Chilean populations of Common Diuca-Finch breed between September and February and may have multiple broods (Bullock 1940). In Argentina, the breeding season extends from November to January, and these birds only have one brood. The nest is an open cup consisting of thorny Acacia and Trevoa sticks, dry grass, and vegetable fibers, often lined with soft vegetation, wool, horsehair, rabbit hair, or other bird feathers (Lazo and Anabalón 1991, Marin 2011). Common Diuca-Finch also uses old nests of other birds, such as Short-billed Canastero (Asthenes baeri) and other species of Furnariidae (Mezquida 2003). The mean nest height above the ground is 1.64 m (range 0.4-4.0 m) (Marin 2011). The nest has a mean internal diameter of 71.5 mm (range 64-78 mm) (Marin 2011). The nest commonly is in an Acacia caven, but also can be placed in bushes, dense thornless trees, or conspicuously in thorny trees with little foliage but constructed with thorny twigs (Marin 2011). It tends to prefer sites that are thornless but with high leaf density, perhaps for camouflage against predators. Alternatively, thorny settings also potentially could protect against predation (Lazo and Anabalón 1991). The clutch usually consists of 2-4 eggs, with a mean of 3 eggs (Lazo and Anabalón 1991, Jaramillo 2011, Marin 2011). Egg coloration is greatly variable, with a base of pale blue to pale glossy green, which is overlayed with densely mottled dark brown, lavender gray, and olive green spots (Marin 2011). The spotting may vary from streaky to so dense that the green is barely visible (Ogilvie-Grant 1912, Marin 2011, Jaramillo 2011). Egg measurements are given in Table 3 below. The incubation period lasts 13-14 days and both parents participate (Marin 2011). At hatching, body mass is about 2.7 g, and nestlings do not exceed 29.5 g in mass. Nestlings fledge 9-10 days after hatching (Marin 2011). Diuca diuca nests are frequently parasitized by Shiny Cowbird (Molothrus bonariensis), a species that expanded into Chile from Argentina in the 1800s (Jaksić 1998, Marin 2011, Jaramillo 2011).