HARVARD UNIVERSITY
Ernst Mayr Library
of the Museum of
Comparative Zoology
DEC
4 2006
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'S/ry
Y
JUL 2 9
TAXONOMY OP
Y
THE MARSH WREN
m SOUTHERN CALIFORNIA
by
Philip Unitt, Karen Messer, and Marc Thery
No. 31
31 May 1996
Proceedings of the
San Diego Society of Natural History
r
ISSN 1059-8707
PROCEEDINGS :^%^
of the ^^( 2 9
San Diego Society of Natural History
1996
Founded 1874
''^^1^°
Number 31 31 May 1996
Taxonomy of the Marsh Wren in Southern California
Philip Unitt
San Diego Natural Hisloiy Museum. P. O. Box 1390. San Diego, California 92 112
Karen Messer
Departmenl of Mathematics. California State University, Fullerton, California 92634
Marc Thery
Centre Nationale de la Recherche Scientifique, URA 1 1 S3. Museum National d'Histoire Naturelle, Lahoratoire d'Ecologie
Generale, 4 Avenue du Petit Chateau. 91800 Brunoy. France
ABSTRACT. — At least three subspecies of the Marsh Wren (Cistnlluinis /xj/i/.t/n.t) occur in southern California C /) plesimlpuhenus is a widespread
migrant and winter visitor and breeds in the Owens Valley south to Owens Lake It is charactenzed by large size, pale tawny rump and scapulars, a nearly
white breast, mostly brown crown, and bold white back streaks It amves m its winter range mainly in mid to late September and departs mainly in April.
A distinction between plesius and puherius seems likely but was not examined in this study. C. p aestiuinmis is resident from the Colorado River and
Imperial Valley northwest locally through the Mojave Desert, and along the coast from Ventura County north through northern California to southwestern
Oregon. It is charactenzed by its medium size, moderately dark rufous rump and scapulars, a crown partly black and partly brown, and narrow to moderate
white back streaks. Its breast ranges from moderately buff (usually in the Colorado Desert; frequently in the Mojave Desert and along the coast) to deep
buff or brown (usually in the Sacramento Delta; frequently in the Mojave Desert and along the coast) A distinction between aesluannm and deserticola
could be maintained if specimens from the type localities only (Sacramento Delta and Imperial Valley, respectively) were considered, but the area of
intergradation is so large (Mojave Desert, coastal central and northern California) that the distinction does not seem broadly useful
The resident population of coastal southern California (Los Angeles to San Diego counties) is differentiated by its small size, largely black crown,
and deep rufous rump and scapulars At least 94% of specimens of this population can be distinguished from all other Marsh Wren subspecies, so we
propose it be known by the new name Cistolhoni.s paluslris ilarkae.
No California Marsh Wren population agrees with that of southwestern Washington, with its largely dark brown crown, broad brown nape collar, and
consistently narrow whitish streaks on a reduced brownish black back patch That subspecies, paludicola. extends south only to northwestern Oregon
INTRODUCTION ranges in v/idth from practically zero to about 9 mm. The patch
on the back ranges from small and brownish black with obscure
The subspecies of the Marsh Wren (Cistothorus palustns) in whitish streaks to large and completely black with white streaks
California were reviewed most recently by Rea (1986). The fonnat as broad as the black between them. The scapulars, rump, under
of that review (Phillips 1986), however, did not allow a species with tail coverts, and background color of the tail range from me-
variation as complex as the Marsh Wren's to be analyzed as thor- dium buffy brown to deep rufous. The underparts range from
oughly as appropriate. Also, specimens collected over the last ten practically white to mostly buff or brown with only small pale
years now allow that variation to be described more accurately than patches on the throat and in the center of the belly. The variation
was previously possible. Here we attempt to describe the Marsh in size is most easily expressed by wing length.
Wren's vanation as it relates to southern California and to apply the
information to understanding of the species' distribution and migra- HISTORICAL BACKGROUND
tion. Our central goal is to place the resident Marsh Wrens of coastal
southern California within the framework of the species' variation. Ridgway (1904) listed two subspecies of the Marsh Wren for
We also attempt to describe the Marsh Wren's southern California California, the smaller, darker paludicola Baird, 1858, from the
distribution in detail, as this is still poorly understood [e.g., the map "Pacific coast district." west of the Cascade Range and Sierra Ne-
in Zeiner et al. (1990) has many inaccuracies]. vada (type locality Shoalwaler [now Willapa] Bay, Pacific County,
In western North America, various populations of the Marsh Washington), and the larger, ^dXtx plesius (Oberholser, 1897) from
Wren differ in color, pattern, and size. The crown ranges from the "Rocky Mountain plateau district," west to northeastern Califor-
entirely brown to black with only a small brown patch in the nia (type locality Fort Wingate, New Mexico, in the winter range),
center of the forehead. The dark crown patch is separated from Gnnnell ( 1903) first recognized />/f.v;n.v as a winter visitor to coastal
the black and white patch on the back by a brown collar, which southern California.
Philip Unitl, Karen Messer, and Marc Thery
Swarth (1917) described aesluannus, type locality Grizzly Is-
land, Solano County, California, as darker still than paludicola but as
large as plesius. He ascribed to aestuarinus a range extending Crom
Suisun Bay through the San Joaquin delta and valley, with scattered
specimens of migrants trom more coastal localities. Cistothorus p.
paliuiicola he believed resident along California's entire coastline,
extending inland in the lowlands of southern California, though he
cited a few inland specimens from northern California as well.
Grinnell and Miller (1944) followed Swarth (1917) closely, desig-
nating coastal specimens of aestuarinus and inland specimens of
paludicola as migrants. They extended the breeding range of
aestuarinus to the Imperial and Colorado River valleys.
Aldrich (1946) subdivided plesius, describing a duller, less
rufescent subspecies pulverius (type locality Sprague, Lincoln
County. Washington). He ascribed lo pulverius a breeding range from
eastern Washington south to northeastern California and northwest-
em Nevada. The fifth edition of the American Ornithologists' Union
(1957) checklist followed Grinnell and Miller (1944) for the dark
lowland forms but did not distinguish pulverius. Phillips et al. ( 1 964)
took an even more conservative approach, reverting to Ridgway
(1904) in recognizing only one dark lowland subspec\ef,, paludicola,
and one pale plateau subspecies, /)/<\v/h.?. Mon.son and Phillips ( 198 1 ),
however, accepted pulverius and equivocated on aestuarinus.
Not until Phillips (19X6) was the species as a whole revised
again. In this work, Rea contnbuted the characterizations of the dark
lowland subspecies of western Marsh Wrens, while Phillips himself
covered the remainder of the species. Phillips recognized both
pulverius and plesuts, while Rea recognized aestuarinus, segregated
the desert population from aestuarinus as deserlicola, and suspected
the coastal California population to represent an undescribed subspe-
cies, "brighter and richer" than paludicola. aestuarinus, or
deserticola.
Figure 1 shows the general breeding distribution of the Marsh
Wren in western North America, the type localities of the named
subspecies addressed m this study, and the sites in coastal southern
California where Marsh Wrens were collected for this study.
METHODS
Specimen Resources
The taxonomic identity of the Marsh Wrens of coa.stal California
cannot have been adequately assessed previously because of a dearth
of specimens known to represent the local breeding populations.
Migrants of pulverius and plesius, especially the latter, are common
in southern California in winter, and their arrival and departure dates
have not been known precisely.
The ideal specimens on which to base a taxonomic study of the
Marsh Wren should be collected as soon as possible after a complete
molt and therefore with the least worn plumage with its maximum
genetically determined information content. The birds' constant
contact with rough, often damp vegetation wears and stains the
plumage more than in many species. Though in the eastern United
States the Marsh Wren has a complete prealtemate (prenuptial) molt
in spring (Kale 1966). such a molt is not common in the West. Of 1 1
February-May specimens from southern California examined dur-
ing this study, all are too worn to have undergone an extensive recent
molt, and of the three whose molt status was described on their label,
all specified "no molt." Likewise two March specimens from south-
western British Columbia [San Diego Natural History Museum
(SDNHM)] are rather worn and not molting. Of eight May-June
specimens from southeastern Oregon, at least four are too worn to
have molted recently. But three February-March specimens from
Solano County, California (Carnegie Museum of Natural History,
Pittsburgh) are molting their throats, and one of these was replacing
its tail (K. C. Parkes pers. comm.). Since a prealtemate molt in
western Marsh Wrens is rare or at least inconsistent, we based our
study on specimens collected shortly after the prebasic molt, in late
summer or fall.
