Have you ever seen an unusually dark bird? Not a crow or a grackle or another species that we’re used to seeing dressed all in jet. No, I mean a bird that you recognized in shape — a dove, or a hawk, or a sparrow — but it was much darker in color than you expected.
Perhaps you were puzzled as to what species the bird was. It was probably what you thought from the shape, just a melanistic version. Melanistic birds have a dark appearance. They have abnormally large amounts of melanin in their feathers which creates the dark color. The plumage can be completely dark brown or black, or just have odd dark markings.
Melanism is sort of the opposite of albinism or leucism. In albinism and leucism, the all-white coloration stands out and there is no question. But a melanistic bird or animal often gets little or no attention from passersby. Observers often think they look dark because they are in the shadows, or maybe just wet.
However, hardcore birders will notice the differences, as they are looking for the common markings on any bird they spot. Birders check wing bars, eye stripes, the bill color and so on. Any slight variation will send some birders into a tailspin. They will take huge amounts of time discussing each of the variations.
Leucistic birds stand out dramatically, marking them as targets for predators. But birds that are darker in appearance have a better chance of survival. In many cases, they are less noticeable and blend better to the habitat. In addition, they are able to stay warm for longer periods of time.
If these are big advantages, why hasn’t natural selection made all birds black? Well, in many instances, camouflage is better than solid dark color. An owl or nighthawk that blends in with bark and dead leaves is better adapted than a black one. Also, melanistic birds frequently have trouble finding a mate, as they may be unrecognizable to others of their species.
But in some places, natural selection is hard at work spreading melanistic traits. In industrial areas such as western Pennsylvania, many animal species including birds, mammals and even insects have mutated into darker versions. This is referred to as industrial melanism. A darker camo blends in better with coal soot.
I don’t have a lot of field experience with melanistic birds. Years ago, I sighted an unusually dark red-tailed hawk. At the time, I took note but didn’t think much about what I was observing. It was not until years later that I learned about melanism and realized that bird was most likely melanistic.
Another sighting of possible melanism, was an eastern bluebird that nested in one of my bluebird houses for five years. This was on my spacious property back in Maryland. The five years of residency of the bluebird is about the life span of an eastern bluebird.
At the time, I did not think much about the strange black markings on his side. I just was thrilled he chose my property to live and mate. The bluebird was totally recognizable because of the odd markings, and now I believe he was partly melanistic.
All birds have variations in coloring. Most are so slight we barely notice them. This particular bluebird had two separate mates over the time I observed him. Many of the young were banded by my good friend Mike Callahan. He still is working as a naturalist back in Maryland. I never noticed to see if any of the offspring had similar dark markings. Most of the time, the bluebirds were gone by the time they matured.
If you see an exceptionally dark bird, make careful note of the body and bill shape. The eye color and leg color of many melanistic birds stays the same as normal for the species. The feather color is often the only change. Pay attention to nature! There are interesting things all around you.
Abbie Banks is a member of the Venice Area Birding Association, a group of folks who want to enjoy the environment and nature without the cumbersome politics of an organized group. For more info on VABA or to be notified of upcoming birding trips, visit AbbiesWorld.org/references.html or email her at Amberina@aol.com.