The fascinating finches

StoryImage( ‘/Images/Story//Auto-img-11865237248552.jpg’, ‘Photo by Norma Hedeen’, ‘A goldfinch shares a feeder with a purple finch at a feeder in the yard of Norma and Mike Hedeen in Rockford.‘);

Beyond a doubt, the three most beautiful birds I have seen in the wild in North America are the painted bunting, the indigo bunting and the goldfinch. The painted bunting does not occur this far north in the United States, but the other two are regular visitors to my feeders. The goldfinch is by far one of the most common visitors I identify that comes to my back yard during the summer season.

The goldfinch is sometimes called the wild canary as it is about the same size as a canary, and the male during the summer breeding season has a striking yellow body with white-barred black wings, and he wears a black cap jauntily shoved forward on his head. The rest of the year, he is rather olive drab in coloration, as is the female the entire year.

This striking difference in appearance of the male and the female during the breeding season is known as sexual dimorphism and is an adaptation to make sure the female of the species does not make a mistake when selecting a mating partner. If the female would make a mistake and mate with a similar but genetically different species, the act of procreation would be wasted. Nature is quite frugal in that respect.

Goldfinches are mainly seed feeders and often do us a favor by coming onto our lawns to feed on dandelion seeds, which they relish, as well as thistle seeds.

Except during the breeding season when male and female pair off, they go about in small groups, making delightful music as they flit about the landscape. They fly about with a long, bounding motion as if they were riding waves in the air, and at each dip in flight, they utter a sound that seems to say “Per-chick-o-ree.” Their sweet voice has been compared favorably with that of a canary. It is easy to know when goldfinches are in the area without seeing them because they are rarely silent when feeding, resting or flying.

Except in the extreme northern United States, the goldfinch is a year-round resident. I think I have seen them in my back yard during the winter, but when the males loses his characteristic yellow body and black wings with white bars and assumes the olive yellow color, it is difficult to distinguish him from similar birds. Pine siskins, redpolls, and some others that come down from more northern regions to spend part of the winter with us superficially resemble both the male and female goldfinch, and a mistake in identification can be easily made.

It is interesting to note that when I lived in France near the city of LaRochelle, the European goldfinch was common, and, though it is a distinct species, its habits are quite similar to its American cousin.

There are many different species of finches, but none perhaps more famous than about 14 different types that inhabit the Galapagos Islands some 500 miles off the coast of Ecuador. These finches greatly assisted Charles Darwin in formulating his theory of the evolution of species by natural selection when he visited the islands in 1835.

In the distant past, a founder colony of a species of finch was accidentally blown by a high wind from the mainland and made landfall on one of the islands of the archipelago. After they established themselves, a few were blown to neighboring islands and had little chance to return to their ancestral island. Being genetically isolated, they evolved into 14 different species. On the new islands, the finches found there were ecological niches that were unoccupied, and they moved into them. These birds adapted to the new environment and became insect feeders, cactus feeders, worm and seed feeders. The shapes of the bills changed to accommodate the new feeding habits. One even acquired the practice of breaking off a cactus spine and using it as a spear to extract insects from plant tissue.

Darwin saw that the birds were similar to each other, with the major difference being the different shapes of the bills, which coincided with their feeding habits. Clearly, they had all evolved from a single species. Today, these birds are known as “Darwin’s Finches” and continue to be studied in detail by biologists from all over the world.

Though Darwin’s theory was certainly not predicated alone on his observations of the finches on the different islands, the finches of the Galapagos supplied an important clue in his solving of the great mystery of how new species arise.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

from the August 8-14, 2007, issue

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