For the resident Marsh Wrens of southem California, therefore,
the ideal specimens are those collected after the completion of molt
but before the amval of migrants. For such a sample, in 1994 Unitt
mist-netted Marsh Wrens at three sites along the coast of San Diego
County where the species was known to breed. Birds still in juvenal
plumage or heavy molt were released, while those whose molt was
nearly or quite completed were collected and prepared as study
skins. The field work began on 23 August and ended on 7 October,
when pale migrants had cleariy arrived and were outnumbering the
dark local birds. In all, 24 specimens from coastal San Diego County
were collected for this study.
Since 1984. for basic data on land birds' distribution and migra-
tion. Roger Higson and Unitt have been collecting in the Imperial
Valley, southeastern California, whose avifauna has not been studied
in detail. Over 12 years, we have accumulated 33 specimens of the
Marsh Wren, on dates from 4 August to 12 February. This sample
includes both representatives of the local population and migrants
from farther north.
In October 1984 and September 1986, Amadeo Rea, Kem
Hainebach, and Unitt visited Grizzly Island and adjacent Joice Island
in the delta of the Sacramento River, collecting 30 Marsh Wrens
around the type locality of aestuarinus ( 12 in October 1984. 18 in
September 1986). On 12 September 1986. we also took two at Gray
Lodge State Wildlife Area. Butte County.
For a sample of nominate paludicola, we borrowed from the
Burke Museum, University of Washington (UW), 20 specimens
collected in Pacific and Grays Harbor counties, Washington, on 20
September 1985, 18 November 1985, and I and 2 October 1986. To
gain a broader sample from southern California, we borrowed 13
specimens from the San Bemardino County Museum (SBCM), 41
from the Los Angeles County Museum of Natural History (LACM).
4 from the Santa Barbara Museum of Natural History (SBMNH), 2
from the Museum of Systematics and Ecology, University of Cali-
fornia, Santa Barbara (UCSB), and 1 from the Museum of Vertebrate
Zoology, University of California, Berkeley (MVZ).
The sample of specimens on which we base our characterizations
of Marsh Wren subspecies were all collected within the past 15
years. We excluded older specimens because comparison of new and
old specimens revealed obvious foxing of specimens collected in the
first half of the century: among the darker individuals, the rump and
scapulars of all the old specimens were more mfous than the recently
collected ones. Because mmp and scapular color appeared to be an
important variable, and we know of no means for correcting for this
shift, widespread among birds, we used only the recent specimens.
Once the framework was established with the recent specimens, we
used a few older specimens to augment our geographical and histori-
cal perspective.
Character Assessment
The features in which the Marsh Wren varies geographically
differ qualitatively, so they had to be assessed in vanous ways. AH
measurements and visual assessments were made by Unitt.
Wing chord was measured to the nearest 0.1 millimeter Body
size, as reflected in wing length, is the only feature in which the sexes
differ. The mean wing chord of males, in the entire sample of
specimens, was 1 .06 that of females. Therefore, so that the sexes
could be combined in the statistical analysis, we multiplied the
measurements of the females by 1 .06 to yield an adjusted result,
which we used in the remainder of the analysis. In support of this
adjustment, Messer ran a two-way analysis of variance on our
"enlarged" sample (see below under Categorization of specimens for
analysis) with wing length as the response and population of origin
and sex as the explanatory variables. Residual plots showed the data
to be approximately normally distributed; the ratio of the smallest
Taxonomy of the Marsh Wren in Southern Cahfornia
Figure 1 . Approximate breeding distnbution ofthe Marsh Wren in western North Ainenca (shading). In many areas within this range, the species occurs
in only scattered localized colonies. •, type localities of subspecies addressed in this study; ▲. sites in coastal southern California where Marsh Wrens were
collected for this study.
(0.72) to the largest (2.12) standard deviation was less than .^, with
most sample sizes between 10 and 15. The two smallest groups had
standard deviations near I. There was no significant interaction
between the sex effect and the population-origin effect (/> > 0.05),
justifying the use of a single adjustment for sex across all groups.
Had we used the estimated main effect for sex from this analysis in
our adjustment, the factor would have been 1 .077. a change of 1 .6%.
We did not feel this would affect our results materially and retained
the original adjustment for simplicity. A multiplicative rather than
additive factor was used to bnng the females' standard deviation
(2.01 in the enlarged sample) clo.ser to the males' standard deviation
(2.30 in the enlarged sample).
The width of the brown nape collar (between the black of the
crown and the black of the back) was measured to the nearest
Philip Unitt, Karen Messer. and Marc Thery
millimeter. In specimens in which the rear of the crown is brown, the
crown is a darker shade than the nape collar, and in these the
measurement was made from this fairly abrupt transition. The width
of the collar is affected to some extent by the amount to which the
neck IS elongated or compressed when the specimen is prepared. A
few specimens were not scored for this variable because they were
poorly made or had lost neck feathers. The great majority of the
California specimens were prepared by Unitt; preparation by a single
technician enhances uniformity. Nape-collar width is a significant
variable only in comparisons of the broad-collared puhidicola from
coastal Washington with other populations. The sample of paliulicola
consisted of specimens with naturally proportioned necks all beauti-
fully made, largely by C. S. Wood.
The vanation in crown pattern was assessed by ranking each
specimen on a scale from 1 to 6, in comparison to six specimens
serving as standards. In category 1 (standard SDNHM 43970) the
crown is essentially entirely brown, with only a few black feathers at
the sides. In category 2 (standard SDNHM 44592) the crown is
mostly brown, with some black along the sides. In category 3
(standard SDNHM 44532) the black extends around the rear of the
crown as well as along the sides. In category 4 (standard SDNHM
48937) the crown is about half brown and half black. In category 5
(standard SDNHM 48932) the crown is mostly black with some
brown extending from the forehead into the center In category 6
(standard SDNHM 48982) the crown is black with only a .small
brown patch on the forehead.
The variation in back pattern we assessed by ranking each speci-
men on a scale from 1 to 4. In category 1 (standard UW 40570) the
back is brownish black with very narrow dull whitish streaks. In
category 2 (standard SDNHM 43379) the back is deeper black with
whiter but still narrow streaks. In category 3 (standard SDNHM
48992) the back is deep black with white streaks broader than in
category 2 but still narrower than the intervening black streaks. In
category 4 (standard SDNHM 42843) the pure white and pure black
streaks are of about equal width.
The variation in the color of the scapulars and rump and of the
underparts we assessed by two methods. First, Unitt ranked the color
of the scapulars and rump on a .scale from 1 to 10. Category 1
(standard SDNHM 43469) corresponds to a medium tawny brown,
close to color 26, Clav Color, of Smithe ( 1975). Categories 2 (stan-
dard SDNHM 43972) and 3 (standard SDNHM 44592) are .some-
what darker, the latter close to Smithe's color 121C, Mikado Brown.
Category 4 (standard SDNHM 48954) is close to color 223, Verona
Brown. Categories 5 (standard SDNHM 47685) and 6 (standard
SDNHM 43456) are darker yet, the latter close to color 121B,
Brussels Brown. Categones 7 (standard SDNHM 48937) and 8
(standard SDNHM 48938) are a deeper cinnamon-rufous, category 8
being close to Smithe's color 23, Raw Umber. Finally categories 9
(standard SDNHM 4898 1 ) and 1 0 (standard SDNHM 489 1 2) are the
darkest rufous, the latter close to color 1 2 1 A, Front's Brown.
Later, Thery and Unitt measured the retlectance spectrum of
the rump of each specimen in percentage of a Spectralon (Ancal,
Inc.) white standard, using an Ocean Optics, Inc., PSIOOO diode-
array portable spectroradiometer upgraded for near-ultraviolet light
(range 300-800 nm), a bifurcated fiber-optic retlectance probe,
and an Ocean Optics LS-1 tungsten-halogen lamp. To avoid
specular reflectance, measurements with the reflectance probe were
done at an angle of 45" against the feather surface, measuring an
oval spot 3 mm wide. One measurement was made at the center of
the rump for each specimen, as long as the reflectance curve
averaging 5 scans was stable. Reflectance spectra were recorded
between 350 and 700 nm with a resolution of 1 nm. The measure-
ment range includes some near-ultraviolet light that is not per-
ceived by humans but is by many birds. From retlectance curves,
Thery then assigned each recorded spectrum a score for hue (domi-
nant wavelength), chroma (purity or saturation of the color), and
total brightness, computed following Endler (1990).
