Fabulous finches: Birds wear colors they eat
If you have a bird feeder in the continental United States, you have almost certainly been visited by house finches. On both sides of the Mississippi their hungry flocks coat feeders like displays of cherry and root beer lollipops. They park themselves at providential feeding ports or flutter at their neighbors to win better ones. Off the feeders, they are singers who greet mornings with ubiquitous cheery notes, mixing reedy discord with melodious clarity, any time of year. They seem perfectly comfortable making our houses their homes.
House finches fledge from the nest dressed in brown, heavily streaked on their undersides. But as they molt, the males develop a bright red wash over their head, breast and rump. Young females, too, may briefly wear red on their rumps. As adults, females prefer brightly colored males.
Bright colors, however, are not genetically inherited. Like most birds, finches can’t actually make red or yellow pigment. Rather, these molting males incorporate pigments from the foods they eat. In addition to black oil sunflower seeds at feeders, they savor a variety of fruits and vegetables that contain the carotenoids — yellows, reds, and purples — they absorb into feather-paint.
Because their food varies geographically, male finches in some areas will wear a more orange or even yellow hue instead of red feathers. Further, because the birds don’t migrate, you may be establishing a particular finch color in your neighborhood with your local blend of fruit trees, berries and vegetable gardens.
The males, no matter their brightness, are famous for singing exuberantly near their mates while the female does the work of nest-building, laying eggs and incubating them. A male may bring food to his mate during this period, and he fully assists in tending their nestlings. The system works for them: house finches lay two to six eggs in each clutch, and will clutch as many as six times a year. With human help they have spread far and wide.
Native to the western US and Mexico, these desert-lovers were introduced to New York in 1940. From there they expanded quickly throughout the east, substantially replacing the purple finch of the declining eastern forests. Before conquering the East they were introduced in Oahu, and became abundant throughout Hawaii over a century ago.
Hawaiian birds are famously fitted to particular plants or lifestyles, and have not done well as their world has changed. House finches, on the other hand, are generalists; typical of birds that thrive in new situations. They nest freely in not just their traditional Western scrub and cacti, but now in shrubs, trees, hanging plant-pots, on building ledges or over porch lights. They readily flock to feeders when their fields of seeds are transformed. Strung wires serve for their singing posts. House finches roll with the punches, and that has allowed them to prosper.
Go to http://www.wintuaudubon.org/ for local birding programs and a schedule of activities open to the public.