Breeding

There is very little information on the reproductive biology of Blue Seedeater. The only known nest is one discovered in July in Mexico by Rowley (1962). Fledglings also have been seen in Costa Rica in early September (Stiles and Skutch 1989). The nest reported by Rowley (1962) was a small cup in the forks of a slender branch of a Lantana, 2.4 m above the ground. The nest was constructed entirely of plant material, with an exterior of the nest made of coarse grasses, which were woven around the forks of the branch, and a cup that was lined with fine grasses fibers. The external diameter of the nest was 80 mm, and a depth of 55; the cup was 50 mm in diameter, and a depth of 40 mm. This nest held one egg of a Bronzed Cowbird (Molothrus aeneus), and two eggs of the seedeater. The eggs were pale blue and unmarked, and measured 18.5-19 x 14 mm.