Our procedure with underpart color was parallel to that for rump
and scapular color. The specimens were ranked among six catego-
ries. In category I (standard SDNHM 43972) the breast is practically
white with a light buff tinge only along the sides. In category 2
(standard SDNHM 44592) a faint buff wash extends across the
breast. Specimens in category 3 (standard SDNHM 47685) have a
distinct buff breast band. In category 4 (standard SDNHM 48912)
the breast is darker brownish buff and the throat is tinged brown. In
category 5 (standard SDNHM 48938) the breast is still darker,
medium brownish. Category 6 (standard SDNHM 43386) represents
the Marsh Wrens with the darkest breasts; the entire underparts are
brown with only a triangular patch in the center of the belly being
whitish. In the darker-breasted specimens collected very shortly after
molt, in September, the underparts are more rufous, whereas in those
from the same locality collected just one month later, in October, the
color has dulled to a drab medium brown. Because this change
appears to result from some adventitious process, the specimens
were ranked for underpart color on the basis of paleness or darkness
alone, not hue.
Again, we evaluated the breast color of each specimen with a
spectroradiometer, placing the sensor over the darkest point along
the midline of the breast. The results were converted into values for
hue, brightness, and chroma in the same way as those for the rump.
Data Analysis
Speciromdiomeiry. A graphical assessment of the spectrora-
diomelnc results for breast and rump color suggested that brightness
was the variable with the greatest (and probably only) systematic
variation. Scatterplots of spectroradiometric assessment versus vi-
sual ranking for rumpAscapular bnghtness and for breast brightness
(Figures 2 and 3) reveal in both cases a positive but only moderate
correlation (Pearson correlations of 0.51 and 0.58, respectively).
Some difference might be expected because the spectroradiometer
measured a range of wavelengths broader than that to which the eye
IS sensitive, but there may be other confounding factors as well.
Because the visual assessments consistently gave better results, we
did not use the speclroradiometnc results further in the analysis.
The reason(s) why the spectroradiometer proved less satisfactory
than the eye in these comparisons are unclear. Endler (1990) dis-
cussed several reasons why the human eye's and brain's perception
of colors is not proportional to the electromagnetic characteristics of
the light reflected from an object and reaching the eye. He recom-
mended the use of spectroradiometers to circumvent this problem.
He did not address, however, other problems that may affect the
applicability of spectroradiometers in taxonomic studies of birds,
where often subtle rather than gross contrasts require quantification
and testing. We suspect that such problems more than the nonlinear
response of the human eye and brain accounted for the mediocre
agreement between the spectroradiometric and visual assessments in
our study. Possibly variation arising from the irregulariy multilay-
ered structure of plumage overwhelmed the rather subtle vanation in
color we were trying to record. Though we tried to ensure that the
sensor recorded only the pigmented tips of the feathers, possibly it
was influenced irregularly by some of the dark gray bases of the
feathers, confusing the results. The sensor read a much smaller area
of plumage than that embraced by the visual assessments; possibly
because of differences of scale the two are not always comparable.
The low retlectance of the rump and the dullness of both the rump
and breast colors may exceed the equipment's sensitivity. Though
spectroradiometry of plumage has been used occasionally in taxo-
nomic studies of birds (e.g., John.son 1980, Atwood 1988), to our
knowledge, the reliability and sensitivity of vanous spectroradio-
meters and various techniques for using them have not been com-
pared and tested. Since more precise and replicable quantifications
Taxonomy of the Marsh Wren in Southern CaHfornia
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< 0.005, but
because of the stepwise procedure used in vanable selection, the
nonnomial nature of several of the variables, and the nonrandom nature
of the samples, it is questionable how much inference may be drawn
from this fact. For similar reasons, we decline to present confidence
regions or prediction regions based on an assumption of normality.
For ease of interpretability in the pairwise compansons, we present
graphs intermsof the pair of vanables that we felt were most useful in
making a visual assessment of the group separation. TTiis is usually the
pair of variables with the strongest univariate group mean separations
(as measured by the F-to-enter test statistics at step 0 in the stepwise
vanable-selection procedure). Occasionally, this pair did not produce
the most obvious .separation, and in that case the pair of vanables that,
considered together, was most informative was used (as measured by
the f-to-entertest statistic at step 1 in the vanable-selection procedure).
In the figure legends, these are described as "the pair of variables in
which (the groups] differ mo,st." While these plots are more easily
interpretable than the corresponding canonical-vanable plots, they do
not separate the groups as well (compare Figures 4 and 1 1 ).
In assessing which characters were most informative in the
pairwise compansons, we again chose to present them in order of
univariate mean group separations, as we felt these would be the
easiest to use visually. Note that this means the first two variables
listed may not be the/jairof most informative vanables but rather the
two variables that when considered in isolation best differentiate the
groups. When we say a pair of populations "differs significantly" in a
variable, we mean the group means differ significantly at /? < 0.05.
The variables actually used in the discriminant function are indicated
by italics. These are the variables that, when the others are already in
use, conlnbute additional information.
Figure 5 Histogram of the canonical variable resulting from a stepwise
discnminant analysis of the core sample of 10 specimens of Cislothorus
patustris plesnislpuheniis and all Marsh Wren specimens from the San
Joaquin delta. The discnminant function was based on the core specimens,
and was used to classify the remaining specimens. Underpart color, rump/
scapular color, wing length, back pattern, and crown pattern, in decreasing
order of importance, are the informative variables. C, core specimens of
plesiuslpuherius: D. core specimens oi aesmarimis. A, inferred specimens of
plesnislpulvenus. B, inferred specimens of aesiuanints.
RESULTS
Cluster Analysis
Cluster analysis of the initial core sample of 65 specimens,
covering all five key populations, identified three well-defined groups
(Figure 6). The sample from coastal San Diego County was the most
distinct; the 10 specimens of plesiuslpulvenus formed a second
branch. Among the remainder of the specimens, the coastal Washing-
Taxonomy of the Marsh Wren in Southern Cahfornia
27.11
plesius/pulverius
paludicola aestuarinus
Observations
s. Calif.
Figure 6. Cluster analysis of the core sample of 65 specimens of the Marsh Wren, covenngall five key populations on which further analyses were based
Letters designate exceptional specimens not clustering with the rest of their population as labeled A, aestuarinus: C. coastal southern California; D.
deserticolu: W, paludicola. The height of the horizontal bar separating each cluster is proportional to the distance between clusters, as measured by Ward's
algonthni The first dichotomy separates all but one of the coastal southern California sample from the remaining specimens; the second dichotomy separates
the Great Basin population [plesius/pulverius) from the remaining specimens. The population of southwestern Washington {paludicola) segregates only
partially from the remaining specimens, from the Colorado Desert (deserlicola) and San Joaquin delta (aestuarinus).
ton (paludicola) and Sacramento Delta (aestiianiuis) samples clus-
tered together but did not segregate clearly from each other, some
paludicola forming a subcluster, others falling with aeslitannus. Of
the three Colorado Desert (deserlicola) two fell among the cluster of
aestuarinus. one with the sample from San Diego.
The sharp distinction of the San Diego sample from the remain-
ing specimens suggested that it be evaluated as a separate group in
the discnminant analyses; we then used the results of these analyses,
both of the entire sample and of comparisons to each other popula-
tion individually, to assess the level of and basis for this distinction.
Discriminant Analysis: All Five Populations Simultaneously
Core sample, deserlicola excluded. The core sample consisted of
specimens that we are certain, on the combined basis of their locations
and dates, to represent one of our five key or "parent" populations,
corresponding to either named subspecies or the resident population of
coastal southern California. Because the core sample included only
three complete specimens of deserlicola. possibly insufficient to de-
fine a discrete group, we ran the analysis both with and without these
three specimens. Discnminant analysis of the core sample containing
only the remaining four groups yielded a function capable of catego-
nzing 58 of the 62 specimens into the four groups defined by their
ongins, for an overall correct classification rate of 94%. The San
Diego and Great Basin samples did not overlap with any other; the
only misclassification was belween paludicola and aestuarinus. When
the classification rates were corrected via the jackknife procedure, the
results differed only in that one specimen from the San Diego sample
and an additional specimen of paludicola were misclassified with
aestuarinus (Table 1 ). From 86 to 100% of each group was classified
as its origin suggested; for each of the four groups this figure exceeds
the 75% traditionally regarded as the threshold for formal taxonomic
recognition, suggesting each of the four may constitute a valid subspe-
cies. A plot of the two most informative canonical variables associated
with the discriminant function (Figure 7) best illustrates the segrega-
tion among the populations, reducing to two dimensions most of the
information from the six variables with which we describe variation in
western Marsh Wrens.
