The Last Yellow Rose of Summer
Aug 24, 2018
Across their wide North American range, American goldfinches are just about the last birds of summer to build nests, lay eggs and raise young. By waiting to begin the reproductive cycle, they are assured a plentiful supply of seeds on mature plants, such as the thistle. Goldfinches wait for the thistle to produce down for nest building as well as seeds to feed to their nestlings.
An added benefit to the late breeding is that goldfinches are able to avoid female brown-headed cowbirds looking for nests in which to deposit eggs. Substitute parenting by the cowbird is called "brood parasitism," and it is not beneficial to the offspring of other surrogate parents.
The female goldfinch selects the nest site and weaves a cup-shaped nest from grass and plant fibers, lining it with silky thistledown seen on page 3. The nest is so tightly constructed that some have been found filled with water after a heavy rain.
The male's role during the incubation period is to keep his mate well fed. Once the eggs hatch, however, both parents feed their offspring. Goldfinches are complete herbivores, so focused on seed for food that they even feed their nestlings regurgitated seeds.
The best reasons to keep feeding stations well stocked throughout the summer is the sight of a Nyjer-filled tube feeder with a male American goldfinch on every perch. Their dazzling breeding season plumage makes them look like lemon-yellow canaries. But when the male goes through its fall molt, the black cap disappears and the bright yellow dims to a drab, olive-yellow color. They are so different looking that many people ask, "Where did my goldfinches go?" Females remain a soft, olive-yellow color all year.
In much the same way as your backyard birds display different eating preferences, you will notice their different flying styles as well. The little yellow and black "roller coaster" approaching your feeding station is the American goldfinch, using its characteristic finch-style alternate gliding and flapping technique.