The American male Goldfinch is not always this color. In the spring during breeding season he changes into this bright yellow color. However, by fall, he becomes a dull olive brown, making him hard to distinguish from the female. Both the male and female are mostly vegetarians, and feed their young regurgitated seeds. The male has also become a symbol for summer, because their bright yellow plumage matches blooming sunflowers and black-eyed Susan’s.