The American goldfinch waits until late July to nest, when thistle seed peaks
Most North American birds are finished breeding by midsummer, but the American goldfinch barely starts before late July. Almost nothing else native to the continent nests so late. The reason is its diet: it lives on seeds, and thistles, sunflowers and other weeds are at their most generous in late summer.
This small finch, 11 to 14 centimetres long and weighing 11 to 20 grams, breeds from coast to coast across North America and winters from southern Canada to Mexico. Its conical beak is built for plucking seeds from seedheads, and nimble feet let it cling to swaying stems while it eats. People have mostly helped it: feeders boost survival in suburbs, and cleared forest opens up the weedy meadows it prefers. Attempts to introduce it to Bermuda and Tahiti, though, never took.
It is the only cardueline finch that moults twice a year. In autumn it replaces every feather; in spring, all but the wings and tail. Afterwards the male turns brilliant lemon yellow, coloured by carotenoid pigments from plants, with a jet-black cap, while the female stays mostly brown with a yellow bib. Both sexes' beaks shift from pink to bright orange. In winter the male fades to olive, looking much like the female.
You can spot one by its flight, a rollercoaster of quick wingbeats followed by a folded-wing glide, often with a per-twee-twee-twee call during the flapping and silence on the coast. Courting males sing and chase zigzagging females, then, once paired, mark a territory by warbling from perch to perch and performing a looping plunge display. The birds flock sociably outside the breeding season, and their aggression while nesting is short-lived.
Faced with snakes, weasels, blue jays, hawks or cats, goldfinches do not fight back; they only sound the alarm. The oldest known wild individual lived 10 years and 5 months. Carl Linnaeus first described the species in 1758, in the 10th edition of Systema Naturae.
Source: American goldfinch
