Like all organisms, species of birds are grouped into hierarchical
categories. In theory, these categories help illustrate evolutionary
relationships. Although this basic classification system was developed in
the 1700s by Linnaeus, a Swedish scientist who described many North
American species, it is still being changed today as new discoveries are
made and recent advances in DNA technology illuminate relationships among
groups of birds. Starting from the highest level, the categories are:
Because the system is hierarchical, the highest levels contain the
largest numbers organisms, related by the most general characteristics. As
you reach the lower levels, fewer kinds of organisms share the more
specific characteristics that define the group. Of course, because
scientists like to quibble, there are many divisions of the basic
categories, for instance superorders, subfamilies, etc.
For birds, the taxonomy would be:
All birds are in the same kingdom, phylum, and class. At the next level,
order, the birds begin to diverge. For instance, the loons are in the
order Gaviiformes while the pelicans and cormorants are in the order
Pelecaniformes. Next comes the family, with the pelicans in the family
Pelecanidae and the cormorants in the family Phalacrocoracidae. At the
genus level, the pelicans are in the genus Pelecanus. At the species
level, there are the American White Pelican, Pelecanus erythrorhynchos,
and the Brown Pelican, Pelecanus occidentalis. The scientific
names are all in Latin so that scientists around the world can communicate
in a common language.
The species is considered the basic biological unit. It is defined as a
potentially interbreeding group comprising various populations that are
reproductively isolated from other such groups. However, even within
species there are sometimes discernible subunits, which are called
subspecies. An example would be the Northern Flicker. In the eastern
United States, it is called the Yellow-shafted Flicker because of its
bright yellow areas under the wings and tail. In western flickers, these
areas are red rather than yellow, and the bird is appropriately called the
Red-shafted Flicker. In the areas where the ranges of the two overlap,
considerable interbreeding results in hybrids between the two. The
Yellow-shafted Flicker is given the name Colaptes auratus auratus
while the Red-shafted Flicker is Colaptes auratus cafer. They are
considered to be the same species but are recognizably different. In the
species lists, subspecies that are recognizably different will be
mentioned. For example, the Red-shafted Flicker is called Colaptes a.
cafer where the a. stands for auratus. The Yellow-
shafted Flicker, the nominate form, is referred to as Colaptes auratus.
Sometimes, two closely related species hybridize. Such is the case with
the Golden-winged and Blue-winged Warblers. Since their offspring have
characteristics of both parents and are easily identifiable in the field,
they are mentioned in the lists as Vermivora chrysoptera x pinus,
where the x indicates hybridization.
The nomenclature used in the BBS Home Page follows The AOU Checklist of
North American Birds(Seventh edition, 1998), with supplements published in
The Auk in July of odd-numbered years.