Eared Quetzal breeds in the mid to latter part of the year, beginning between June and August, and ending in October (Howell and Webb 1995, Johnsgard 2000, Gonzalez-Rojas et al. 2008), although Lammertink et al. (1996) report whistling series by males and females from March to October. Taylor (1994) speculated that the birds timed their breeding season to coincide with the abundance of fruits and insects after the rainy season in July and August.
The quetzal is a secondary cavity nester, meaning it adopts a tree cavity that has already been made (Miller and Chambers 2007). Gonzalez-Rojas et al. (2008) measured 14 nests in Chihuahua, 9 (64.3%) in woodpecker cavities (with the rest in natural cavities); 6 were in live trees with no sign of decay, and the other 8 were in dead trees. Eleven of these nests were in quaking aspen (Populus tremuloides), two in Durango pines (Pinus durangensis), and one in a Mexican white pine (P. ayacahuite). The mean height of the nest trees was 16.9 ± 7.8 m while their mean dbh was 0.52 ± 0.2 m. The mean height of the nest cavities was 11.4 ± 4.1 m up the tree (n = 14) and their entrances averaged to 9.0 ± 1.6 cm high by 9.0 ± 1.8 cm wide (n = 10). The mean depth of three nests was 25 ± 18 cm, their internal diameter was 20 ± 8 cm, and their external diameter was 34 ± 23 cm. These nests (n = 14) were found between 2330-2600 m above sea level. Three were reused during multiple years (during 6, 4, and 2 years respectively; Gonzalez-Rojas et al. 2008). A nest independently found in Chihuahua was found around 22 m up a Mexican White Pine in what had probably been a Northern Flicker (Colaptes auratus) hole, halfway up a canyon. In 1993, this hole had been used during four consecutive years (Taylor 1994). The only nest found in the USA, in Arizona, was around 9 m up a dead bigtooth maple (Acer grandidentatum), which was on a canyon wall around 23 m above its floor, around 2042 m above sea level (Taylor 1994). The quetzal’s ability to nest in canyons and near river systems, and possible preference for these habitats, may explain why it may be found in mostly logged areas nearby, as these places are often left undisturbed in its range (Lammertink et al. 1996).
The eggs are light blue to greenish-blue and oval (32.5 x 26.3 mm, n = 1; Gonzalez-Rojas et al. 2008). The mean clutch size for 28 nests in Chihuahua was 2.8 ± 0.9 eggs (n = 28, range 2-4 eggs; 13 nests had 2 eggs, 7 had 3 eggs , and 8 had 4 eggs). The incubation period lasts around 22 days (n = 1; Gonzalez-Rojas et al. 2008). In a nest monitored in Mexico for three days during this period, the female spent 54% of daylight observation time on the nest, the male 33%, and it was unoccupied during 13% of the time (Lammertink et al. 1996). The female occupied it during the night but was relieved by the male between 5 minutes before and 25 minutes after sunrise. The male gave a wheeeuh chk call upon arriving and flight calls, while the female would whistle softly from the nest or nearby (Lammertink et al. 1996). In a study in Chihuahua, the females at six nests incubated from early afternoon (13:10 -13:45) until the early morning (06:30-07:00) while the males incubated during the remaining ± 7 hours (Gonzalez-Rojas et al. 2008). Both sexes feed the nestlings when they hatch (Gonzalez-Rojas et al. 2008, Taylor 1994). Food items include larvae, butterflies, and lizards (Sceloporus sp.; Gonzalez-Rojas et al. 2008). No information was found on brooding behavior.
The nestling period ranges from 29 to 31 days (n = 5; Gonzalez-Rojas et al. 2008). When they hatch, nestlings are blind, naked, and pink-skinned. Their feathers begin erupting from shafts by day 5 after hatching and nearly cover the birds between days 10 and 16 (Gonzalez-Rojas et al. 2008). The nestlings collected in Arizona were reportedly covered in black and yellow down (Taylor 1994), but they were most likely in this period and the 'down' was probably erupting, fluffy, contour feathers (similar to the Resplendent Quetzal; Johnsgard 2000). These feathers emerge earlier than in most lowland trogons, supporting the notion that highland species may grow feathers earlier for protection against the cold (Gonzalez-Rojas et al. 2008). The body mass of two nestlings was 18.3 g on day 3 after hatching, 26.1 g on day 5, 47.5 g on day 10, 81.5 g on day 16, 92.9 g on day 19, and 96 g on day 28. Their wing chord was 12.8 mm on day 3, 15.2 mm on day 5, 29.4 mm on day 10, 62.2 mm on day 16, 86.7 mm on day 19, and 111.7 mm on day 25 (Gonzalez-Rojas et al. 2008). Fledglings have spotted wing covert tips, arranged in loose rows. Their breast and belly are mottled, they have a blue tail and generally resemble the adult female (Taylor 1994). No more information on the fledgling period found.
No reports of multiple clutches or brood parasitism found.
One study found that success rates appear to be high for Eared Quetzal nests (Gonzalez-Rojas et al. 2008). Of 80 eggs, 70 hatched (87.5%), 1 did not hatch, 2 were depredated by a squirrel, and 7 (in two nests) were lost when the nest tree fell. Of 70 nestlings, 67 fledged (95.7%), resulting in 25 of 29 nests (86.2%) producing at least one fledgling. During 6 years of study, the success rate in years with more than three nests was 100% (2001, n = 6), 66.6% (2002, n = 6), and 83.3% (2003, n = 12; Gonzalez-Rojas et al. 2008). The only nest found so far in Arizona failed due to a cold snap, which killed its nestling (Taylor 1994). Compared to Resplendent Quetzal (Pharomachrus moccino) and other trogons, Eared Quetzal has a higher nest success rate. This may be due to a lack of arboreal snakes in its habitat and the presence of fewer potential mammalian predators when compared to more tropical regions (Gonzalez-Rojas et al. 2008). Eared Quetzal nest accumulates feces and other waste from its growing nestlings, which creates an unpleasant smell that may deter predators. The hissing ‘stressed’ calls, similar to those of nestling snakes, which the nestlings make when disturbed may also serve an anti-predatory function (Gonzalez-Rojas et al. 2008), although this hypothesis has not been tested and could potentially not function in a place with no arboreal snakes.