Subject: Re: Are there standardized definitions?
Date: Feb 4 14:58:42 1996
From: Burton Guttman - guttmanb at elwha.evergreen.edu



Maureen Ellis asked for "the standardized correct use for the following
terms in differentiating birds: Race, morph, phase, population,
subspecies, variant, form." I'll reply to the whole gang, in case some
people disagree with me.

_Population_ refers generally to all the individuals of one species living
in one area, but it is vague because "area" has no set limits. If the
area has a distinct boundary, as an island does, the limits are more
obvious, but since birds are so mobile one can rarely set definite limits
on a population.

_Subspecies_ and _geographic race_ both mean a geographically limited
subdivision of a species that is morphologically distinct from other such
groups. Classically, there has been a "75 percent rule," meaning that a
population may be designated a distinct subspecies if 75 percent of its
members are clearly distinguishable from "all" the individuals of
neighboring populations. The subspecies concept is made difficult
because some species vary clinally; that is, they form a _cline_ in which
features change gradually along some geographical axis, so there is no
place to draw a sharp line between populations. It's also made difficult
by the whole species concept; those who adhere to a biological species
concept won't have much difficulty with it, but those who prefer a
phylogenetic species concept might.

_Morph_ is a morphologically distinct form within a population, but one
that is common enough to not be just an odd, rare mutant. The red and
gray morphs of Screech Owls or the blue and white morphs of Snow Geese are
classic examples--or, for that matter, people with different colors or
hair or eyes.

_Phase_ is a term that was used to mean "morph," but I believe its use is
being discouraged now. _Variant_ means, well, a variant: an albino, for
instance, or an individual with some other aberrant morphology. _Form_
could mean anything, and it's probably another term that should not be used.

If anyone disagrees with these definitions, let's meet in a marsh
somewhere and have a good knock-down, drag-out argument.

Burt Guttman guttmanb at elwha.evergreen.edu
The Evergreen State College Voice: 360-866-6000, x. 6755
Olympia, WA 98505 FAX: 360-866-6794