Of a Feather: Late breeders

By BILL CHAISSON
All through the winter I and most people have a troupe of goldfinches visiting the feeder(s). They famously prefer niger (or nyjer or thistle) seed over all others, but they happily plow through sunflower seeds as well. During the winter goldfinches are not gold, although you can still see glints of bright yellow here and there on the males. They are often in loose groups of half a dozen or so when they approach a feeder, but in the winter I have often seen larger groups making their way across the treetops, sometimes in the company of other small finches like pine siskins.

In April the males start sporting patches of yellow as they molt into their breeding plumage. I have not watched them closely enough and singled out individuals well enough to determine whether these patches appear in a consistent pattern from bird to bird. The molt does take place over a period of weeks and by May they have their flashy yellow and black ensemble fully in place.

Toward the end of their molt the males begin to sing on warm days in the early spring. They don’t give the full throated, cascading canary-like song of the breeding season, but rather sing with a sort of puzzled tone that suggests they are feeling the hormones, but not the full spirit as yet.

Goldfinches fly with a characteristic undulating pattern, flapping and gliding so that they seem to be on a rollercoaster in the air. There is something comical about the fact that their two-noted flight call is delivered in perfect synchronization with the pattern. As they reach the bottom of each trough, they bleat out the dit-dit sound, rise up to a crest and then seem to have the dit-dit forced out of them again as they bottom out.

As spring advances and other birds begin to pair off and set up territories, goldfinches continue to wander about in loose groups. Most of us think of all birds as breeding at pretty much the same time: April, May and June, every year. In fact, bird species tend to breed at the same time that they assured of a good food supply for their young. Accordingly, insect eating birds can set up housekeeping as soon as their preferred suite of invertebrates hatches and is available for consumption. Warbler migration seems timed to sweep north with the leaf-out of the trees but is more directly tied to the first appearance of the insect larvae that feed on the succulent new greenery. Owls, on the other hand, start raising young in the middle of winter, apparently so that when the owlets fledge and start hunting on their own, they will have a good long time to learn how to do it.

The goldfinch fondness for thistle seed at your winter feeder is what causes them to put off setting up territories, building nests and raising young until July and August. They have to wait until the thistles bloom and go to seed and like most meadow flowers, thistles bloom from mid summer into the fall. They will actually eat the seeds of many species in the aster family, but the majority of them flower and produce seed after mid summer. They also line their nests with the fluffy “pappus” material that forms part of aster flower heads.

How then do the adults survive until the asters bloom? Goldfinches are also quite fond of the seeds of many trees, including birch, alder, and elm, and all of these flower in the spring and have gone to seed by May.

Goldfinches incubate their eggs for about two weeks and then spend about another two weeks raising their nestlings. Once they are fledged, the young follow the parents out into the fall meadows full of flowers and seed heads and learn to forage on their own … until they all show up at your feeder together.