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Journal ArticleDOI

Wintering Distribution Changes in Mallards and Black Ducks

01 Oct 1961-American Midland Naturalist-Vol. 66, Iss: 2, pp 477

AbstractThrough the use of data compiled by the Audubon Society's annual Christmas Counts, an attempt has been made to trace the distributional changes of wintering Mallards and Black Ducks in the eastern states from 1900 to the present. During this period the Black Duck has increased relative to the Mallard in few if any states (the Great Lakes region), whereas the Mallard has increased nearly everywhere else (except in the extreme northeast), particularly in the southern coastal states. Deforestation and changes in land use are suggested as probable reasons for this trend, which is not likely to be reversed. Although several rather spectacular shifts in the distributions of various American species of birds have become evident in recent years, the "colonization" of the eastern states by the Mallard (Anas platyrhynchos) has not been so generally recognized. The magnitude of this range extension has been great nevertheless, and the probable reasons for it have been discussed elsewhere (Johnsgard, 1959, 1961). Concomitant with the increase of the Mallard in the eastern states, the native Black Duck (Anas rubripes) has suffered a decline in numbers, and apparently for some of the same reasons as the Mallard has increased. Since this trend is not likely to be reversed in the future, it will be of interest o follow it carefully and thus possibly to predict the fate of the Black Duck. Wing (1943) became interested in the ratios of Mallards to Black Ducks throughout he eastern states before the range shift was at all apparent, and calculated state ratios for the two forms on the basis of the data provided by the annual Audubon Society Christmas counts for the forty years 1900 to, 1939. He found that the average ratios for that period (which, because of the continuously increasing number of counts, is probably typical of the situation somewhat after the midpoint of 1920) indicated that the zone of equal ratios fell in a northsouth line between Michigan and western Florida. East of this line the Black Duck was markedly dominant over the Mallard and west of it the Mallard was equally dominant. Wing's data are presented in Table I, but they are converted from simple Mallard: Black Duck ratios to the alternative method of calculating the relative percentages of each form in the combined sample. This latter means of presenting ratio data has certain statistical advantages (Hickey, 1957). Arguments supporting the use of these data as unbiased estimates of wintering Mallard and Black Duck populations have been presented elsewhere (Johnsgard, 1959), and so will not be repeated here. To test the possibility that these counts might indicate the degree to which the Mallard has moved eastward in recent years, it was de477 Johnsgard in American Midland Naturalist (October 1961) 66(2). Copyright 1961, University of Notre Dame. Used by permission.

Topics: Anas (56%)

Summary (1 min read)

Introduction

  • The "colonization" of the eastern states by the Mallard (Anas platyrhynchos) has not been so generally recognized.
  • He found that the average ratios for that period (which, because of the continuously increasing number of counts, is probably typical of the situation somewhat after the midpoint of 1920) indicated that the zone of equal ratios fell in a northsouth line between Michigan and western Florida.

478 THE AMERICAN MIDLAND NATURALIST 66(2)

  • Cided to bring these calculations up to date, by collating the Christmas Count records for the twenty years 1940 to 1959.
  • The data for the years 1940 to 1949 show some interesting differences from Wing's data for the preceding forty years.
  • Of the states east of the Michigan to western zone, one state exhibits a majority of Mallards in the wintering population.
  • Eighteen states exhibit marked declines in Black Duck ratios from those presented by Wing.
  • On the other hand, the northern interior states have undergone less pronounced decreases, such as, for example, Michigan, Illinois, Indiana and Ohio.

484 THE AMERICAN MIDLAND NATURALIST 66(2)

  • Mallard gene pool and through the constant reduction of its breeding habitat, may eventually disappear as a distinct entity from their fauna.
  • -This study was done at Cornell University under the support of fellowships from the Cornell University Graduate School and the National Science Foundation.
  • Evolutionary relationships among the North American mallards.
  • Evolutionary relationships among the North American mallards.
  • Relative distribution of Mallard and Black Duck in winter.

