From Wheatgrass Meadow — A Ghostly Hummer – by Barb and Rolf Sigford
Fall is a time of bright colors, especially the flaming gold of the aspens, the rich copper as the oaks change, and the bright and blazing yellow of the cottonwoods. Many of the resident bluebirds have moved on, but new groups of cheery blue migrants come through on their way south. The more subtle colors are still around: the mauve, metallic bronze of the Band-tailed Pigeons; the rufous wings, with pearl white beads, on the wings of the kestrels; the iridescent blue-black of the ravens and crows.
Normally the color we see is reflected light. When sunlight, for example, falls on a reddish squirrel, most of the colors in the beam of sunlight are absorbed by the pigment in the squirrel’s fur. But the red light is reflected, and we see the squirrel as red. Sometimes, sunlight is broken up into its component colors, and we see a rainbow. A prism will also do this, or, rarely, a window in the late afternoon will refract or bend the sunlight into its various individual colors.
Some birds have pigments that will refract light, so we see different colors in the same spot as the bird changes position. A hummingbird’s throat may look violet, or blue, or black, or even red as it turns its head. These colors are a vibrant, lustrous sheen. A Violet-Green Swallow may seem to change color as it moves, first more green and then more violet on the back. Of course, these birds may reflect light in the ordinary way from pigments in the feather, while another part of the body is doing more refracting because some of the feathers structurally bend the light (which seems so much more dramatic!).
Other birds take on color from what they eat. For instance, flamingos turn pink from their diet, which includes pre-made pigments like carotenes. House Finches normally have raspberry coloring on their heads, throats, chests, and rumps, but with different food sources this coloring may be replaced by orange or yellow.
The yellow aspen leaves we so admire change in the fall when the green pigment, chlorophyll, degrades. The green fades, but other pigments are already present in the leaf with the chlorophyll. When the chlorophyll fades, the yellows of the carotene pigments are revealed.
We sometimes take these fascinating colors for granted, but some animals and birds cannot produce any color because of a genetic defect, making them unable to properly produce melanin (the primary color pigment). These albinos are rare, both in humans and in other birds and animals. But we may occasionally see an albino person, or squirrel, or bird, and it can be a very startling encounter. In a true albino bird, in addition to white feathers, the bill, the legs, the feet, and the eyes will be affected. The eyes of an albino appear pink to red, from the underlying blood vessels.
Even more interestingly, some birds and animals can make some color pigment (melanin), yet not enough of it-or not in the right places on the body. These birds and animals are leucistic, sometimes called partial albinos. They may be a pale color overall or may have bright or dark colors in one spot and white in other areas, giving a piebald effect. The bill, the legs, the feet and the eyes will typically have a more normal color. A bird you know well may not be immediately recognizable and difficult to identify.
We know genetic mutations or expressions cause this leucism, but we don’t know how to pronounce it! Generally you hear a soft “c” sound as in “Lucy.” Others insist on a hard “c” sound so it comes out like “k.” I prefer the softer sound, which reminds me of Santa Lucia. The hard “k” sound certainly does occur in English “leuc” words but usually this is followed by a “o” as in the white blood cell, leucocyte, which is always pronounced “leukocyte.” So the choice is yours.
Birders in Tucson the last couple years (including visitors from Coaldale) have had numerous opportunities to see a leucistic Red-tailed Hawk. It looked much more like a White-tailed Hawk! Or basically a white-all-over hawk. And it was kind enough to hang around in one area frequently, so troops of people could see it.=
Then, over the summer, right here in Coaldale, we had a leucistic hummingbird at our feeder. This bird had more of the muted type of leucism; it was overall a pale, ghostly greyish, but the distribution of lighter and darker greys was similar to the pattern of colors in a normal hummer. We think this lady was a juvenile Broad-tailed hummer, based on characteristics other than color such as wing length, curve of the bill, and the company she was keeping. Normally Broad-tailed hummers are a greenish color on the back with orange on the flanks and rufous on the outer tail feathers near the body. The males of that species make a characteristic trilling sound as they fly; our lady was a quiet flyer. She was quite feisty, often chasing other birds. Hummers are notorious for such aggressive behavior but not so much the females. We wondered if she had been picked on because of her color. (Perhaps “bully” is the modern term; she may need counseling).
Watch the woods and trees and feeders. Leucistic and albino animals are around, especially birds and squirrels. They are equally as interesting as the pretty and flashy-colored critters. And remember that carotene pigments are widespread in nature, not only in the tree leaves and the crustaceans eaten by flamingos, but also in carrots. Eating massive amounts of carrots turns human skin yellowish and can mimic the jaundice of liver failure (except in carrot overuse the eyeballs stay white)!
You can see photos of the Sigfords’ leucistic hummingbird as well as links to other leucistic birds here.