American Goldfinches breed later than most North American birds. They wait to nest until June or July when milkweed, thistle, and other plants have produced their fibrous seeds, which goldfinches incorporate into their nests and also feed their young.
Goldfinches are among the strictest vegetarians in the bird world, selecting an entirely vegetable diet and only inadvertently swallowing an occasional insect.
The nest is constructed by the female in 3 stages. Stage 1 involves building an open cup of twigs connected by spider silk. In stage 2, a tighter cup of small roots and plant debris is formed. During stage 3, a soft lining of plant pappus or other “downy” material is added to line the nest.