The breeding season for Red-crested Cardinal is from early October to mid-February (Segura and Arturi 2009). A full cycle from nest construction to last fledgling leaving is an average of 25.8 ± 0.1 days, and breeding pairs stayed together for the duration of the season (Segura et al. in press). Nests were built primarily in C. tala trees surrounded by dense tree cover, and secondarily on Coronillo trees (Scutia buxifolia) and Molle trees (Schinus longifolius) (Segura and Arturi 2009), and while the cardinals preferred Coronillo trees less near the end of the season both nest height and tree cover increased as the season progressed (Segura et al. in press). The microhabitat was found to be nest cover with the majority of leaves and branches covering the nest from above to deter aerial predators, but the cardinals avoided sites too concealed that reduced visibility from the nest of approaching predators. In a study of 106 nests, 64 (60%) were found on the border of the forest chain, 23 (22%) were in small isolated forest patches, and 19 (18%) in the center of the continuous forest chain (Segura et al. 2012).
Nests are open cups constructed of thin branches of tala and small stems of grass while the chamber is lined with thin rootlets, vegetation fibers and cattle hair (Segura and Reboreda 2011). Nests are constructed solely by the males (Pendleton 1996, cited in Lindholm 2003), and are built in small forks of trees 2-6 m off the ground (Segura and Arturi 2009). The external diameter averages 13 cm and the internal diameter averages 6.5 cm, with a depth of 4.5 cm and a wall thickness of 2 cm (Segura and Reboreda 2011). Nest construction takes and average of 6.1±0.4 days (Segura et al. in press).
The eggs of the Red-crested Cardinal are greenish with evenly spread brown marks, though sometimes have more marks or marks of ochre or black (Jaramillo 2011). In 105 nests, the mass of the eggs average 3.80 ± 0.04 g (range 3.0-5.2 g), and have an average length of 25.2 ± 0.12 mm (range 22-28.7 mm) with an average width of 17.2 ± 0.08 mm (range 14.9-19.5 mm), and these dimensions did not vary during the season (Segura et al. in press). The egg laying period in the wild is observed at around 13 days (Segura and Berkunsky 2012), starting roughly 3 days after nest construction (Segura et al. in press), though in captivity one egg can be laid daily (Pendleton 1996, cited in Lindholm 2003). Mean clutch size for 165 nests is 3.09 ± 0.05 eggs, with 70% of nests having three eggs, 11% having two, 18% having four, and 1% having five. Egg survival rate is determined to be 0.95 ± 0.02 (Segura et al. in press).
The female of the pair incubates the eggs (Pendleton 1996, cited in Lindholm 2003), and starts after the second egg is laid (Segura and Reboreda 2012a). Incubation lasts for an average of 11.9±0.1 days with a range of 11-13 days (Segura et al. in press). Hatching success is reported at 0.84±0.02, with the average hatchlings per nest being 2.5 ± 0.1, with a range of 1-4 (Segura et al. in press). Chicks remain in the nest for an average of 13.9 ± 0.1 days (range 12-18 days) (Segura et al. in press). Both parents feed nestlings before the fledgling stage (Pendleton 1996, cited in Lindholm 2003), and are fed with the mashed pulp of tala and white mulberry fruit (de la Pena and Pensiero 2003). Nestling survival rate is reported at 0.81 ± 0.03 (Segura et al. in press). After fledging, the male guards and feeds the juveniles, and they flock with their parents until they mature (Pendleton 1996, cited in Lindholm 2003). Juveniles will remain at the breeding sites at least through their first winter (Segura et al. 2014). Nest success rate was complementary with amount of tree cover, where one study listed 6 of 69 nests successfully producing at least one fledgling (Segura and Berkunsky 2012), and another listing a 26% survival rate from 367 nests (Segura and Reboreda 2012a). This rate would decrease as the season went on possibly due to predators finding more nests as time went on (Segura et al. 2012), but despite the low average breeding pairs would make multiple attempts over the season which could raise chance of success (Segura and Reboreda 2012a), with pairs having an average of 4.4 ± 0.2 nesting attempts per season (Segura et al. in press). Most nest failures, 62% in 397 nests, were a result of predation, while 11% of nests were abandoned (Segura et al. in press). After a predation event, the breeding pair builds a new nest in the same area (Segura 2011, cited in Segura et al. 2012), and the average time from nest failure to new nest is 8.2 ± 0.3 days, while the average time from fledglings successfully leaving to a new nest is 28.3 ± 2.1 days (Segura et al. in press). Red-crested Cardinals also are affected by brood parasitism by Shiny Cowbird (Molothrus bonariensis), with nest parasitism rates of 2 of 69 nests (Segura and Berkunsky 2012), or 9 of 130 nests (7%) where a single egg is deposited during the cardinal’s nest construction or egg laying periods (Segura and Reboreda 2012b). Female Shiny Cowbirds puncture existing eggs before laying the parasite egg (Segura et al. in press). In laboratory tests by Segura and Reboreda (2012b), Shiny Cowbird eggs had a rejection rate of 98.5% (67 of 68 lab nests); where in 64 of 66 nests the egg was ejected within 24 hours of introduction and the remaining two were ejected between 24 and 48 hours. Shiny Cowbird eggs are white in color, which possibly contributes to Red-crested Cardinal’s rejection in comparison to their own greenish eggs. Red-crested Cardinals do little to no damage to their own eggs during ejection, pecking and puncturing the cowbird egg and carrying it away from the nest in its bill by grasping the eggshell (Segura and Reboreda 2012b). No reports have been given as to Red-crested Cardinals caring for Shiny Cowbird hatchlings.