Taxonomy and Nomenclature

Taxonomy (sometimes called "systematics") is the science of classifying organisms. The Linnean system of classification, used for both plants and animals, was developed more than two centuries ago by the great Swedish botanist Carolus Linnaeus (born Carl von Linné). It is a hierarchical system -- that is, each organism belongs to a series of ranked taxonomic categories, such as a subspecies, species, genus, family, etc. At any rank (level) in the hierarchy any organism can belong to only one taxon, or taxonomic group. For instance, the Yellow-rumped Warbler can be a member of only one genus and one class. Each taxon is given a formal, latinized name that is recognized by scientists around the world. Nomenclature is a formal system of names used to label taxonomic groups.

Birds compose the class Aves, which is in the phylum Chordata (Chordata also includes mammals, reptiles, fishes, and tunicates -- everything with an internal skeletal rod called a "notochord," which in vertebrates is enclosed in cartilage or within a backbone). The living (nonfossil) members of the class Aves are placed into more than two dozen orders, such as the Passeriformes (perching birds), Piciformes (woodpeckers, etc.), Columbiformes (pigeons and doves), Procellariiformes (albatrosses, petrels, etc.), Apodiformes (swifts and hummingbirds), and so on. The orders are divided into about 160 families -- an average 6-7 families per order. Family names can be recognized because they all end in "idae." For example, in the order Passeriformes are such families as the Tyrannidae (the tyrant flycatchers), the Laniidae (the shrikes), and the Emberizidae, a large family that includes, among others, the wood warblers, sparrows, blackbirds, and orioles.

Families, in turn, are divided into subfamilies, with names ending in "inae." The wood warblers make up the subfamily Parulinae and the black-birds and orioles are the Icterinae. Within subfamilies, tribes (name ending "ini") are often recognized: blackbirds are the Agelaiini and orioles the Icterini within the Icterinae. The next commonly used category is the genus: the Yellow-rumped Warbler is in the genus Dendroica, along with more than two dozen very similar species. Its latinized specific name is Dendroica coronata, made up of the name of the genus combined with a trivial name to distinguish it from congeners (other members of the same genus).

Because the Linnean system features a two-part specific name, it is often referred to as a system of "binomial nomenclature." Often, as in this book, the name of the author who first described and named the species in the scientific literature is added to the specific name -- thus, Dendroica coronata (Linnaeus). Traditionally, generic and specific names are set in italic type, and in some works the name of the author is put in parentheses if he or she originally placed the species in a different genus. Thus if you find the Yellow-rumped Warbler listed as Dendroica coronata (Linnaeus), it is because Linnaeus originally placed it in the genus Motacilla, not Dendroica. We have not followed this procedure, since most bird species have long since been moved from their original genera as the taxonomic system has been refined.

Finally, subspecies may be recognized with trinomial nomenclature -- by adding a third name to the specific name. Thus the eastern Yellow-rumped Warbler (formerly the Myrtle Warbler) is Dendroica coronata coronata Linnaeus, and the western Yellow-rumped Warbler (formerly Audubon's Warbler) is Dendroica coronata auduboni Townsend.

The taxonomic-nomenclatural system is a device for communicating about the complexly interrelated products of evolution. Generally it works well, even though many aspects of it are arbitrary. For example, whether Dendroica is distinct enough to be recognized as a full genus, or should be merged with Vermivora and Parula is not self-evident, and ornithological taxonomists disagree on it. Some taxonomists are "lumpers" and would like to combine the three; others are "splitters" and wish to keep them separate. Furthermore, as new studies of the relationships of various higher categories are published, scientists must modify the taxonomic system, and as a result names of taxonomic groups may change, as may the organisms included in them. For example, recent DNA-DNA hybridization studies have led some scientists to conclude that the Emberizidae should be considered a subfamily (Emberizinae) of the family Fringillidae, the wood warblers a tribe (Parulini) of that subfamily, and both the orioles and blackbirds combined in yet another emberizine tribe, Icterini, with the tribal name Agelaiini disappearing.

Changes in latinized specific names are inevitable as knowledge about birds increases, and most should simply be accepted as the price of progress. Common names, at least within North America, show more stability and facilitate regional communication. But for worldwide communication, the level on which professional ornithologists often operate, the latinized names are essential. One need only note that the "robin" in North America is Turdus migratorius, while in England it is Erithacus rubicula (which, in turn, is "roodborst" in Holland, "rotkehlchen" in Germany, "rödhake" in Switzerland, and "rougegorge" in France). An American birdwatcher told by a traveling friend returning from Europe that she had added the "Ring Ousel" and "Blackbird" to her life list might be left pretty much in the dark. But if the American knew that those birds were Turdus torquatus and Turdus merula, he or she would at least know that both were sizable thrushes.

SEE: Species and Speciation; Birds, DNA, and Evolutionary Convergence; Passerines and Songbirds; Superspecies; Sibling Species.

Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.