Behavior

The entiree population shows seasonal movements, occurring in the tropical grasslands of the cerrado from April to September and in the southern upland grasslands from October to March. As other Brazilian seedeaters, migration is associated with thematuration of seeds of grasses and cyperaceous species (Rovedder et al. 2013).

Small flocks of males begin to arrive in the breeding sites on the beginning of November. Females arrive about five to seven days after males and the birds start to pair. Flocks of both males and females continue to arrive until the middle or end of November. Males have natal philopatry and seem to have most site fidelity than females. Most males show fidelity to the same territories year after year (Rovedder 2011).

Many individuals of Black-bellied and other species of seedeaters that are found in the same region share feeding sites located up to about 1.5 km apart from their breeding territories. Such behavior is mainly observed when a large concentration of seeds, mostly one or two species of grass, or other food item is temporally available at a patch far from the breeding territory, indicating that the foraging area can be separate from  the breeding territories and is linked to food availability (Rovedder 2011).

Males of S. melanogaster generally establish their reproductive territories in
wetlands (Bencke et al. 2003), or in the driest portions of steepfields near drainages or wetlands. The latter situation show irregular patterns at successive breeding seasons and depend on optimal conditions, i.e. burned fields and absence of cattle. The territories are not choosen at random, but instead are asssociated with plant composition. Some plant species often found in breeding territories are Eleocharis nudipes and Fimbristylis autumnalis (Cyperaceae) (Rovedder 2011). The mean size of reproductive territories is 0.27 ± 0.03 ha (0.21 to 0.32 ha; n = 23) (Rovedder 2011).

Social monogamy. Males defend their breeding territories against other males by staying in higher natural poles of the vegetation, usually at Eryngium inflorescence, singing and fighting if necessary. During breeding, females remain concealed within vegetation, while the male remains more visible and uses contact calls to the female, always following it close behind. Females are responsible for nest construction and incubation. Nests are preferably not placed where the grasslands have been burnt before birds’ arrival from overwintering areas, but instead nests are placed at the edge of bogs. Both males and females raise two nestlings. In normal conditions, males start to care of nestlings after four to five days of hatching. Social monogamy can be observed for one breeding season and change pairs can occur during the same breeding season for different reasons such as dead or disappearance of one mate (Rovedder and Fontana in preparation).

Forms pairs during the breeding season. During migration and the nonbreeding season, can form intra and/or interspecific flocks with other species of Sporophila. Nestling parasitism by fly larvae (Phylornis sp.) can occurs on occasion. Nesting parasitism by Shiny Cowbird (Molothrus bonariensis) was not detected in three areas in Rio Grande do Sul (2) and Santa Catarina states (1) (Rovedder 2011).

Predation is the major cause of unsuccessful breeding. Potential predators observed frequently at breeding sites are mammals (Pseudalopex gymnocercus, rodents), lizards (Tupinambis merianae), snakes, and birds. Ants have been observed eating eggs, probably after a bird attempt to predate it, breaking the shell. Cattle trampling also can cause nest losses (Rovedder 2011).