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University of Nebraska - Lincoln University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln
Papers in Ornithology Papers in the Biological Sciences
1961
Wintering Distribution Changes in Mallards and Black Ducks Wintering Distribution Changes in Mallards and Black Ducks
Paul A. Johnsgard
University of Nebraska-Lincoln
, pajohnsgard@gmail.com
Follow this and additional works at: https://digitalcommons.unl.edu/biosciornithology
Part of the Ornithology Commons
Johnsgard, Paul A., "Wintering Distribution Changes in Mallards and Black Ducks" (1961).
Papers in
Ornithology
. 72.
https://digitalcommons.unl.edu/biosciornithology/72
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authorized administrator of DigitalCommons@University of Nebraska - Lincoln.

Wintering Distribution
Changes
in Mallards
and Black Ducks
PAUL A. JOHNSGARD
Department of Zoology,
University of Nebraska,
Lincoln
ABSTRACT: Through the
use of data compiled
by the Audubon
Society's
annual Christmas Counts,
an attempt
has been made to
trace
the distributional
changes of
wintering Mallards
and Black Ducks
in
the eastern
states from 1900
to the present.
During this period
the
Black Duck
has increased relative
to the Mallard
in few if any
states
(the Great
Lakes region),
whereas the Mallard
has increased
nearly
everywhere
else (except in the
extreme northeast),
particularly
in the
southern coastal states. Deforestation
and changes
in land use are
sug-
gested
as
probable reasons
for this trend, which
is not likely
to be
reversed.
Although
several rather
spectacular shifts
in the distributions
of
various American
species of birds
have become
evident in recent
years,
the
"colonization" of the eastern
states by
the Mallard (Anas
pla-
tyrhynchos)
has not been so
generally recognized.
The magnitude
of
this
range
extension has been
great
nevertheless,
and
the
probable
reasons for it
have been discussed
elsewhere
(Johnsgard, 1959,
1961).
Concomitant
with the increase
of the Mallard in the eastern
states,
the native
Black
Duck
(Anas
rubripes)
has suffered a decline in
num-
bers, and apparently
for
some
of the same
reasons
as
the
Mallard has
increased.
Since this
trend
is
not likely
to be reversed
in
the
future,
it will be of
interest to
follow it
carefully
and
thus
possibly
to
predict
the
fate of the
Black Duck.
Wing (1943)
became
interested
in the ratios
of
Mallards
to Black
Ducks
throughout
the eastern
states
before the
range
shift was at
all
apparent, and
calculated state
ratios for
the two forms on the basis
of
the
data
provided
by
the annual
Audubon
Society
Christmas
counts
for
the
forty
years
1900 to,
1939. He found that the
average
ratios
for
that
period
(which,
because of the
continuously
increasing
number
of counts, is probably typical
of the
situation somewhat
after
the
mid-
point
of
1920)
indicated
that
the
zone
of
equal
ratios fell in a
north-
south line
between
Michigan
and
western
Florida.
East
of this
line
the
Black
Duck
was
markedly
dominant
over the Mallard and
west
of it the
Mallard was
equally
dominant.
Wing's
data are
presented
in Table
I,
but
they
are converted
from
simple
Mallard:
Black
Duck
ratios to the
alternative
method
of
calculating
the
relative
percentages
of
each form
in
the
combined
sample.
This
latter means
of
presenting
ratio
data
has certain
statistical
advantages
(Hickey,
1957). Argu-
ments supporting
the
use of these data
as unbiased estimates
of winter-
ing
Mallard
and Black Duck
populations
have been
presented
else-
where
(Johnsgard,
1959),
and
so
will not be
repeated
here.
To
test
the
possibility
that these counts
might
indicate
the
degree
to
which the Mallard
has moved eastward in recent
years,
it was
de-
477
Johnsgard in American Midland Naturalist (October 1961) 66(2).
Copyright 1961, University of Notre Dame. Used by permission.