Core sample, deserticola included. A repetition of the discrimi-
nant analysis including the three August/September specimens from
Table 1. Jackknife-corrected discriminant-function classification
of the core samples representing Cislothorus pcdustris plesiusi
pulverius, C. p. paludicola. C. p. aestuarinus. and the population of
coastal southern California.
Number of specimens classified as
plesius/
pulverius
palu-
dicola
aestu-
arinus
Coastal
S Calif
Percent
Correct
C p. plesius/
pulverius
C p paludicola
C. p aestuarinus
Coastal S Calif
10
0
0
0
0
0
100.0
2
0
900
12
0
8.5 7
1
17
94.4
Philip Unitl, Karen Messer, and Marc Thery
3 -
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o o
-5
0
1
5
canonical variable
Figure 7. Scatterplot of the two most informative canonical variables
generated by a stepwise discriminant analysis of the core sample of 62 speci-
mens of the Marsh Wren, covenng four key populations (desertkola excluded).
O. specimens from the Great Basin or inferred to have onginated there [plesiusl
pulvenus). +. specimens from southwestern Washington ljkiludicola).x. speci-
mens from the San Joaquin delta Uiesliuiiiinis), D, specimens from coastal
southern California.
the Colorado Desert did not greatly alter the results among the other
four populations, but the attempt to define a group on the basis of
these three specimens alone was unsuccessful. With the jackknife
procedure, two of the three were classified by the discriminant
function among other groups, while the desert "cluster" attracted one
or two specimens from each of the other groups except plesiusl
pulverius. A plot of the canonical variables implies a tendency of the
Colorado Desert population, despite its marginal position geographi-
cally, to be intermediate among the other four clusters in plumage.
Clearly, a larger sample from the Colorado Desert was necessary for
the taxonomic position of that population to be assessed, and this was
the goal of the following step.
Enlarged sample. We repeated the discriminant analysis, with an
attempt to define five populations, on the core sample augmented as
described above under Categorization of specimens for analysis
(including the 12 October specimens from the San Joaquin delta, all
inferred to represent aestiuinnns. the additional 1 3 and 1 6 specimens
inferred, respectively, from companson of deserticola and plesiusl
pulverius to represent those populations; Figure 4). This analysis of
104 specimens (Figure 8) suggested that all five populations could
be considered subspecies. The poorest distinction was between
aesluannus and deserlicola, but even after jackknife correction the
discriminant function still classified 81% of each of these groups as
expected (Table 2).
Discriminant Analysis: Pairwise Comparisons of Five Populations
Cistolhorus p. plesiuslpulverius vs. paludicola. This pair of popu-
lations differs significantly in all vanables, in order of decreasing
importance, wing length, rump/scapular color, underpart color, back
pattern, nape-collar width, and crown pattern. The discnminant
function revealed a wide separation belween paludicola and the core
sample of plesiuslpulverius. With the enlarged sample of plesiusl
pulverius. the separation was not complete; three specimens fell
within the cluster of paludicola. reducing the rate of correct classifi-
cation in the total sample to 93% after correction for over-
classification via a jackknife procedure. Figure 9, a scatterplot of
plesiuslpulverius versus paludicola in wing length versus rump/
scapular color, reveals these three misclassificd specimens. Possibly,
some of the misclassificd plesiuslpulverius in the enlarged sample,
from the Imperial Valley, were misidentified deserlicola (see above
under Categonzation of specimens). But even if not, the two popula-
tions are differentiated well enough to be continued to be recognized
as subspecies.
Cislothoriis p. plesiuslpulverius vs. aestuarinus. This compari-
son yielded one of the strongest distinctions; the two groups differ
significantly in five of six vanables (all except nape-collar width),
and the discriminant analysis, after jackknife correction, classified
100% of the specimens as expected. Rump/scapular and underpart
color are the two variables most responsible for this separation
(Figure 10).
Cistolhorus p. plesiuslpulverius vs. deserticola. These two groups
differ significantly in four variables I rump/scapular color, under-
part color, wing length, and crown pattern), but in the discriminant
analysis the second two did not add any discriminating power be-
yond the first two. Therefore, in Figure 1 1 we present a scatterplot of
the two groups in just these two variables; this allowed us to include
the two specimens in the core sample of deserticola that were
molting their primaries. In this plot, the groups appear well sepa-
rated, hut, as discussed above under Categorization of specimens
and shown in Figure 4, several fall and winter specimens from the
Impenal Valley bridge the gap. Study of a larger sample of both
subspecies may reveal some overlap not evident with our core
samples. Nevertheless, the strong separation obvious in Figure 11,
and the 1 00% separation achieved by the discnminant function, even
after jackknife correction, implies that any ovedap is not extensive
enough to invalidate the distinction between deserticola and plesiusl
pulverius.
Cistotlwrus p. plesiuslpulverius vs. coastal southern California
Table 2. Jackknife-corrected discriminant-function classification of the en-
larged samples representing Cistolhorus paluslris plesiuslpulverius, C. p.
paludicola, C. p. aestuarinus. C. p. deserlicola. and the population of coastal
southern California.
Number of
spe
cimens c
assified as
Pl
esiusi
palu-
aestii-
deser-
Coastal
Percent
pii
veriiis
dicola
anntis
licola
S. Calif
Correct
C. p. plesiusl
puheriii.s
22
1
0
1
0
91.7
C. p. piiludicola
0
17
2
1
0
85.0
C. p. aestuarinus
0
2
21
3
0
80.8
C. p. deserlicola
0
0
2
1,1
1
81.3
Coastal S. Calif.
0
0
0
1
17
94,4
Taxonomy of Ihc Marsh Wren in Soulhem California
4
3
(N
Id
0
o
• ^1^
c
-1
o
c
a
o
-2
-3
▲
<
A
<
i^
A
A A
<
o
• •P
•
•
A
\l
O
o
o
A
A
A
< <
<1 (
o
o8
•
• •
f
A
1e ■
«p
o
o
^^*
^
t
■ ■
■ ■
-5 0 5
canonical variable 1
Figure 8- Scatterplol of the two inost informative canonical vanables generated by a stepwise discnminant analysis of the enlarged sample of 104
specimens of the Marsh Wren, consisting of the core sample of 65 specimens augmented with 14 inferred specimens of plesius/pulverius. 12 inferred
specimens of aestiuirinus. and 13 inferred specimens of deseriicoUi. •, core-sample specimens of plesius/pulverius: O. inferred specimens of plesiusi
puhenus: H. specimens from southwestern Washington [puludicola): *, core-sample (September) specimens from the San Joaquin delta (aesluarinus):
+. inferred (October) specimens of aesluctnitus from the San Joaquin delta; M, core-sample specimens from the Colorado Desert (desenicohi). 0. inferred
specimens of deserucola from the Colorado Desert; A. core-sample specimens from coastal southern California.
population. Rump/scapular color, wing length, underparl color, and
crown pattern all contributed significantly toward the strong separa-
tion of these two groups. Figure 1 2 is a scatterplot based on the two
strongest vaiiables, rump/scapular color and wing length. Only two
specimens were misclassified by the discriminant function. Both are
inferred specimens oi plesius/pulverius from the Imperial Valley and
not used in the generation of the discnminant function.
Cistolhorus p. paludicola vs. aestuannus. Five variables contrib-
uted significantly toward the differentiation of the Washington and
San Joaquin Delta samples; in order of decreasing importance,
underparl color, nape-collar width, crown pattern, rump/scapular
color, and back pattern. Figure 13, a scatterplot depicting the first
two of these variables, reveals some overlap. Even with all variables
combined in a discnminant function, however, a 100% separation
could not be achieved. Marginal overlap left three specimens of
paludicola and one of aestuarinus on either side of the line of best
separation decided by the discnminant function. Jackknife correc-
tion of the function suggested that 88% of the combined samples
could be assigned correctly. All of the inferred (October) specimens
of aestuarinus were correctly classified. Though the separation is not
total, it appears adequate to support continued recognition of
aestuarinus as distinct from paludicola.
