The Double-collared Seedeater (Sporophila caerulescens) is the most common seedeater in southern South America. Because information on its breeding biology is mostly limited to descriptions of nests and eggs, I studied the reproductive biology of the Double-collared Seedeater in southeastern Brazil. I found 41 active nests during seven breeding seasons (1997–2003). Nesting occurred from December to May. All nests found during incubation contained two eggs, eggs were laid on consecutive days, and incubation started the morning the female laid the last egg. Incubation and nestling periods were 12 and 12–15 days, respectively. Only females incubated the eggs. Mean time spent incubating/hr was 52.3 min, and incubation recesses averaged 6.6 min. Nestlings were fed 7.6 times/hr, and although both males and females fed the young, the participation of females was significantly greater than that of males. Predation was the major cause of nest failure. Daily survival rates during the incubation (0.990) and nestling (0.935) stages differed. Overall nesting success was 36%. Although studies conducted in disturbed areas can reveal greater rates of nest predation than those found in undisturbed areas, some Sporophila species seem to benefit from habitat disturbance. The conversion of native habitats to agricultural lands in Brazil, as well as the spread of exotic grasses, has resulted in the expansion of the Double-collared Seedeater to previously forested areas.
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Vol. 118 • No. 1