By Mic McCarty, Field Trip Coordinator, Board Member
While birding, we occasionally encounter strangely colored birds. Some have discolored areas, some have colors that are off (either lighter or darker) or we see truly rare albino birds. During the Pasco CBC Dec. 14, we found a khaki-colored Fish Crow.
“In rare cases, a bird does not produce melanin at a normal level or in a normal pattern. The resulting color patterns are referred to as being albino (white), leucistic (patches of pure white), or with dilute plumage,” according to Irby J Lovette and John W. Fitzpatrick, editors, The Handbook of Bird Biology.
True albinism occurs when a bird is completely missing melanin. I have not personally seen a true albino, but this Mourning Dove is close. The faint freckle like patch on the cheek, the dark base of the bill and the black eye keep this bird from being a true albino.
Low levels of melanin create a bird with dilute plumage. This is the case of this Fish Crow found in Paso County. This crow has a khaki-colored wash with a darker breast patch and light-colored eyes.
When an animal produces too much melanin, they are referred to as melanistic. The unusual color patterns can be the result of injury, poor nutrition, or a genetic mutation. Perhaps the most famous melanistic animal are the black panthers. Black panthers are color variants of leopards and jaguars.
Birds can have melanism, too.
“Melanism occurs when a mutation causes excess dark pigment to be produced in the feathers,” according to according to Irby J Lovette and John W. Fitzpatrick, editors, The Handbook of Bird Biology.
This American Kestrel is one such case. I initially thought that it was a Merlin because of the excessively dark plumage. The bolder, bigger malar stripes along with date and location makes this falcon a kestrel.
Other factors can also affect a bird’s appearance. Feathers can become paler if bleached in the sun of the southwest or become darker in areas with high air pollution. The berries they eat sometimes stain robins and waxwings.
Other interesting variations can change a bird’s colors. Sun bleaching, diet, and air pollution can affect a bird’s color. A field trip to Cedar Key once provided a pink dyed Laughing Gull! This particular bird may have encountered a chemical spill or might have been part of a research project.
For more information, go here.