 The American goldfinch is a diurnal feeder. According to the Cornell Lab of Ornithology, the species is one of the strictest vegetarians in the bird world. It is mainly granivorous, but will occasionally eat insects, which are also fed to its young to provide protein. Its diet consists of the seeds from a wide variety of annual plants, often those of weeds grasses and trees, such as thistle, teasel, dandelion, ragweed, mullein, cosmos, goatsbeard, sunflower, and alder. However, it also consumes tree buds, maple sap, and berries. It will eat at bird feeders provided by humans, particularly in the winter months, preferring Niger seed (commonly and erroneously called thistle seed).