478
THE AMERICAN
MIDLAND NATURALIST
66(2)
cided
to
bring
these
calculations
up
to
date,
by
collating
the
Christmas
Count
records
for
the
twenty
years
1940 to
1959.
Since the
numbers
of
counts
and
counters
has
increased
enormously since
1940,
the
data
were divided
into
earlier
(1940-1949)
and
later
(1950-1959) periods.
Again,
although
the
averages
for these
total
periods
are
presented
(Table
I),
they
probably
reflect the
existing
conditions
somewhat
after
the
mid-points of
the
periods.
It must
be remembered too
that
changes in
the ratios
can
be attributed both to
Mallard increases
in
the
East and
to Black
Duck
decreases,
rather
than
only
to
Mallard
increases
alone.
The
data
for the
years
1940
to 1949
show some
interesting dif-
ferences
from
Wing's
data
for the
preceding
forty
years.
Of the
states
east
of
the
Michigan
to western
Florida
zone,
one state
(Florida)
exhibits
a
majority
of
Mallards
in
the
wintering
population.
Fourteen
states
exhibit
what
are
probably
significant
reductions
in
the
percent-
ages
of
Black
Ducks,
with the
most
marked
changes
occurring
in
Florida,
North
Carolina,
and
Michigan.
Only
four
states
(Wisconsin,
Kentucky,
West
Virginia
and
Virginia)
exhibit noticeable
increases
in
Black
Duck
ratios; of
these
West
Virginia's
data are
probably
not
based
on
a
sufficient
sample.
Since
Wing's
(1943)
data did not
in-
clude
information
on
sample
size
it is
impossible
to
evaluate
these
differences
statistically.
The data for the
years
1950 to 1959
bring
to
light some
even
more
striking
changes.
Five
states
(Florida,
Georgia,
South
Carolina,
North
Carolina and
Ohio) east
of
the
Michigan-western
Florida
zone ex-
hibit
majorities
of
Mallards in the
samples.
Eighteen
states
exhibit
marked declines in
Black
Duck
ratios from
those
presented by
Wing.
Only
two
states
(Minnesota
and
Wisconsin)
exhibit
significant
in-
creases in
Black
Duck
ratios
over
those
of
preceding
years.
To
provide
a
relatively
up-to-date
picture
of the
situation,
data
for the
years
1958
to 1960
are also
presented
in
Table
I.
Although
in
some
cases
the
sample
sizes
are
too
small
to
be
useful,
in
most
a
still
greater
decrease
in
Black
Duck
ratios is
evident.
It is
astonishing
to
contemplate that
in
twenty
years
Delaware,
for
example, has
un-
dergone
a
shift
in
ratios
from
an
almost
pure
Black
Duck
population
to one in
which
Mallards
are
more
abundant
than
Black
Ducks.
Other
only
slightly
less
remarkable
examples
are
provided
by
the
coastal
states
from
North
Carolina to
Florida.
On
the
other
hand,
the
north-
ern
interior
states
have
undergone
less
pronounced
decreases,
such
as,
for
example,
Michigan,
Illinois,
Indiana
and
Ohio. If
a
line
de-
lineating
the
zone of
equality
between
Mallard
and
Black
ratios
were
to
be drawn
today,
it
would
still
have
to
pass
through
Michigan
at
the
north,
but
be
deflected
eastward
to
the
south
so as
to
pass
through
Virginia
and
North
Carolina.
Only
in
Maine
and
the
Canadian
maritime
provinces
may
the
wintering
population
still be
considered
"pure"
Black Duck.
It
appears,
therefore,
that
the
Mallard
has
been
invading
the
East
by a
"flanking"
movement
along
the
Gulf
Coast
states.
It is
hard to
determine
how
rapidly
the
Mallard
has
colonized
Johnsgard in American Midland Naturalist (October 1961) 66(2).
Copyright 1961, University of Notre Dame. Used by permission.

