Nest is built from dry grasses and twigs placed in a branch of an isolated bush or small tree overhanging water. There is often a threat of nest destruction in Amazonian watersheds if water levels rise drastically (Jaramillo 2011). A single nest discovered in Laguna Grande of the Cuyabeno Faunistic Reserve of north-east Ecuador in August of 2003, with three eggs nested 30 cm above water in the roots of a Macrolobium tree (Greeney and Merino 2007). The nest had an open-cup shape and was composed of rootlets and twigs. The nest measured 9.5 cm wide by 7 cm tall outside, and 7 cm wide inside by 4 cm deep. The average measurements of the eggs were 21.6 ± 0.5 mm by 16.0 ± 0.1 mm (Greeney and Merino 2007). A clutch is commonly 2 eggs. Eggs are off-white with spots of sepia and dark brown (Jaramillo 2011). The eggs were covered for less than half of the time in intervals averaging 10 ± 6 min (Greeney and Merino 2007).
There is a threat of brood parasitism by the Argentine Shiny Cowbird, Molothrus bonariensis bonariensis. Three sets of Red-capped Cardinal eggs have been identified with evidence of brood parasitism by the Argentine Shiny Cowbird in Brazil during November of 1926. These nests each contained one Argentine Shin Cowbird egg and one to three Red-capped Cardinal eggs (Friedmann 1949).