Cistothorus p. paludicola vs. deserticola. Rump/scapular color.
nape-collar width, and back pattern contributed toward a good
separation between this pair of samples (Figure 14). Only one speci-
men was misclassified by the discriminant function, an inferred
specimen of deserticola that by virtue of its rather narrow white back
streaks (rated 2) and rather pale rump (rated 5), and despite its
narrow nape collar (3 mm, outside the range of paludicola), fell in
the middle of the cluster of paludicola as defined by the canonical
vanable generated by the discriminant function. Following the jack-
knife correction, the discriminant function predicted a 97% separa-
tion of these two populations.
Cistolhorus p. paludicola vs. coastal southern California popula-
tion. This pair of samples segregated 1 00%, differing significantly in
all variables, in order of decreasing difference, rump/scapular color,
crown pattern, wing length, nape-collar wuith, hack pattern, and
underparl color. The plot of rump/scapular color versus back pattern
(Figure 15) shows the clearest separation in two variables. The
canonical variable generated by the discriminant function suggested
10
Philip Unitt, Karen Messer, and Marc Thery
2 3 4 5
rump / scapular color
Figure 9. Scatterplot for Cistolhonis pahislns plesiuslpulvenus and C
p. pahulicokt of the two vanahles in which they differ most, vving length and
rump/scapular color So that the sexes could be considered together in one
statistical process, the wing chords of females were multiplied by 1.06, the
factor by which the average male Marsh Wren exceeds the average female
•, core-sample specimens of plesius/putverius; O, inferred specimens of
plesitis/pulverius.M. specimens from southwestern Washington (piitudicdki).
In this and subsequent figures in which one or both of the axes represents a
variable ranked in discrete categones, some "jitter" has been added to avoid
overstnkes and thereby show all points plotted.
not only complete separation but a gap between the two populations
(Figure 16). It is evident that the name pahuiicola does not apply to
the resident Marsh Wrens of coastal southern California.
Cistothorus p. aesluarimis vs. deserticola. Among the 10 pairs of
"parent" populations, this comparison yielded the weakest separa-
tion. The stepwise variable-selection procedure used only a single
variable, underpart color, in the discriminant function. Back pattern
2 3
underparts
Figure 1 1 . Scatterplot for Cisunlumis paluslris plesiuslpulvenus and C p.
deseriicoki of the two vanables in which they differ most, nimp/scapular color
and underpart color 9, core-sample specimens of plesiuslpulvenus, O, in-
ferred specimens oi plesiuslpulvenus; ■ , core (August/September) specimens
of the breeding population of the Colorado Desert (.desenicola): D, additional
October-February specimens from the Colorado Desert inferred as desenicola
(see Figure 4).
is the next most informative variable; its distribution among so few
categories reduces Us contribution to the generation of the discrimi-
nant function. When the function was modified to include back
pattern, however, it placed 3 of the 30 specimens of aestuannus with
desenicola, 1 (not from the core sample of 5 specimens) of the 18
specimens of desenicola with aestiiarinus (Figure 17). Thus a dis-
tinction can be drawn so that only 4 of 48 specimens in the samples
from at or near the type localities overiap, suggesting a valid distinc-
tion between these two subspecies. Application of the discriminant
functions to specimens from elsewhere in California, however, mud-
o
■o 5
•S 4 -
n.
y 3
"d.
E 2
0 12 3 4 5
underparts
Figure 10. Scatterplot for Cislolhorus palustris plesiuslpulvenus and C
p. aestuarinus of the two vanables in which they differ most, underpart color
and rump/scapular color 9. core-sample specimens of plesiuslpulvenus; O.
inferred specimens of plesiuslpulvenus; H , core-sample (September) speci-
mens from the San Joaquin Delta (aesiuarinus); D, additional (October)
specimens from the San Joaquin Delta (inferred aesiuarinus)
10
9
8
7
6
5
4
3
2 H
1
0
CO O ^ (P
*) o© • o • • •
45 50 55
adjusted wing chord
Figure 12. Scatterplot for Cislolhorus paluslris plesiuslpulverius and
coastal southern California Marsh Wrens of the two vanables in which they
differ most, rump/scapular color and wing length. So that the sexes could be
considered together in one statistical process, the wing chords of females
were multiplied by 1 ()6, the factor by which the average male Marsh Wren
exceeds the average female •, core-sample specimens of plesiuslpulvenus;
O. inferred specimens of plesiuslpulverius; ■ , specimens of the breeding
population of coastal southern California
Taxonomy of ihe Marsh Wren m Southern Cahfornia
11
5 -
c« 4 —
a,
(U
T3
3 -
nape-collar width
Figure 13. Scatterplot for Cisiorhonis paluslns pahidicoUi and C. p.
aesluarinus of the two vanables in which they differ most, underpart color
and nape-collar width. A. specimens from southwestern Washington
(paludicola), •, core-sample (September) speciinens from the San Joaqum
Delta (aestuaimus). O. additional (October) specimens from the San Joaquin
Delta (inferred aesuuinnus).
died this distinction substantially, so it does not seem useful on a
broader scale (see below).
Cislollumis p. aestitarimis vs. coastal southern California popula-
tion. The discriminant function analysis, with jackknife correction,
separated these two groups completely, with a substantial gap between
them. Rump/scapular color, wing length, undetpart color, crown pal-
tern, and back pattern, in decreasing order, all differed significantly.
Figure 18, a plot of rump/scapular color versus underpart color, shows
this separation in just two vanables. Evidently, the name aestitannus
does not apply to the Marsh Wrens of coastal southern California.
Cistothorus p. deserticola vs. coastal southern California popu-
lation. The discriminant analysis, from the direct result and after
2 3
back pattern
Figure \^- Scatterplot for Cislalhorus pulustns paludicola and coastal
southern California Marsh Wrens of the pair of vanables in which they differ
most, rump/scapular color and back pattern A, specimens fi-om southwest-
em Washington (paludicola): •, specimens of the breeding population of
coastal southern California.
cross-validation via jackknifing. classified 38 and 37, respectively.
of 39 specimens as expected on the basis of their origins. The
discriminant-function analysis identified four variables as infor-
mative in making this distinction, in order of decreasing impor-
tance, wing length, rump/scapular color, crown pattern, and un-
derpart color. Between this pair of populations, back pattern and
nape-collar width do not differ significantly. Wing length alone
separates the samples totally (with adjustment for sex, the coastal
sample measures 44.0-50.4 mm, the desert sample 50.7-55.9 mm),
though the approach is so close some overlap should be expected in
large samples. Though the two groups differ substantially in rump/
scapular color (only 2 of 1 8 desert specimens rating darker than 7;
only 2 of 1 8 coastal specimens rating paler than 8, and one of these,
collected in February, was likely faded in comparison to the rest of
the sample, collected in August and September), the computer-
o
o
3
o
C/1
11 -f
10
9
8
7
6
5
4 H
3
2
back pattern
Figure 14. Scatterplot for Cistothorus palusiris paludicola and C p.
deserticola of Ihe pair of variables in which they differ most, nimp/scapular
color and back pattern A. specimens from southwestern Washington
[paludicola). •. core-sample (August/September) specimens of the breeding
population of the Colorado Desert (deserticola), O. additional Oclober-Febm-
ary specimens from the Colorado Desert inferred as deserticola (see Figure 4)
20
10
r3
0 -
-13 -12 -11
-10 -9 -8 -7 -6
canonical variable
Figure 16 Histogram of Ihe canonical vanable resulting from a stepwise
discnminant analysis of Cistothorus paluslns paludicola and coastal south-
ern California Marsh Wrens Rump/scapular color, nape-collar width, and
back pattern are the vanables contnbuting to the separation. Shaded bars,
C p. paludicola; white bars, coastal southern California Marsh Wrens.
12
Philip Unitt, Karen Messer, and Marc Thery
5 -
<%
t
4 —
\\
^
•
3 -
^
°&
2 -
1
(TO
1
1
back pattern
Figure 17. Scatterplot for Cixtolhorus paluslris aesluarinics and C. p.
deserlicoki of the only two vanables in which they differ significantly, under-
part color and back pattern A. core (September) specimens from the San
Joaquin Delta (aesluarinus). A . additional (October) specimens from the San
Joaquin Delta (inferred aesniannus); 9. core (August/September) specimens
of the breeding population of the Colorado Desert (deserticdhi), O, additional
October-February specimens from the Colorado Desert inferred as deserticola
(see Figure 4)
generated discriminant function did not use this variable, the infor-
mation it provides being redundant with thai for other variables.
