Birds as different as people
cutline: This leucistic female House Finch was observed last week in West Fargo. It's white head feathers would normally be a plain gray-brown.
People watching. We all do it I suppose. I even know some folks who will head to the mall with nothing else in mind but watching people. Whatever the motive, it can be interesting at times. In the course of this pursuit it becomes readily apparent to even the casual viewer that the human race is quite varied. We come in different sizes, different colors, different shapes and different races. Not to mention the highly diverse way we all dress.
When I became interested in bird observation some years ago, I began to collect field guides. While these books can be very helpful, they also became a minor source of frustration. Often enough the pictures (or illustrations) in the guides would not quite match what I was seeing. As good as the books' illustrations were, they were almost, well, too good. Herein lies the point. The variety we witness in humans is often matched in nature as well. And most field guides show the perfect bird in the perfect pose--something rarely encountered in the field.
One friend of mine has an uncanny ability to pick up on any little imperfection on a bird. "It's got a wing feather that is a little shorter than the rest," he'll say. Or, "the beak on that bird looks different." I blame it on the fact that he has much more expensive binoculars. But it indicates two things. One, he is extremely observant with even the most minute details. And, two, there are more differences among birds than most would think.
We aren't talking about the different plumages between the sexes or between seasons here. We're speaking to the varying morphology of individuals within populations.
In ornithology (bird science), this variety has often led to uncertainties in bird classification. It wasn't all that long ago Snow Geese were thought to be two different species--the Blue Goose and the Snow Goose. The difference between these two birds is obvious, leading early experts to conclude they were separate. One, the Snow Goose, is completely white with black wingtips. The other- Blue Goose- displays dark gray-brown coloration over most of its body. It turns out they aren't that different after all, the bird just comes in two color morphs.
Examples of fickle feathering are numerous. Our resident Eastern Screech Owl is a mostly gray little bird in these parts. Yet go toward the eastern or southern states and you will run across red and brown birds of the same species. The ubiquitous Red-tailed Hawk is perhaps the king of variability. There are dark ones and light ones and barred ones and solid ones- depending on where you are on the continent.
Other phenomena occasionally rise up to confuse bird observers also. Yes in the world of birds, as with the human race, there are genetic (or environmental) abnormalities that sporadically show up. Weird stuff like albinism, melanism, xanthochroism, and leucism. All these terms refer to peculiarities that occur in bird coloring.
Without getting too technical, albinism is a genetic change inhibiting an enzyme dealing with pigment formation. Total albinism in birds (with all white feathers and pink eyes) is rare, but lesser degrees of it are fairly frequent. It's been noted in hundreds of bird species. Leucism (loo-kism) is slightly different than albinism (although some authors use them interchangeably) in that pigment cells are not present at all. But, like albinism, this runs the spectrum from complete coverage to perhaps one white feather.
As readers may surmise, the realm of creatures isn't perfect. Just as we humans display our flaws, so it is in nature. Watch more closely and you may just be lucky enough to pick out one of the unusual variations. In the end, isn't there some degree of satisfaction knowing everything is just a little different?