Common Diuca-Finch locomotes by walking, not hopping; the walking style has been described as similar to that of a quail (Jaramillo 2003, Cueto et al. 2013). It begins to sing at break of dawn and also begins foraging on the ground in the morning, and at midday is sometimes found in low shrubs to avoid the heat (Fjeldså and Krabbe 1990, Jaramillo 2011). Usually, Common Diuca-Finch is seen in pairs or family groups as well as in small flocks during the winter non-breeding season (Jaramillo 2011).
There is very little information on territorial defense, maintenance, or fidelity, or for territory or home range size, for Common Diuca-Finch.
Little information; presumably Common Diuca-Finch is at least socially monogamous (see Breeding).
Social and interspecific behavior
Usually, Common Diuca-Finch is in pairs or family groups as well as in small flocks during the winter non-breeding season (Jaramillo 2011).
The egg to fledgling mortality rate of Common Diuca-Finch is 68.3-82%, with 56.% of mortality occurring during the egg state (Lazo and Anabalón 1991, Marin 2011). An observational study of diuca-finch nests frequently found missing eggs and chicks (Lazo and Anabalón 1991). In one instance Chimango Caracara (Milvago chimango) feathers were found in a nest that was missing two eggs. Other confirmed predators of diuca-finch eggs and nestlings are Austral Pygmy-Owl (Glaucidium nana), mouse-opossums (Marmosa elegans), racerunner (Callopistes palluma), and the snake Philodryas chamissonis (Jiménez and Jaksić 1989, Lazo and Anabalón 1991). Nests of the diuca-finch frequently are parasitized by the brood parasite Shiny Cowbird (Molothrus bonariensis); of 72 passerine nests parasitized by the cowbird, fully 61% belonged to the diuca-finch (Johnson 1967). The cowbird also frequently punctures Common Diuca-Finch eggs, leading to mortality (Marin 2011), and the frequent presence of punctured eggs in diuca-finch nests is attributed to this nest parasite (Johnson 1967, King 1973, Marin 2011). Known parasites on nestlings include the subcutaneous larvae of a Philornis sp. (Diptera, Muscidae), which specialize on birds (Mezquida 2003). It also is parasitized by the mite Harpyrhynchoides zumpti (Bochkov and Galloway 2001).