Goldfinches and thistles are creatures of high summer that share a life-sustaining bond. The common bull or spear thistle (Cirsium vulgare) grows and thrives under a wide range of conditions, including many that other plants find inhospitable. Goldfinches (Spinus tristis) frequent the fields, roadsides and other places where thistles are common.
I think of the sparrow-size goldfinch, in its yellow courting dress, as a temperate zone parakeet (though the species are unrelated). My father always used to call goldfinches “salad birds,” though I have never seen the term anywhere else. In August the salad birds swoop, glide and flit through the trees and fields, in search of nourishing thistle seeds. They also capture the thistle down that adheres to those seeds, enabling them to float on the breeze and sow themselves over a wide area. The birds use the thistle down to line their nests, making them snug and cozy for the young finches. I suspect that while gathering down, the finches also help spread some of the seeds, thereby perpetuating the thistles.
Thistles are often treated as unwelcome weeds, but perhaps it is useful, from time to time, to see them through the appreciative eyes of the salad birds.