Goldfinches and the season of milkweed and asters

September 16 | 2022

For most of us, seeds are a starting point, the venture capital we invest in our farms and gardens, while for the American goldfinch, last of the summer breeders, seeds are an end in themselves. The uncompromising vegetarians of the avian world, goldfinches postpone nesting until mid-summer, when thistle, milkweed, sunflower, and aster promise a banquet for their young.

It’s the female goldfinch that builds the nest, as elaborated by the 19th-century writer and naturalist Catharine Parr Traill in her book Pearls and Pebbles: The female bird “selects or rejects this or that . . . wool that the thorns and bushes have caught from the sheep and lambs; hair that cow or horse has let fall; grey lichens picked from a wall, and tender green moss from a fallen tree. Taking here a bit and there a morsel, to give strength or elasticity, needful warmth or softness, she weaves all together according to the family pattern.”

If goldfinches count among the last to nest and breed, those that migrate are also among the last to leave. Scientists have observed the birds mulling a crossing over a body of water, then abruptly losing their nerve and returning to the shoreline. When they do eventually summon up the will to go, the males, as depicted on this letter box in their breeding colours, will have begun to fade. The last chance to admire their luminous yellow, a distillation of the summer sun, is in September.