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Papers in Ornithology Papers in the Biological Sciences
1961
Evolutionary Relationships among the North American Mallards Evolutionary Relationships among the North American Mallards
Paul A. Johnsgard
University of Nebraska-Lincoln
, pajohnsgard@gmail.com
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Johnsgard, Paul A., "Evolutionary Relationships among the North American Mallards" (1961).
Papers in
Ornithology
. 62.
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EVOLUTIONARY RELATIONSHIPS AMONG THE
NORTH AMERICAN MALLARDS
PAUL A. Jo•X•SG.•
This study is the report of an attempt to understand the evolutionary
relationships existing within a group of mallardlike ducks native to North
America. The group includes the Common Mallard, `4nas platyrhynchos
platyrhynchos L.; the Black Duck, `4nas rubripes Brewster; the Florida
Duck, `4nas fulvigula fulvigula Ridgway; the Mottled Duck, .4nas fulvi-
gula macuIosa Sennett; the Mexican Duck, .4nas diazi diaxi Ridgway;
and the New Mexican duck, .4nas diazi novimexicana Huber. All but
one of these (the Common Mallard) are restricted to North America,
and all these American forms possess a sexually nondimorphic plumage.
In all other respects they are extremely similar to the Common Mallard,
and a study of their relationships to this form was believed possibly to
provide an instructive example of speciation.
REVIEW OF RANGES, POPULATIONS, AND NOMENCLATURE
The Mexican and New Mexican Ducks
In 1886 Ridgway described a new species of mallard (.4nas diazi)
from Puebla, Mexico, which, similar to the then recently (1874) de-
scribed Florida Duck, differed from the Common Mallard (`4nas platy-
rhynchos) in its lack of sexual dimorphism. According to Ridgway, the
new species differed from the Florida Duck in its more Mallardlike
characteristics, namely the distinct band of white on the secondary wing
coverts and its less-fulvous over-all coloration. Thirty-six years later,
Huber (1920) described another species of mallard from New Mexico,
which he named `4nas novimexicana. Huber was seemingly unaware of
the similarities shown by the New Mexican Duck to the Mexican Duck,
but in 1922 Conover referred to an extralimital Nebraskan specimen as
.4has dia•i novimexicana, and Phillips (1924) treated the New Mexican
Duck in the same manner in his monograph. Although the close rela-
tionship between the New Mexican and the Mexican ducks was there-
fore realized relatively early, the paucity of specimens and field observa-
tions made the exact geographic relationship between the two forms
uncertain. In 1946 Lindsey summarized the situation as follows: "The
known nesting range of the New Mexican Duck is confined to a small
area of the south-western United States, but the presumptive range
extends southwards into Chihuahua, Mexico, where its relation to the
northern breeding limits of the Mexican Duck (.4. diazi diazi) is unde-
terrained."
Published in the Auk (1961) 78. Copyright 1961, University of California. Used by permission.
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4 J Olt NSGARD, Relationships among Mallards [ Auk
ß I. Vol. 78
ARIZONA i 4G : NEW MEXICO
! ' :8 4G TEXAS
........
j .
.... , •, '•,
',
SINALOA )---" ,[ ( '
• '•. /•--- •.-. • ,.•-
"-•'-, ..• ,/ '• ,,
) ß ( ,' :, '.,
,• ZACATECAS ,-"' ,
Sight Specimen Range
M ex•c•In Duck O ß ,.r-•
(inc) New Mexicofi")
Mottled Duck O ß • __
O 50 I00 I•0 20<) •0
JALISCO •. •
OL So•ulo ?
MICNOACAN
An attempt has been made to map the geographic ranges of the
Mexican and New Mexican ducks, and thus to help visualize their geo-
graphic relationships. This was done by plotting all available specimen
records and such sight records as appeared justified from the literature,
personal communications, and the major United States collections. The
Published in the Auk (1961) 78. Copyright 1961, University of California. Used by permission.
http://elibrary.unm.edu/sora
Auk 1 Jon•-sg^Ru, Relationships among Mallards 5
Vol. 78 J
resulting map (Figure 1) shows fairly close agreement with thc com-
parable maps of Dclacour (1956), Arcllano and Rojas (1956), and
Leopold (1959). It follows the map of Leopold in indicating an unbroken
range bct;vccn the New Mexican and Mexican populations, although
records arc spotty for the area in question. If birds at the northern parts
of the range arc migratory, for which there is some evidence, it is probable
that they winter in the heart of the range of diazi; habitat conditions arc
very poor on the Chihuahua lakes, and they arc unattractive to waterfowl
(Saunders and Saunders, 1949).