1961
JOHNSGARD:
DUCK DISTRIBUTIONAL
CHANGES
479
TABLE
I.-Relative
numbers
of wintering Mallards
and Black
Ducks,
based on
Audubon
Christmas
Counts from
1900-1960
State
or Province Total
Total
Per
cent
Black Ducks Mallards
Black Duck
Nova
Scotia
1950-1959
5,962
2 99.97
1958-1960
1,865
1 99.95
Quebec
1940-1949
2,092
81
96.27
1950-1959 6,314
155
97.60
1958-1960
1,821
50 97.33
Ontario
1900-1939
97.51
1940-1949
9,370
1,450
86.59
1950-1959
15,163
7,936
65.36
1958-1960 7,261
3,793
65.69
Maine
1940-1949 1,773
2
99.89
1950-1959 6,543
43 99.35
1958-1960
5,102
29
99.43
New
Hampshire
1950-1959 5,791
171
97.13
1958-1960 1,736
234
88.12
Vermont
1940-1949
272
11
96.11
1950-1959
538
12
97.82
1958-1960
170
5
97.14
Massachusetts
1900-1939
99.28
1940-1949 78,570
472 98.52
1950-1959 117,499 7,002
94.37
1958-1960 53,679 4,606
90.38
Rhode
Island
1900-1939
99.35
1940-1949
18,468
101
99.45
1950-1959
18,759
410
97.86
1958-1960 6,800
221
96.85
Connecticut
1900-1939
94.31
1940-1949
19,398
577
97.11
1950-1959 39,802
13,646
74.47
1958-1960
15,269
8,838
63.34
New
York
(entire
state)
1900-1939
96.12
1940-1949 135,376
13,426
90.97
1950-1959
202,713
30,563
86.90
1958-1960
65,891 14,417
82.05
Johnsgard in American Midland Naturalist (October 1961) 66(2).
Copyright 1961, University of Notre Dame. Used by permission.

480
THE AMERICAN
MIDLAND
NATURALIST
66(2)
TABLE I.-
(continued)
State or Province Total
Total
Per cent
Black Ducks
Mallards
Black Duck
New
York
(Long Island)
1940-1949
78,172
4,990
94.00
1950-1959 125,489
13,711
90.15
1958-1960
43,530
7,276
85.68
New
York
(rest
of
state)
1940-1949
57,204
8,436
87.15
1950-1959
77,224
16,852
82.09
1958-1960
22,361
7,141
75.79
New
Jersey
1900-1939
....
.-.
99.17
1940-1949 50,305
3,922
92.76
1950-1959
226,744
28,631
88.79
1958-1960
104,640
10,542
90.85
Pennsylvania
1900-1939
.. ...
95.39
1940-1949
63,933
9,953 86.52
1950-1959 90,307 55,738
61.83
1958-1960
20,456
21,043
49.29
Delaware
1900-1939
......
99.08
1940-1949
21,777
634
97.17
1950-1959
118,489
85,175
58.18
1958-1960
31,288
42,432
42.44
Maryland
1900-1939
. .-...-
94.08
1940-1949
23,309
3,108
88.23
1950-1959 102,184
60,343
62.87
1958-1960
43,482
30,719
58.60
Washington,
D.C.
1940-1949
1,854
376
83.14
1950-1959 7,619
2,170
77.83
1958-1960
1,717
449
79.27
Virginia
1900-1939 ..
....
67.53
1940-1949 15,557 2,599
85.67
1950-1959
68,736
31,259
68.74
1958-1960
26,531
13,706
65.94
North
Carolina
1900-1939
.
90.13
1940-1949
3,133 1,831
63.10
1950-1959 28,830 29,522
49.41
1958-1960
16,849
16,593
50.38
Johnsgard in American Midland Naturalist (October 1961) 66(2).
Copyright 1961, University of Notre Dame. Used by permission.