The difference in the crown is the coastal sample's averaging more
extensively black. A slight difference in the underparts arose from
25% of the desert sainple's being rated 2, paler than in any of the
coastal specimens. Figure 19 is a scatterplot of these two groups
showing the separation on the basis of wing length and rump/
scapular color
Two specimens of these groups were misclassified by the dis-
cnminant function. One is SDNHM 42931, the single February
(comparatively worn and faded) coastal specimen, the other SDNHM
46003, an Impenal Valley specimen at the dark extreme for the
species in rump/scapular color (rated 10), a color matched otherwise
10
o
3
Q.
a
o
7 -
6 -
5 -
underparts
Figure 18. Scatterplot for Cistothorus paluslris aestuarimis and coastal
southern California Marsh Wrens of the pair of variables in which they differ
most, rump/scapular color and underpans. •, core (September) specimens
from the San Joaquin Delta Uiesluanmis), O, additional (October) specimens
from the San Joaquin Delta (inferred aesluiinmis), ■, specimens of the
breeding population of coastal southern California
10
9 -
6 -
5 -
47 49 51 53
adjusted wing chord
Figure 19 Scatterplot for Cisunhorus paluslris deserlicoki and coastal
southern California Marsh Wrens of the two vanables in which they differ
most, wing length and rump/scapular color So that the sexes could be
considered together in one statistical process, the wing chords of females
were multiplied by 1 06, the factor by which the average male Marsh Wren
exceeds the average female. ■. core (August/September) specimens of the
breeding population of the Colorado Desert (deseriicola), D, additional
October-February specimens from the Colorado Desert inferred as
desenicola (see Figure 4); •, specimens of the breeding population of coastal
southern California.
only along the southern California coast. In wing length and crown
pattern, however, this specimen is like deserticola and unlike the
coastal sample.
The jackknife-corrected discnminant analysis suggested that only
5% of a sample of these two populations should overlap. Therefore,
the name desenicola does not apply well to the southern coastal
population.
ALLOCATION OF SPECIMENS FROM OTHER SITES
We applied the discriminant functions generated by both the core
and enlarged samples to specimens from elsewhere in the Marsh
Wren's breeding range.
Coos County, Oregon
Of two specimens collected 7. 1 miles north of Coos Bay on 22
October 1982 (SDNHM 42077 and 44078), one was placed by the
discriminant functions (from both the core and enlarged samples)
with deserticola, the other with aesluarinus. That neither was placed
with paludicola suggests that the southern limit of paludicola lies
somewhere along the coast of central Oregon and does not reach
California.
Humboldt County, California
A single immature male (SDNHM 3203), collected at Clam
Beach on 18 October 1967, is older than the specimens on which the
discriminant functions were based but we assessed it anyway, as it was
still in heavy molt so presumably represents the local population. With
a rump/scapular rating of 7 and a crown rating of 4, it is at the pale
extreme for the southern California coastal population, but its short
wings (apparently fully grown in at 48.8 mm) are typical of that group,
to which the discriminant functions assigned it. With the exception of
one specimen from the Imperial Valley, it is the only specimen from
outside coastal southern California placed with that group.
Taxonomy of the Marsh Wren in Southern Cahfornia
13
Coastal Central California
Another somewhat aged specimen (SDNHM 35175), collected
18 September 1958 just northeast of Martinez in Contra Costa
County, has paler underparts (rated 3) than the sample from just 10
miles to the northeast across Suisun Bay at Joice and Grizzly islands
(all rated 4 or 5). Therefore, it matches deserticola better than
aeslitannus, and that is where the discriminant functions placed it.
An old, foxed specimen (SDNHM 24642), collected 4 December
1938 at Santa Cruz, though not evaluated by the discrimrnani func-
tions, appears closest to deserticola as well. The breast is only lightly
tinged buff, while the crown is too brown and the wings loo long
(50.7/51.7 mm, female) for the southern coastal population.
A specimen from the mouth of Los Osos Creek on Morro Bay,
San Luis Obispo County, collected 7 September 1986 (SDNHM
44461), was placed with aestuarinus by the discriminant function
based on the core specimens alone, with deserticola by the function
based on the enlarged sample. Of two specimens (SBMNH) from
Dune Lakes, southwestern San Luis Obispo County (28 September
1962, 12 September 1973). the former was placed by the discnmi-
nant functions with deserticola. the latter with aestuarinus. Of two
specimens from the Santa Ynez River mouth. Santa Barbara County
(UCSB). one (4 January 1992) is clearly a rmgxxAplesiuslpulverius.
while the other (10 January 1992) was placed by the discnminanl
functions with aestuarinus. Though the base for drawing a conclu-
sion is rather meager, evidently the Marsh Wrens of coastal central
California bridge the difference between aestuarinus and deserticola.
Oases of Mojave Desert
We examined specimens from two sites in the Mojave Desert.
Harper Dry Lake, San Bernardino County, and Piute Ponds, Los
Angeles County.
The specimens from the Piute Ponds, within Edwards Air Force
Base in the Antelope Valley, are all in the Los Angeles County
Museum. Five were collected on 27 October 1989. Of these, two are
migrant plesiuslpulverius. while the other three fit with deserticola.
Six were collected in spring, from 26 April to 8 May. Three are
juveniles; two are badly worn adults. One adult, a male with enlarged
testes taken 26 Apnl 1989. is still in a condition good enough to be
assessed. It agrees well with deserticola in all variables.
From Harper Dry Lake, we assessed 17 specimens, all collected
in fall and early winter, the earliest fall specimens being taken on 28
September All were therefore taken at a time when migrants should
be expected, and. not surprisingly, of the 17. 6 were identified by the
discriminant functions as plesiuslpulverius. Two additional speci-
mens (SBCM), identified by the functions as paludicola, were prob-
ably migrants from the Great Basin as well. One had a rump/scapular
score of 2, typical for plesiuslpulverius but not (or paludicola. With
nape-collar widths of 5-6 mm, probably their necks were elongated
in preparation in compan.son to the specimens used in the defining
samples, as they were made by different preparators. The other 9
Harper Dry Lake specimens are too dark on the rump, scapulars, and
underparts for the migratory subspecies, so we infer these represent
the resident population. Of the 9, 5 conform with deserticola. while
1 (SBCM 53683), with a nape-collar width of 5 mm and a back score
of 2, was placed by the functions with paludicola. Again, this
specimen may have had its neck overly stretched; in other variables
it agrees with deserticola. Three specimens, by virtue of their darker
underparts (especially striking in SDNHM 48952) or narrower back
streaks, better fit aestuarinus. Though it is possible that these appar-
ent aestuarinus dispersed southeast from the Central Valley, more
likely they represent normal variation in the resident population. The
dark extreme of underparts crops up in one specimen of deserticola
from the Imperial Valley, and the narrower white back streaks (rated
2) in two specimens. As noted above, the distinclion between
aestuarinus and deserticola is comparatively weak, and despite the
wide separation of the main ranges, the intervening oases may
provide an opportunity for gene flow. Even in these nonmigratory
subspecies, substantial dispersal ability likely favors survival of
birds dependent on widely scattered tiny patches of suitable habitat.
Ventura County, California
Unfortunately, we located only a single recent specimen from
Ventura County, a male taken at the sewage ponds in the Point Mugu
military reservation on 13 December 1986 (SBMNH 5090). This
specimen falls within the range of the southern coastal population in
its fairiy dark rump and scapulars (rated 7) and fairly blackish crown
(rated 4) but disagrees in its long wings (53.4). The discriminant
functions placed it with deserticola.
SUBSPECIES DEFINITIONS
These comparisons suggest that plesiuslpulverius, paludicola,
aestuarinus, and the population of coastal southern California are all
differentiated at a level appropriate for designation as subspecies.
Cistothorus p. deserticola presents a more awkward problem.
Cistothorus p. plesiuslpulverius
Our analyses reaffirm the distinctiveness of the more or less
migratory plateau population from the lowland populations nearer
the Pacific Coast, a difference universally recognized since 1897.
This group is identified by its comparatively long wing (a difference
expected between migratory and sedentary populations), entirely
brown to moderately black crown (Figure 20), narrow brown nape
collar, broadly white-streaked back, comparatively pale tawny rump
and scapulars, and pure white or only slightly buff-tinged breast
(Figure 21). In combination these features sufficed to distinguish
92% of our sample.
