Fine
question, Jerry (in Chicago).
As brief
background, in 2011 the American Ornithologists' Union (AOU) voted down a
measure that would have split Yellow-Rumped Warbler into two, three or four
species*.
Many of
you already know the Yellow-rumped Warbler currently occurs as four subspecies
(according to many researchers): the “Myrtle” group (coronata), and the
“Audubon’s” group (auduboni), “Black-fronted” (nigrifrons), and “Goldman’s”
(goldmani)
The taxonomy
of these Yellow-rumped Warbler subspecies was under consideration in 2011 for
change by an AOU committee and, currently, is not under consideration for a
status change by this committee (according to my "sources").
(NOTE #1: In the N.A. Birds Online account
for this species, the following additional subspecies is described in the
"Myrtle group (below photo)": Yellow-rumped Warbler
subspecies: D. c. hooveri (McGregor, 1899). This subspecies
breeds in central and s.-central Alaska, se. Alaska, Yukon Territory,
Mackenzie, and nw. British Columbia; intergrades with auduboni known
from Stikine River, AK (Gibson and
Kessel 1997). Like nominate coronata, slightly larger,
with longer wing (minimum wing length 73.5 mm in females, 75.5 mm in
first-year.
(Audubon's
Yellow-rumped subspecies appears in photo, below.)
males, and 78.0 mm in adult males); more streaked
below (Alternate-plumaged males) or paler brown (females). Characters broadly
clinal where range meets that of nominate coronata; for this
reason, hooveri not recognized by Hubbard (1970).
More recently, hooverimaintained as valid (Godfrey 1986, Gibson and
Kessel 1997, R. Dickerman and P. Unitt pers. comment.
NOTE #2: The IOC splits two subspecies in this
group and recognizes Audubon's and Myrtle as two species).
(* = The AOU vote was 7–4 against any divisions of
the Yellow-rumped complex. The committee members suggested the need for further
genetic analysis and determination of the extent of interbreeding in the
subspecies’ contact zones where the “Myrtle” group (coronata), and the
“Audubon’s” group (auduboni) mix in western Canada. The status of two other
subspecies — “Black-fronted” (nigrifrons), and “Goldman’s” (goldmani) remain
unchanged.
Black-fronted is a resident in Mexico, and
Goldman’s occurs only in southernmost Mexico and Guatemala. Neither of these
two subspecies has been observed in the American Birding Association geographical
area.)
As for why, the IOC considers the Myrtle and
Audubon's to represent two distinct species, the following 10 naming rules
appear to guide the IOC's reasons for adopting name choices, with one or more
the reason why the IOC divides the Yellow-rumped Warbler into two species:
Myrtle Yellow-rumped Warbler and Audubon's Yellow-rumped Warbler:
1.
Each
species should have one name only >>
2.
A
species name must be unique >>
3.
Anglicized
names are acceptable >>
4.
Established
names should prevail >>
5.
Local
names should not have priority >>
6.
Offensive
names should be changed >>
7.
Patronyms
are acceptable without bias for or against >>
8.
Simplicity
and brevity are virtues >>
9.
Use
of the word “island” will be limited >>
10.
Species
in the same genus may have different group names >>