Citations
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Journal ArticleDOI
TL;DR: Radio telemetry was used to monitor the winter survival and cause-specific mortality of 227 female American black ducks captured in New Jersey and Virginia, 1983-85 to estimate survival rates and examine variation in survival rates during winter in relation to age, body condition, time, geographic location, and weather conditions.
Abstract: We used radio telemetry to monitor the winter survival and cause-specific mortality of 227 female American black ducks (Anas rubripes) captured in New Jersey and Virginia, 1983-85. Mean survival rate for 19 December-15 February was 0.65. Survival from hunting and nonhunting risk was 0.84 and 0.78, respectively. Causes of nonhunting mortality included predation and emaciation (winter stress). After-hatchyear (AHY) ducks had a higher probability of survival than hatch-year (HY) ducks (0.73 vs. 0.60); most of this difference was related to survival from nonhunting risk. After-hatch-year ducks with body masses > median had a higher survival probability (0.85) than AHY ducks with < median body masses (0.61) because of differential survival from hunting risk. Hatch-year ducks had lower body mass than AHY ducks, but among HY ducks body mass was not related to survival. There were no consistent patterns in survivorship in relation to mean daily temperature, although the timing of the onset of low temperatures and storms may have influenced movement patterns. Our estimated survival rates are consistent with estimates from other studies of seasonal and annual survival. It may be possible to manage habitats for population segments at high risk (HY and low body mass birds), and increase black duck survivorship. J. WILDL. MANAGE. 53(1):99-109 Populations of American black ducks have declined from the 1950's to present (Barske 1968, Grandy 1983, Feierabend 1984). Reasons for the decline are unknown but may be related to specific causes of mortality such as hunting (Blandin 1982, Krementz et al. 1988), predation (Ringelman and Longcore 1983), competition from and hybridization with mallards (Anas platyrhynchos) (Johnsgard 1961, 1967), and habitat losses (Barske 1968). Winter is a critical time for black ducks, because of high energetic demands (Albright 1981, Reinecke et al. 1982). Reinecke et al. (1982) demonstrated that immature females achieved adult structural size, but were lighter in weight and had smaller nutrient reserves than did adults during their first winter. Other studies have corroborated a link between age, body condition, and probability of survival. Hepp et al. (1986) reported that the probability of being shot by hunters for mallards in poor condition was higher than for those in better condition. Haramis et al. (1986) reported a direct relationship between the body mass of canvasbacks (Aythya valisineria) in early winter and probability of surviving the winter. Although immature black ducks are more vulnerable to hunting (Schierbaum and Foley 1957, Krementz et al. 1988), and have lower annual survival rates than do adults (Blandin 1982, Krementz et al. 1987), whether age-specific mortality persists through winter, or occurs primarily during the postfledging period and early hunting season is unknown. Managers need estimates of winter survival rates and identification of mortality sources to understand black duck population dynamics and assist in the management of black duck populations. Our objectives were to estimate survival rates of black ducks during winter, examine specific components of mortality, specifically hunting versus nonhunting mortality, and examine variation in survival rates during winter in relation to age, body condition, time, geographic location, and weather conditions. We appreciate the assistance of E. L. Derleth, N. Dietz, B. Dirks, B. L. Estel, S. Holzman, A. G. Larochelle, J. M. Morton, H. H. Obrecht III, S. R. Perin, N. Phelps, H. G. Russell, M. A. Spoden, J. M. Walsh, and G. Wright in the collection of field data. We also thank F. Ferrigno, New Jersey Fish and Game, G. L. Inman and D. L. Beall of Forsythe National Wildlife Refuge, and D. Holland of Chincoteague National 'Present address: Georgia Cooperative Fish and Wildlife Research Unit, School of Forest Resources, University of Georgia, Athens, GA 30602.