Assessing the distinction between plesiits and pulverius was not a
goal of this study, and such an assessment was not possible from the
sample used, which lacked specimens from the breeding range of
plesiids. The few specimens from eastern California were among the
largest and palest of the sample, however, suggesting the Marsh Wrens
breeding along the east side of the Sierra Nevada and Cascade Range
(pulverius) represent the extreme development of this group's charac-
ters and may be distinguishable from the majority of winter visitors in
southern California, in which these characters are on average less
extreme and may be migrants from farther east in the Great Basin/
inlermountain region (plesius). The greater abundance of apparent
plesiiis in winter in southern California, despite its breeding range's
being more remote, may be due to a difference between pulverius and
plesius in the winter climate of the breeding range. From the Pacific
Ocean to the Rocky Mountains, winter temperatures tend to decrease
from west to east, and wintering by Marsh Wrens in the ranges of
pulverius and plesius has been reported as irregular and dependent on
iheseventy of the winter (e.g.. Root 1988; Gilliganet al. 1994).
Cistothorus p. paludicola
The sample from southwestern Washington stood apart from the
others largely on the bases of its entirely brown to only slightly black-
margined crown, broad brown nape collar, and nartowly white streaks
on a reduced weakly black-tinged back patch. TTie rump/scapular
ranking of pahuhcola overlapped extensively with those of aestuarinus
and deserticola on our light-to-dark scale, but the hue of these parts of
the p]umage paludicola tends more toward an earth brown, and away
from rufous, than in the other lowland subspecies, a subtle variation
not captured in our analyses but evident in Figure 20. In wing length
and underpart pattern paludicola occupies a position intermediate with
and overiapping several other populations. The weakest separation of
paludicola was from aestuarinus, but the darker underparts, blacker
14
Philip Unite, Karen Messer. and Marc Thery
clarkae
pahidicola
deserticola
plesius
aestuarinus
pulverius
Figure 20 Upperparts of six populations of the Marsh Wren CisUHlwnis paluslns clarkae. based on SDNHM 48915, holotype from Batiquitos Lagoon,
Carlsbad, San Diego County, Cahfomia, 23 August 1994 C /> desenicola (best included under aesuiariims). based on SDNHM 44278, a topolype from 2
miles north-northwest of Seeley, Impenal County, California, 29 September 198-'>. C p. aesnianniis. based on SDNHM 445.^2, virtual topotype from Joice
Island, Solano County, California, 9 September 1986 C /> paludicola. based on UW 40S65, a topotype from the North River mouth, Willapa Bay, Pacific
County, Washington, 18 November 1985 C /> plesius. based on SDNHM 43971, from Picacho Reservoir, Pinal County. Anzona, 24 October 1985. C. p.
pulverius. based on SDNHM 4.3469, from Owens Lake, 5 miles northeast of Olancha, Inyo County, California, 20 September 1984.
Taxonomy of the Marsh Wren m Soulhcrn Cahlorni;
15
clarkae
paliidicola
deserticola
plesius
aestimrmus
pulverius
Figure 21. Underparts of six populations of the Marsh Wren, based on the same specimens as in Figure 20
16
Philip Unitt, Karen Messer, and Marc Thery
crown, narrower nape collar of the latter still served to allow 91% of
that pair of populations to be distinguished.
Cistothonis p. aestuarimis
The Sacramento Delta sample differed from the other groups
primarily on the basis of its dark underparts; the specimens ranked
darkest (5) on the underparts were from this area almost exclusively.
In wing length, rump/scapular color, crown pattern, nape-collar
width, and back pattern the delta sample was in an intermediate
position, as might be expected from its central position geographi-
cally. The extreme developments of some of the peripheral popula-
tions, however, plesius/pulveriiis in large size and plumage paleness,
paliidicola in its broad nape collar and brown crown, and the popula-
tion of coastal southern California in its small size and dark upper-
parts, left aesluarinus adequately isolated from these. The distinc-
tion from deserlicola. on the basis of darker underparts and narrower
white back streaks alone, was the weakest but could be defined so
that only 4 of 43 specimens from near the type localities in the
combined enlarged samples overiapped with the other.
Cislothonis p. dcsi'iticiila
Despite its peripheral position geographically, the population of the
Colorado Desert is the least distinctive morphologically. In all charac-
ters, it lies in a position intermediate among the other subspecies. It
differs from plesius/pulveriiis in its tendency toward a darker rump and
scapulars, buffier underparts, shorter wings, and blacker crown. It
differs from paludicola in its tendency toward darker rump and scapu-
lars, a narrower nape collar, ;ind bolder white back streaks. It differs
from aestnarmus in its tendency toward paler underparts and narrower
white back streaks. Its differs from the population of coastal southern
California in its longer wings, tendency toward paler rump and scapu-
lars and browner crown, and average slightly paler breast.
If only the type localities oi aesluarinus and deserlicola had to be
considered, the two subspecies could be recognized fairly easily. But
the samples from coastal central California and Harper Dry Lake
show the whole range of these phenotypes. A distinction between the
two implies a biogeographically oddly shaped zone of intergradation
at least as large as the core ranges of the subspecies. Therefore,
recognition of deserlicola as distinct from aesluarinus doei not seem
practical, a result implied also by the group's failure to segregate in
the cluster analysis.
The wide range (even to south-coastal Oregon) of Marsh Wrens
matching the characters of deserlicola suggests that the deserlicola
phenotype could represent the primitive appearance of California's
lowland Marsh Wrens and that the dark underparts of aesluarinus are
an innovation that arose in or near the San Joaquin Delta and has
spread to some degree over most of California but has barely touched
the southeastern corner of the state. Conversely, the aesluarinus type
may have originally been widespread, and, especially before the
damming of the Colorado River and irrigation of the Imperial Valley,
deserlicola was confined largely to the Colorado Delta. Changing
water-management practices have probably increased the range and
population of deserlicola enormously in historic time (Rosenberg et
al. 1991), possibly enabling it to invade northwest and mix with
aesluarinus.
Southern California Coastal Population
The sample from San Diego County was well isolated from the
others on the basis of having the shortest wing, most extensively
black crown, and darkest rump and scapulars. In nape-collar width,
back pattern, and underpart pattern it did not differ greatly from
several other samples, overlapping in those features substantially.
But the sample stands at the extreme for the species in three of the six
characters quantified in this study. Cluster and discriminant analyses
consistently identified it as an independent group. In all discnminant
analyses, both pooled and pairwise, 91% or more of this sample was
classified as expected on the basis of origin, while no more than 6%
of any other sample was classified with the San Diego group, even
when the discriminant functions were cross- validated via jackknif-
ing. Because the level of differentiation of this sample well exceeds
the 75% threshold, and equals or exceeds that of other subspecies
recognized in the Marsh Wren, we propose that it be known as
Cistothorus palustris clarkae subsp. nov.
Holotype. San Diego Natural History Museum number 48915,
collected by Philip Unitt (original number 1357) on 23 August 1994
at the east end of Batiquitos Lagoon, city of Carisbad, San Diego
County, Califomia (35" 06' N, 117" 16' W). Adult female (skull
completely pneumatized; ovary granular, 4 x 1.5 mm; ova minute).
Weight 8.1 grams; slight fat. Length in flesh 123 mm, wingspread
1 56 mm, wing chords 47. 1 mm. Prebasic molt completed except for
a few feathers on chin and face.
Diagnosis. Differs from other western populations of the Marsh
Wren in small size (see Table 3), more extensively black crown (at
least 50% black; usually with only a small brown patch in the center
of the forehead), and darker rufous scapulars, rump, upper tail
coverts, and central rectrices, in fresh plumage all of these close to
Raw Umber or Prout's Brown of Smithe (1975).
The new subspecies differs from deserlicola, as suggested by
jackknife-adjusted discnminant analysis, at a 94% level (at least) by
these three characters, plus a slight tendency to a darker breast. A
single exceptionally dark specimen of deserlicola and a probably
laded February specimen of clarkae were the only two confounding
specimens. In the sample examined wing length alone yielded 100%
separation.
From aesluarinus, clarkae differs at a nearly 100% level by its
usually darker rump and scapulars, shorter wing, paler underparts
and flanks (breast pale buff), and blacker crown. In combination
these characters distinguish 100% of specimens from the type local-
ity. From the broader range of aesluarinus, as we redefine it, includ-
ing all of coastal California south to Ventura County and the Mojave
and Colorado deserts (deserlicola), only 2 of 60 specimens (3%)
were placed by the discriminant functions with clarkae.
From paludicola, with which it has traditionally been linked,
clarkae differs al a 100%> level by its bolder white back streaks on a
blacker background, and narrower brown nape collar (2-7 mm in
clarkae. >5 in only 2 of 23 specimens; 4—9 m paludicola, <5 in only
3 of 20 specimens) in addition to the three other characters.
