We had a pair of American Goldfinch (Carduelis tristis) at the bird feeder today. The male is the one on the left with the black cap and dark wings, while the female is the one on the right.
This species does not start its breeding period until late in the summer; it is one of the latest nesting birds. It usually does not start until late June or early July, when most other songbirds are finishing with breeding. The late timing may be related to the availability of suitable nesting materials and seeds for feeding young.
Goldfinches are mostly monogamous, but a number of females switch mates after producing a first brood. The first male takes care of the fledglings while the female goes off to start another brood with a different male.
They are an abundant, widespread species and their populations appear stable.
References:
Cornell Lab of Ornithology's All About Birds
