The American Goldfinch nest is built in late summer by the female in the branches of a deciduous shrub or tree at a height of up to 10 m (33 ft). The nest-building lasts approximately six days, during which time the female works in 10–40 minute increments. The male frequently flies with the female as she collects nesting materials, and though he may carry some materials back to the nest, he leaves its construction to the female. The outer shell of the nest is built of bark, weeds, vines, and grass. The inside diameter of the finished nest is about 6.5 cm (2.6 in). The rim is reinforced with bark bound by spiderwebs and caterpillar silk, and the cup is lined with plant down from milkweed, thistle, or cattail. The nest is so tightly woven that it can hold water, and it is possible for nestlings to drown following a rainstorm if the parents do not cover the nest.