Of all the races of North American mallards, perhaps least is known
about the Mexican Duck, and this is certainly the case regarding the
total population size. Since 1947 the U.S. Fish and Wildlife Service
has surveyed the lakes of interior Mexico during its annual January
waterfowl inventories. Mr. R. H. Smith, who has flown this route each
year since 1951, has provided (in litt.) the data obtained for the Mexican
Duck during these years. The sinailest total number of Mexican Ducks
recorded was 780 in 1951, and the largest total was 10,322 in 1958.
Although the northern Chihuahuan lakes--Toronto, Bustillos, and Mexi-
canos--•vere surveyed, it is of interest that no Mexican Ducks have been
recorded there; Lago Santiaguillo, Durango, is apparently the northern
wintering limit of the Mexican Duck in Mexico. Its western limit would
appear to be Lago Sayula, Jalisco, and the eastern limit in the 1natshy
region near Oriental, Puebla. These data would indicate that the size
of the adult Mexican Duck population is probably less than 20,000 birds.
New Mexican game biologists have estimated that the population in their
state is extremely snmll, possibly not over 100 adult birds.
The Florida and Mottled Ducks
In 1874 Ridgway described a new form of mallard from St. Johns,
Florida, which he considered to be a subspecies of the Black Duck. As
the Black Duck was at that time called Anas obscura, the new bird was
named Anas obscura var. fulvigula. It differed mainly from the Black
Duck in that the malar region, chin, and throat were immaculate buff
rather than streaked with dusky, and the plumage had a general
ochraceous, rather than dusky, tone. At the time it was known only
from Florida. Later (1878) Ridgway relegated it to the rank of a full
species, Arias fulvigula. Eleven years later, Sennerr (1889) described
from Texas yet another species of mallard, which he called .4has
maculosa. Sennett stated that the most marked differences between
zt. )•ulvigula and A. maculosa were the latter's streaked, rather than plain
buff, cheeks and a green, rather than purple, speculum in addition to a
mottled, rather than streaked, general coloration. The Mottled Duck
Published in the Auk (1961) 78. Copyright 1961, University of California. Used by permission.
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6 Joa•s•^RD, Relationships among Mallards [ .•.uk
[Vol. 78
was added to the A.O.U. Check-list in 1890 as Anas Iulvigula •naculosa,
and no later arguments for retaining the specific status of maculosa have
been presented.
Although Phillips had vacillated earlier between accepting and reject-
ing the Mottled Duck and Florida Duck as distinct races, in 1924 he
synonymized the two forms. Later, Peters (1931) accepted •naculosa
as being distinct from Iulvigula, although Delacour and Mayr (1945)
as well as Hellmayr and Conover (1948) synonymized them. The form
•J, aculosa is still accepted by the A.O.U. Check-list.
Regardless of the question of the validity of the described plumage
differences, which will be discussed later, a definite hiatus in the ranges
of the populations seems to exist. The range of the Florida Duck (see
Figure 2, which is modified from Howell, 1932, and Sprunt, 1954) is
largely confined to the southern half of peninsular Florida, with its
northern limits being in the vicinity of Gainesville. There are appar-
ently no specimens of fulvigula or maculosa that have been taken in
Mississippi. A single specimen has been taken in Alabama (Imhof,
1958) and may represent either fulvigula or •nacuIosa. In addition,
several sight records along the coast of Alabama have been obtained for
Florida or Mottled ducks. Mottled Ducks occur commonly almost to
the eastern border of Louisiana (Oberholser, 1938). They are found
mainly in the coastal tier of parishes of Louisiana (Lowery, 1955) west
to the Texas border, and in Texas likewise follow the coastal counties
for the entire length of the state (Singleton, 1953). The range of the
Mottled Duck also extends a long distance into Mexico (Saunders, 1952,
1953) in the states of Tamaulipas and Veracruz. The range map pre-
sented in Figure 2 is a composite of information from the sources cited
above, and from additional sight and specimen records available to me.
The Florida Game and Fresh Water Fish Commission has taken a
census of the Florida Duck population annually since 1948 by the aerial
transect method. During the years 1948 to 1955, the estimated total
adult population varied from 17,000 to 30,000 (Sincock, 1957). The
1956 and 1957 inventory estimates for the entire state were 9,000-16,000
and 7,000-10,000 birds, respectively, indicating, according to Sincock, a
sharp drop in Florida Duck numbers in recent years. A reasonable esti-
mate of the present total adult Florida Duck population would appear to
be 10,000.
In Louisiana, inventories of the Mottled Duck population have been
made yearly since 1952. Estimates in recent years have averaged about
10,000 birds (M. M. Smith, in litt.), which are spread out fairly evenly
over the marshes of southeast and southwest Louisiana, being especially
Published in the Auk (1961) 78. Copyright 1961, University of California. Used by permission.
http://elibrary.unm.edu/sora