fade to paler grey on the edges. The lower flanks and sides of the crissum have a rufous-cinnamon wash. Some have dull wingbars. The female has a brownish tinge in the grey areas and the flanks are less rusty. The sexes are likely more dichromatic than we can perceive in the UV spectrum, as evidenced when color is measured under a model of avian vision (Burns and Shultz 2012). Diuca diuca’s walking style has been described as similar to that of a quail (Fjeldså and Krabbe 1990, Jaramillo 2003). There are variances among the subspecies; see the geographic variation section for more information. The juvenile is similar to female in coloration, except with a buff instead of rufous vent (Jaramillo 2011).
Tanagers that have been studied have either a Complex Basic Strategy or Complex Alternative Strategy (Ryder and Wolfe 2009). However, most tanagers only molt once a year (Isler and Isler 1987), and this prebasic molt most likely occurs after the breeding season (Isler and Isler 1987, Ryder and Wolfe 2009). Many species have been found to breed in subadult plumage (Isler and Isler 1987). Although a juvenile plumage is described for Diuca diuca (Jaramillo 2011), more specific information on molt and its timing is not available for this species.
Bill is black and stout with a blue-grey lower mandible and a rounded culmen (Sick 1993, Jaramillo 2003, Jaramillo 2011). Irises are brown and legs are brownish-grey to blackish (Jaramillo 2011).
Both sexes are about 16-18 cm in length, most commonly reported as 16-17 cm (Ridgely and Tudor 1989, Sick 1993, Jaramillo 2003, Perlo 2009, Ridgely and Tudor 2009). Both sexes have a mass of about 37 g, with more specific and further measurements in Table 1 below (Egli 1996, Marin 2011). Detailed measurements of nestling growth can also be found in Marin (2011).
Table 1. Standard Measurements
|Reference:||Egli 1996||Marin 2011|
|Weight (g)||36.8||31-41||21||33.7||11 |
|Total length (mm)||167.4||154-181||23||-|| -|
|Wing (mm)||86.5||80-92||23||89.8||26 |