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Description and Identification of American
Black Duck, Mallard, and Hybrid Wing Plumage

Results


Historical and Current Descriptions of Mallard and Black Duck Wing Plumages

Mallard

First scientific descriptions of the Mallard (Latham 1785; Pennant 1785) differed little from earlier nonscientific descriptions or subsequent scientific accounts. Palmer (1976:276-280) described Mallard wing plumage as follows:
  1. the greater secondary coverts are white subterminally and black at the tips in both sexes in all plumages, with the white of the female often extending proximally beyond the metallic area (speculum) but not onto innermost secondaries;
  2. the secondaries forming the speculum are black subterminally with broad white tips in all plumages, forming a trailing white bar in both sexes; and
  3. axillars and most of the wing lining are white in both sexes, but the most proximal of the light underwing coverts have dark barring in the female.

Black Duck

Earliest written descriptions of the Black Duck appeared only after initial European exploration of North America's eastern shore. The modern definition is as follows (Palmer 1976:321-326):
  1. greater secondary coverts terminal black, with sometimes "more or less of a thin or poorly defined white line forward of this black stripe";
  2. secondaries have broad black ends, which vary from bird to bird from white at the very tip to ends solid black; and
  3. in the wing lining, many greater coverts are light gray, others white, but some sooty-fuscous coverts with whitish margins generally are present beyond the bend of the wing, and axillars are white.

Palmer emphasized that "typical" Black Duck and Mallard wings also differed in other respects including overall color, amount of light edging on feathers, extent of iridescence (but not necessarily or consistently the color) of the speculum, presence of vermiculation, and presence of internal markings in feathers. Although further variation is introduced by the presence in wing collections of domestic Mallards, which display a range of characters unlike those of the wild Mallard (Delacour 1964:154-166), the modern consensus remains that "typical" wings (as described by Palmer for each species) are strikingly different to even the casual observer.

Older accounts of Black Duck wing plumage (from 1785; references in Appendix) differ from Palmer's (1976) description. In these older accounts, the occasional presence of white subterminally on the greater secondary coverts was never mentioned as a species character except by Phillips (1912), who mentioned that some Black Ducks in New England showed this trait. Palmer's description agrees with commonly accepted criteria used by those who currently handle Black Ducks in banding operations: the Black Duck may or may not have "some" white anterior to the speculum. For example, the description in Carney's (1992:141) key ("[secondaries] blue bordered front or back (not both) with white") for Black Duck and Mottled Duck allows less expression of white than Palmer (1976). Although Palmer's description may accurately describe wings of mid- to late 20th-century birds assumed to be Black Ducks, historical evidence from the references in the Appendix supports our contention that subterminal white on the secondary coverts of Black Ducks is rare, and at its most extreme, it is a pale gray subterminal tinge in some birds as described by Cramp and Simmons (1977).

Accounts did not mention white as occurring on the terminal edge of the secondary feathers of Black Ducks until Nuttall (1834). Thereafter, some authors listed this character while others did not, and some attributed it to males only. Not until the 20th century did most authors list white as possibly being present as a thin terminal line, and the sex specificity was retained for at least 25 more years (e.g., Forbush 1925). Forbush (1925) and Bagg and Eliot (1937) attributed this character to adults only, but age and sex specificities of this trait were omitted by all authors after 1940. It may be that terminal white on the secondaries was always variable and sometimes inconspicuous, giving the impression that "most" Black Ducks were without white, or concomitantly, that the proportion of birds with white-tipped secondaries increased in this century. Regardless, the important determination for plumage analysis is that historical descriptions support the conclusion that Black Ducks from across their range may have a more-or-less complete terminal band of white on the secondaries that form the speculum, and the maximum width may be equivalent to that on Mallards.

Underwing Plumage

Descriptions of underwing plumage in both the Black Duck and the Mallard have historically varied. "White" or "silvery white" are always listed as the most conspicuous features of this plumage in the Black Duck. Certainly, from a distance as a field mark, this trait is distinguishing. However, paintings by several artists showed dark feathers in the underwing of the Black Duck [Audubon 1838, Fuertes (in Forbush 1925 and Oberholser 1974), Hunt (in Heilner 1946), Ruthven and Zimmerman (1965), Weber (in Wetmore 1965), Ogilvie (1975), and Hines (1978)]. Similarly, a photograph in Wright (1954) shows some dark feathers, and Palmer (1976) specifically mentioned "sooty-fuscous" feathers on the underwing.

The Mallard has been described as generally having "creamy white" underwings. We observed that male Mallards trapped in Québec (1975-90) and male specimens in Canadian museums collected before 1935 did not have dark underwing feathers. Mallard females had a variable but always small number (generally less than seven) of dark underwing feathers. In obvious contrast, Black Ducks of both sexes had a variable, but consistently large, number (always more than 10) of these dark feathers. A large group of birds, believed to be hybrids, fell between Mallards and Black Ducks for this character. Ball's (1934:23) comment that a hybrid specimen showed its A. rubripes inheritance in the underwing coverts through a broken row of dark spots near the edge of the wing is the only reported prior observation of this phenomenon.

Species Descriptions and the Characters of Study Skins and Wings

Mallard Wings in Museums and Modern Parts Collections

We examined 469 specimens collected from 1867 to 1977 in areas outside North America. These birds were presumed to have had no probability of contact with Black Ducks.