130 citations


Journal ArticleDOI
TL;DR: Examination of courtship and pair formation of a wintering population of American black ducks and mallards near Ottawa, Ontario, indicated that initially drakes of both species exclusively courted and paired intraspecifically, and a scenario for black duck-mallard hybridization is proposed.
Abstract: Investigation of courtship and pair formation of a wintering population of American black ducks (Anas rubripes) and mallards (A. platyrhynchos) near Ottawa, Ontario, indicated that initially drakes of both species exclusively courted and paired intraspecifically. After all female mallards had paired, the remaining mallard drakes joined black duck courtship groups. Of the 33 unpaired black duck females remaining at this time, only 27% formed intraspecific pairs, whereas 73% selected mallard drakes as mates, despite there being an excess of black duck drakes. Based on these results, a scenario for black duck-mallard hybridization is proposed. It involves ecological factors including the male-biased sex ratio in northern wintering populations, artificial feeding, and roost-site limitation. Other behavioral aspects, such as the earlier pair formation in mallards and the superiority exhibited by mallard drakes when competing for black duck females are discussed. J. WILDL. MANAGE. 48(3):846-852 One factor essential to a species' genetic integrity is its continued reproductive isolation from congenerics through geographic, habitat, or behavioral means (Lack 1971). Two species of dabbling duck, the American black duck and the mallard, are similar both morphologically and behaviorally, and their hybrids appear to be as viable and as fertile as the parental species (Johnsgard 1961). However, geographic range and evolved habitat differences have until recently deterred hybridization between these two species. Prior to 1900, the black duck and mallard were geographically isolated. Heusmann (1974) examined the evolutionary history of the black duck and hypothesized that it evolved during the Pleistocene glacial period when a population along the eastern coast of North America became isolated from western mallard populations. Habitat differences further segregated these populations as the black duck began breeding in the forested regions of the east and the mallard nested in grassland habitats of the west. In the present century, however, land use changes, including the deforestation of the eastern region, have caused a decline in the available breeding habitat of black ducks while simultaneously providing favorable habitat for nesting mallards. Johnsgard (1967) concluded that these environmental modifications were facilitating the colonization, by mallards, of extensive eastern areas formerly occupied by the black duck. The invasion of the mallard into black duck breeding territory has also resulted in the convergence of these two species on wintering grounds. Since the majority of pair bonding in both species occurs throughout the winter (Stotts and Davis 1960, Lebret 1961) and the courtship displays that lead to pair formation are similar (Johnsgard 1960), interspecific pairing can readily occur where these two species winter together. As a result of black duck hybridization with the much larger mallard gene pool and the constant reduction of its nesting habitat, it is believed by many that the black duck as a "pure" species will eventually disappear. The objectives of this study were to examine courtship activity and pair formation in 846 J. Wildl. Manage. 48(3):1984 This content downloaded from 157.55.39.110 on Sat, 24 Sep 2016 06:00:00 UTC All use subject to http://about.jstor.org/terms BLACK DUCK-MALLARD HYBRIDIZATION * Brodsky and Weatherhead 847 black ducks and mallards wintering together at the northern limit of their range and to determine the factors contributing to interspecific pairing between these two species. We thank H. G. Merriam for suggesting the suitability of the Manotick waterfowl population for this study, C. A. Barlow for comments on an earlier draft of this manuscript, and J. Sharkey-Thomas for feeding the ducks. Financial support was provided by the Nat. Sci. and Eng. Counc. of Can. and Carleton Univ.

70 citations



Journal ArticleDOI
TL;DR: Owing to its much smaller gene pool, the Black Duck is vulnerable to eventual swamping through hybridization and introgression, although the present hybridization rate is sufficiently low as to make this unlikely in the foreseeable future.
Abstract: ASTRACT: Changes in general fall and winter distributions of Mallards and Black Ducks over the past century have resulted in markedly increased sympatric contact during pair formation between these two forms, and have been responsible for increased opportunities for hybridization. Bureau of Sport Fisheries and Wildlife records of hybrids from 34 states indicate a minimal current hybridization rate that is about 4% of the frequency expected on the basis of mating according to mathematical probabilities of chance contact. Thus, hybridization is most frequent where both forms are almost equally abundant, indicating that no reinforcement of differences reducing hybridization in the primary zone of contact is detectable. The primary zone of sympatry has moved eastward approximately 300 miles during the past half century and will almost certainly continue to do so. Owing to its much smaller gene pool, the Black Duck is vulnerable to eventual swamping through hybridization and introgression, although the present hybridization rate is sufficiently low as to make this unlikely in the foreseeable future.

