Of a Feather: What bird is that?

PHOTO BY STEPHEN MIRICK
On Sunday, Nov. 14, a birder reported seeing a western kingbird in Dover.

He took some photographs of it and shared them with the birding community because he wasn’t sure it really was a western kingbird. It was a little odd looking. Here is Stephen Mirick’s description of it from NH Bird Forum: “1) Relatively deep fork in the tail. Deeper than a “notch;” 2) White outer tail feathers (which led to the preliminary erroneous ID as a Western Kingbird); 3) Very pale gray head; 4) Gray feathering blending into mantle.; 5) Very long bill; and 6) Bright lemon yellow below with a distinct white upper breast and throat.”

Mirick, Jason Lambert, and Ben Griffith put their heads together and decided it was a hybrid bird and that one parent was a scissor-tailed flycatcher, but the other couldn’t be a western kingbird because the beak was too big and the yellow underparts didn’t jibe either. This steered them toward the other parent being either a Couch’s or a tropical kingbird, which are nearly identical and distinguished primarily by their calls.

This hybrid bird, descended from two birds with ranges (assuming it is half Couch’s kingbird) that overlap in south Texas, is very far from home. Scissor-tailed flycatchers (Tyrannus forficatus) migrate to southern Mexico and Central America for the winter. Couch’s kingbird (T. couchii) doesn’t migrate at all. (The range of tropical kingbirds, T. melancholicus, barely overlaps that of scissor-tailed flycatchers in northeastern Mexico, and they don’t migrate either.)

This avian melodrama made me consider the definition of species because I have been reading about how and when western science arrived at the concept in the first place. Years and years ago, when I used to subscribe to book clubs through the mail, I selected Daniel J. Boorstin’s “The Discoverers” (1983) as one of my premium choices (four books for $4.95, or whatever it was). This massive book has been sitting on my shelf now for almost 40 years. Earlier this fall I made it the book I keep by my bedside and read before I fall asleep. Part XII is called “Cataloging the Whole Creation.”

Chapter 54, “Learning to Look,” presents us with the story of Dioscorides, a Greek physician who lived in the first century A.D. As Boorstin puts it “His ‘De Materia medica’ (c. 77) surveyed botany mainly as a kind of pharmacology.” In other words, it was important to identify a plant quite accurately because of its curative qualities.

However, during the Middle Ages, while Dioscorides writings were preserved, they were gradually bastardized through poor copying and translation. Furthermore, the illustrations that accompanied them were copied from previous illustrations rather than using the plants themselves as models, and so drifted away from accurate depictions into decorative pictures that illuminated pages.

The equivalent for animals, the “bestiaries,” didn’t even begin as accurate surveys; they included a fair number of entirely mythical creatures. These various catalogs of plants and animals passed along through the medieval period include “kinds” of life rather than species. A particular kind could be described and even illustrated in many different ways. Life forms were all regarded as acts of Creation and their exact appearance was not particularly of interest. God could make a rose or a rhinoceros any way He wanted.

It was John Ray (1627?-1705) who once again began to look as closely at Nature as Dioscorides had. Ray did not believe in evolution; he believed he was classifying the Creation, but he embraced the maxim “Nature does not proceed by leaps” and, as Boorstin puts it “sought out ‘middle terms,’ forms that stood between others to fill out the spectrum of the creation.” And although Ray assumed that each form had been created by a miracle, he called each one a species, defined as “a set of individuals who give rise through reproduction to new individuals similar to themselves.”

Carolus Linnaeus (1707-1778) continued the work of Ray, but is justifiably famous for his creation of the binomial system of classification. The scissor-tailed flycatcher was originally named Muscivora fortificata by Johann Gmelin in 1789. Gmelin, a German disciple of Linnaeus, worked with the Swedish scientist while he was based in the Netherlands.

Early Modern workers had used medieval Latin to identify species, but the names were often very long and constituted a complete description of the appearance, behavior, habitat, and geographic range of the plant or animal. These were difficult to remember and took a certain amount of time to write down. According to Boorstin, Linnaeus invented the binomial classification as shorthand for his students to use in the field.

But the names remain descriptive. Muscivora is built from the words for fly (musca) and the verb “to devour” (vorare), and forficata is derived from the Latin word for scissors (forfex). The first part of the binomial is the genus name and second is called the “trivial” name because it was, after all, a much shortened version of the complete description.

As Western science closed in on the idea of evolution — that one species could develop from a population of another — binomial names were altered. Muscivora was discarded because it was realized the scissor-tailed flycatcher was a kingbird with a very long tail and so was reassigned to Tyrannus. The phenomenon of evolution means that species within a genus are closely related, and hybrids mean they are so closely related that members of separate species occasionally interbreed where populations overlap.

The lost hybrid flycatcher hanging around a parking lot in Dover seems to have received mixed signals from its mixed genome. It inherited the urge to migrate from its T. forficata parent and now seems at loss as to what to do next. As of this past Wednesday, it was still present in an increasingly un-Texas-like location.

Bill Chaisson has been a birdwatcher from the age of 10. He is a former managing editor of the Eagle Times and now lives and works in the town of Wilmot. Contact him at [email protected].