From the migratory plateau subspecies pulverius and plesius,
which invade its range in fall and winter, clarkae differs even more in
the three main characters than it does from the other lowland popula-
tions, plus it has a more intensively buff breast. From the Marsh
Wrens of northeastern North Amenca Uamgi, iliacus, dissaeplus,
and nominate paluslris), clarkae differs in its barred upper tail
coverts as well as its darker rump and scapulars and buff breast band.
From the Marsh Wrens of the coastal southeastern United States
clarkae differs as follows; from lliryophilus by its largely blackish
crown, from marianae and waynei by its more rufous rump and
scapulars and lack of dusky speckling or barring on the flanks or
breast, and from griseus by its far more rufous rump and scapulars
and more extensive black and white patch on the back. From
lolucensis of central Mexico clarkae differs by its less extensive
black and white back patch and paler, less rusty underparts.
Dislnbulion. Coastal lowland of southern California, from the
Tijuana River immediately north of the Mexican border north to Los
Angeles. Of 25 old October-February Marsh Wrens from Los Ange-
les and Orange counties in the Los Angeles County Museum of
Natural History, 22 appear to be migrants of plesius/pulverius, while
Taxonomy of the Marsh Wren in Southern California
17
Table 3. Wing chords of various subspecies of the
Marsh Wren.
Standard
n
Mean
Range
Deviation
Males
C. p. plesiusi
puherius
II
.S4.9
51.0-57,1
1.93
C. p. paludicola
16
51-3
49.5-52.4
0.70
C p. uestuanmis
15
51.4
49.5-53.3
0.97
C. p. deserticola
5
52.4
51.7-53.8
0.81
C. p. clarkae
12
48.2
44.0-50.4
1.84
Females
C. p. plesiusi
pulverius
13
50.3
48.2-52.2
1.16
C. p. paludicola
4
46.4
45.3-48.2
1.09
C. p. aestiiaritnts
12
48.0
46.5-51.3
1.36
C. p. deserticola
II
49.0
47.8-52.7
1.39
C. p. clarkae
12
45.6
43.3^7.1
1.09
3 agree with clarkae in their extensively black crowns (rated 5 or 6),
dark (now foxed and unscorabie) rump and scapulars, and short
wings (46.2 in the one female; 44.7 and 48.2 in the two males). These
are LACM 12289, from the San Gabriel River on 23 December
1895, LACM 2376, from Nigger Slough on 12 February 1918, and
LACM 17629, from Play a del Rey on 20 December 1931. These
specimens demonstrate that the characters of clarkae are long estab-
lished in this population, not an artifact or innovation of the recent
sample from San Diego County.
The breeding Marsh Wrens of western Riverside County prob-
ably belong with clarkae. though this needs confirmation with recent
specimens. The only specimen we have seen from this area, SBCM
3912, is a migrant plesius collected 12 March 1967. For further
details and historical changes, see below.
One specimen implies short-distance dispersal of clarkae across
unsuitable habitat. This is LACM 1 9635, a male collected by George
Willett on 13 November 1939 on San Clemente Island, where the
Marsh Wren is only a rare nonbreeding visitor (Jorgensen and
Ferguson 1984). The rump is as dark as in the three old specimens of
clarkae from Los Angeles County. The crown seems to have lost a
few feathers so is difficult to judge but looks about half black. At
only 48.0 mm. the wing measurement is typical of clarkae.
Etymology. We name this Marsh Wren in honor of Mary Hollis
Clark, in appreciation of her 33 years of support and service, through
good times and bad, to the San Diego Natural History Museum and
its scientific and educational mission. With the help of Mrs. Clark
and her family, many San Diegans have increased their appreciation
of the uniqueness of their natural environment. With its narrowly
restricted range, Cistolhonis palustns clarkae reveals itself as yet
another element of that uniqueness.
Discussion. Our results confirm Rea's (1986) conjecture that the
coastal southern California Marsh Wrens constitute a subspecies,
though not quite on the basis that he suggested. As noted above, the
pigment coloring the rump and scapulars of Marsh Wrens is subject to
foxing, increasing its redness. Evidently, the greater the concentration
of this pigment, the more grossly the specimen foxes. In the pale
extreme of the species {pulverius) the difference is slight; in the dark
extreme (clarkae) the difference is great, as seen in companson of our
1994 specimens with the three collected in Los Angeles County from
1895 to 1 931. The rump and scapulars of old specimens, in which the
natural darkness of clarkae has been foxed into rustiness. look
"brighter and richer" (Rea 1986) than in the other subspecies.
Swarth (1917) noticed that the Marsh Wrens of coastal southern
California were exceptionally small but did not quantify the differ-
ence. Neither he nor subsequent revisers applied this variable to the
population. The difference in crown pattern has not been reported
previously.
Revelation of an undescribed subspecies of bird in a region as
heavily populated as coastal southern California, which has been
studied by thousands of biologists, may seem incongruous. In the ca.se
of Cistothorus palustris clarkae, however, several factors contributed
toward concealing it for so long. In existing collections, the great
majority of specimens of the Marsh Wren from coastal southern
California were taken in winter, and consist largely of migrants from
the plateau region. Since there is .substiuilial variation among these
migrants, probably interpretable as two subspecies, the additional
variation arising from the few specimens of clarkae was less notice-
able. Some individuals of paludicola and aesluarinus were thought to
make long-distance migrations, reaching coastal southern California,
for which we have seen no evidence. The few breeding-season speci-
mens (e.g., SBCM 36797, Nigger Slough, Los Angeles County, 13
May 19l7)are in poor condition, often with wom crowns, faded rumps
and scapulars, and broken primary tips; they do not preserve well the
defining features of clarkae evident in fresh plumage. The very urban-
ization of the range of clarkae discourages collectors from working in
it; collecting birds at most sites in coastal southern Califomia where
Marsh Wrens breed now requires special authorizations beyond the
standard permit from the Califomia Department of Fish and Game.
DISTRIBUTIONS OF THE SUBSPECIES
OF THE MARSH WREN IN SOUTHERN CALIFORNIA
Cistothorus p. plesiuslpulverius
Marsh Wrens from the Great Basin/intermountain plateau region
winter throughout southern Califomia, invading many areas where the
species does not breed. Though Garrett and Dunn ( 1981 ) reported the
Marsh Wren as absent from the "colder northern deserts" in winter, T
Heindel (pers. comm.) finds it more common in the Owens Valley m
winter than in summer West of the Sierra Nevada, Gnnnell and Miller
(1944) reported plesius north only to Tomales Point and Petaluma.
Mann and Sonoma counties. Gabrielson and Jewett (1940) did not
report it from west of the Cascade Range in Oregon, but in Jewett's
collection (SDNHM) are three specimens, from Taft. Netarts. and
Portland, that conform with the intenor population well in both color
and size. The specimen from Portland (6 October 1928, SDNHM
24646, wings 55.5/56.0 mm) apparently represents the northwestem-
most documented point of these migrants' dispersal.
Understanding of the schedule of arrival and departure of plesiusi
pulverius in southern Califomia needs further refinement. We have
not seen any specimen eariier than one taken for this study in the
Tijuana River valley, San Diego County, on 23 September 1994
(SDNHM 48983). But the migration unquestionably begins some-
what earlier than this; M. Heindel (pers. comm.) finds Marsh Wrens
migrating commonly through the desert oases of eastern Kem County
by 10-20 September; M. A. Patten (pers. comm.) has earliest dates
for migrants in the California deserts of II and 17 September;
Lehman (1994) reported migrants as fairly common in Santa Bar-
bara County by the beginning of September Marsh Wrens have been
reported away from breeding sites as early as 29 August in eastern
Kem County (M. Heindel pers. comm), 14 August in San Diego
County (Unitt 1984), and 23 July in Santa Barbara County (Lehman
1994). We suspect the few early records represent short-distance
dispersal from breeding sites nearby and that migrants from the
plateau region do not reach the coast of southern California until
around the middle of September. But the exact schedule and possible
annual variations of this arrival remain uncertain, requiring testing
via further collecting.
Spring departure takes place largely in April. We have not seen
specimens of plesiuslpulverius from the winter range later than 13
Apnl (1923, salt marsh at Santa Catanna Landing, 29" 30' N, Baja
18
Philip Unilt, Karen Messer. and Marc Thery
•O Santa Barbara
Ventura
O \ Los Angeles
San Bernardino