by John Shackford
The Blue-gray Gnatcatcher (Polioptila caerulea) is a breeding bird in most of Oklahoma, although it is decidedly rare in the Panhandle, especially in the 2 easternmost counties, Beaver and Texas counties. At 4½ inches it is one of our smallest birds, excluding hummingbirds, even though much of this length is the result of a long tail, which it flips about as it moves through the trees. It weighs only 0.2 oz. (6 grams); thus, you could mail 5 of them on one first-class stamp (if they were flat enough!). This is the only gnatcatcher that has been found in Oklahoma.
The best description of the bird I have heard was by one of our members, Laurie MacIvor-Gillum, who saw one, amazingly, on our Christmas Bird Count a number of years ago: “It looked like a miniature mockingbird” was her description to me. The bird is bluish-gray over most of the upper surface of the body with a white breast below. The upper surface of the tail is black, except for the outer 2 tail feather, which are mostly white. Looking from below, the undertail looks almost all white. This is an important identification point that separates the Blue-gray from the Black-tailed Gnatcatcher, which is found in southwest Texas, southern New Mexico and on further west in the southwestern U.S. There is one other gnatcatcher in North America, the California Gnatcatcher, found in southern California and south into Baja California, the northern race of which is an endangered subspecies.
Not too many years ago while birding in my yard, I found a pair of Blue-grays building a nest; I believe it was in an oak tree. The thing that surprised me was that the birds paid no attention to me (so far as I could tell by observing them) even though I was only about 20-25 feet away. They went blithely about their business of building a nest—I just was not a part of their world to be worried about. It was a pleasure to think about this in terms of the gnatcatchers’ world. They had everything they needed to carry on life and reproduction within a quite limited area it seemed to me; their needs could be met on a gnatcatcher’s scale: It would not take much space for them to easily feed on small flying insects, insects that at least one ornithologist had rightly noted as being too small for him to see. It would not have required much area to gather the lichens and other nesting material for its very small nest. And I suspect they are too small a bird for them commonly to be a prey item.
I have thought about these “miniature mockers” and their miniature “world.” Blue-grays can winter as far south as Guatemala. The birds in my yard had migrated northward a long way to take up a little territory in a patch of woods north of Edmond, Oklahoma, perhaps not far from their breeding territory of the previous year. So we have a long migratory traveler with probably a very precise guidance system to return, I’m guessing, to a very precise nesting area. This seems to me to be a prescription for the development of divergent populations, as there would seem to be a high probability that populations would tend to isolate themselves from other populations over time.
Another thing which factored in to my thinking on this subject of isolated populations was the Blue-grays that occur in the Black Mesa area at the extreme western end of the Oklahoma Panhandle, in Cimarron County. It seems to me that the Mesa birds are not exactly like the Blue-grays in central Oklahoma—the Mesa birds seemed to have slightly more prominent black above the eye, for instance, but, again, maybe this is just my imagination. Dr. George M. Sutton (1967, Oklahoma Birds) said that, although he was confident that the Cimarron County gnatcatchers were Blue-grays, he was not sure what subspecies nested in the Black Mesa area, although at least 1 specimen from the area appeared not to be of the eastern subspecies. He stated that more work needs to be done.
A final thought on all this is that I would not be surprised if some day North American gnatcatchers were divided into more than 3 species; there are considered to be about 9 subspecies among the 3 species at present. It is good to remember that species vs. subspecies are human constructs that nature does not adhere to—she has a sliding scale. Reclassifications are often the result of new genetics studies or of intense study of breeding success between 2 populations of birds. Sometimes we have to pity the experts who are tasked with making decisions on certain difficult species/subspecies questions, because there really may not be a clear answer.