Breeding

In Costa Rica and Panama, breeding is associated with wet seasons (Skutch 1954, Wetmore et al. 1984). In Costa Rica, breeding primarily occurs May-August, but may take place at a very low level until as late as January (Stiles and Skutch 1989).

Most information on the breeding of the Yellow-faced Grassquit is from Skutch (1954).

Nest: The domed nest is ovoid or, less commonly, globular in shape, with thick walls and a side entrance. The nest is composed of straw, grass blades, and weed stems, lined with fine pieces of grass inflorescences or shredded fibers. Average nest measurements are 14 cm high by 7.5 cm in diameter, with a side entrance of 3.8 cm diameter. The nest is constructed by both sexes, although the two birds rarely work together; the male initiates construction of the nest but sometimes contributes little afterward. Nest construction takes 3-6 days. The nest is placed in a grass tussock or in a low bush, from 0.2-1.8 m above the ground.

Eggs: The eggs are white, speckled with brown marks; the eggs are speckled throughout, but the marks are more concentrated on the larger end.  The most frequent clutch size is two eggs (n=38), but the clutch may be three (n=19) or even four (n=1). Only the female incubates. The incubation period is 12-14 days until hatching. Parental care: Both sexes provision the nestlings; the food given to nestlings apparently is regurgitated seeds.