47 citations


Cites background or methods from "Wintering Distribution Changes in M..."

  • ...The extent of these changes in general distributions has been documented (Johnsgard, 1961b) through the use of the Audubon Society Christmas Counts, which have been conducted annually since 1900....

    [...]

  • ...…the relatively great wealth of data provided by these wing collections offer the first feasible means of an analysis of minimal hybrid incidence, because earlier sources of evidence regarding hybrid frequency were of unequal quality and available for only a few states (Johnsgard, 1961a)....

    [...]

  • ...51 52 THE AMERICAN MIDLAND NATURALIST 77(1) able regarding the situation in New Mexico, but determinations of the degree of sympatry and estimates of hybridization incidence for Mallards and Black Ducks have been made previously (Johnsgard, 1961a, 1961b)....

    [...]

  • ...It was earlier estimated that the gene pool of the Black Duck was approximately 17% that of the Mallard in the eastern United States (Atlantic and Mississippi flyways) during the 1950's (Johnsgard, 1961a)....

    [...]

  • ...This is perhaps an oversimplification of the actual situation (Johnsgard, 1961a), but the model allows for a ready calculation of expected heterozygote (hybrid) phenotypes for any combination of pure parental frequencies....

    [...]


01 Jan 1976

31 citations


Cites background from "Wintering Distribution Changes in M..."

  • ...Wing's (1943) summary ofthe first 40 years of Christmas Bird Count data indicated the values of utilizing this source of information long before major changes became apparent, and more recently Johnsgard (1961) summarized the data for the subsequent twodecade period of 1940-1949 and 1950-1959....

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Journal ArticleDOI
01 Jan 1961-The Auk
TL;DR: An attempt to understand the evolutionary relationships existing within a group of mallardlike ducks native to North America.
Abstract: 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, Anas platyrhynchos platyrhynchos L.; the Black Duck, Anas rubripes Brewster; the Florida Duck, Anas fulvigula fulvigula Ridgway; the Mottled Duck, Anas fulvigitla niiaculosa Sennett; the Mexican Duck, Anas diazi diazi Ridgway; and the New Mexican duck, Anas 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.

55 citations


"Wintering Distribution Changes in M..." refers background in this paper

  • ...The magnitude of this range extension has been great nevertheless, and the probable reasons for it have been discussed elsewhere (Johnsgard, 1959, 1961)....

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  • ...Arguments supporting the use of these data as unbiased estimates of wintering Mallard and Black Duck populations have been presented elsewhere (Johnsgard, 1959), and so will not be repeated here....

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Journal ArticleDOI
01 Jul 1943-The Auk

5 citations


"Wintering Distribution Changes in M..." refers background in this paper

  • ...Wing (1943) became interested in the ratios of Mallards to Black Ducks throughout he eastern states before the range shift was at all apparent, and calculated state ratios for the two forms on the basis of the data provided by the annual Audubon Society Christmas counts for the forty years 1900 to,…...

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Frequently Asked Questions (1)
Q1. What contributions have the authors mentioned in the paper "Wintering distribution changes in mallards and black ducks" ?

Since this trend is not likely to be reversed in the future, it will be of interest o follow it carefully and thus possibly to predict the fate of the Black Duck. Wing ( 1943 ) became interested in the ratios of Mallards to Black Ducks throughout he eastern states before the range shift was at all apparent, and calculated state ratios for the two forms on the basis of the data provided by the annual Audubon Society Christmas counts for the forty years 1900 to, 1939.