Palearctic and Orient.  All but one of 332 Mallard skins (adult male from Sweden, 1908) were typical, as there were no obvious aberrancies in body plumage, white edging on the anterior and posterior borders of the speculum was complete (>80% of all feathers of the speculum), there were no large dark underwing feathers, and there were fewer than 10 small dark underwing feathers. The single aberrant bird appeared to be a cross with a domestic variety.

Great Britain.  All but 3 of 137 wings analyzed from the British Parts Collection Surveys showed typical Mallard features as above. One exception had narrow white bars, others had 3 and 9 small dark feathers in the underwing.

North America.  We examined 1,705 wings from the U.S. Parts Collection Survey for the Pacific Flyway (1976-77 season), 2,280 wings from the Canadian Parts Collection Survey (British Columbia, 1975-76 and 1976-78 hunting seasons), and 85 older skins (1840-1937) from the collection of the Academy of Natural Sciences, Philadelphia, Pennsylvania, to evaluate the modern description of Mallards. These specimens were selected because of their low probability of contact with Black Ducks, Mexican Ducks, or Mallard × Mexican Duck hybrids (i.e., wings from northern California, Nevada, Oregon, Washington, Idaho, western Montana, western Colorado, and western Wyoming). All wings in the Pacific Flyway sample had white wing bars above and below 80% or more of the speculum and were otherwise typical Mallards. Two females had one brown feather on an underwing; one female had three brown feathers on one underwing. Only one of the wings from British Columbia (male) had characters different from those of a typical Mallard (dark feathers in the underwing). In the Philadelphia collection, 52 male skins were typical Mallards in all respects; one male skin (6 August 1927, Bear River, Utah) was typical on the dorsal wing surface and elsewhere but had two dark brown feathers on the underwing; 32 female skins were typical in all respects except that four skins each had one dark brown feather in the underwing.

Black Duck Wings in Museums and Modern Parts Collections

We examined 312 Black Duck skins at the Academy of Natural Sciences, Philadelphia, Pennsylvania; American Museum of Natural History, New York, New York; and Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, each of which contained substantial collections of comparatively old specimens (1873-1939). Ninety-seven percent of the males and 99 percent of the females resembled in general form and coloration typical Black Ducks per Cramp and Simmons (1977). These specimens had either no white on the dorsal surface of the wing or only a lower bar (white terminal) on the secondaries. Only two of these ducks had fewer than 10 brown feathers on the underwing.

A Revised Description of Mallard Wing Plumage

Based upon our historical literature review and empirical assessment of study skins, wings, and live birds, we contend that typical Mallard wing plumage can be characterized as follows (Figs. 1 and 2):

Figure 1   Figure 2
Fig. 1.  Photograph of a typical wing from an immature male Mallard illustrating the range of dorsal and ventral characters expected in wild forms. Note the sharp borders between white and black bordering the speculum, the large and even width of this white from the proximal to the distal end of the speculum (considered 100% for comparison), and the overall uniform white of the underwings. This wing has slightly more white than average on the proximal edge of the speculum.   Fig. 2.  Dorsal and ventral photographs of a typical wing from an immature female Mallard illustrating the same features as in Figure 1. Note the further extent of white across the tertials in the female than in the male.

 
Dorsal: The speculum is bounded by anterior and posterior white bars, each 
      usually more than 5 mm wide, but not always so. These bars are continuous 
      and delimit without interruption more than 80% of the iridescent 
      secondaries. This white has strictly delimited margins with adjacent 
      colors including black on the posterior bar; fuscous-gray, gray, or shades
      of brown, depending upon age, sex, and season, and black on the anterior 
      subterminal bar (color terminology of Palmer 1976). The remainder of the 
      wing dorsum for both sexes and all ages is as described by Palmer (1976) 
      and Cramp and Simmons (1977). 

Ventral: Underwing coverts (lining of the wing) are white in both sexes. 
      Male Mallards never have dark feathers in the underwing coverts; but female 
      Mallards are more variable and may have a few (usually less than seven but 
      always less than 10) dark brown feathers on the anterior edge of the 
      underwing.

A Revised Description of Black Duck Wing Plumage

Based upon our literature review and assessment of study skins, wings, and live birds, we contend that Black Duck wing plumage is characterized as follows (Fig. 3):

  Figure 3  
  Fig. 3.  Dorsal and ventral photographs of a typical wing from a Black Duck (in this case, an adult male) illustrating characters expected in wild forms. Note lack of an anterior white bar bordering the speculum, the trace of white on the posterior bar, and the presence of more than 10 brown feathers on the underwing.  

Dorsal: Black Ducks can have white posterior to the speculum, but they never 
      have white anterior to the speculum. White posterior to the speculum may 
      vary from none, to a thin white edge, to that present on typical Mallards. 
      The lack of white anterior to the speculum on the greater secondary 
      coverts strictly separates Black Ducks from Mallards. However, Black 
      Ducks often do have a pale gray subterminal line (terminology of Cramp 
      and Simmons 1977) on these coverts, and on some birds this gray line is 
      suffused with one of several shades of "brown" or "tan." The overall 
      effect is difficult to describe precisely, since several colors (#23 [Raw
      Umber], #24 [Buff], #36 [Amber], #37 [Antique Brown], #38 [Tawny], #39 
      [Cinnamon], #40 [Cinnamon Rufous], and various combinations with one of 
      the Neutral Grays [terminology of Smithe 1974a, 1974b]) may be present. 
      The result is a line of variable width adjacent to the terminal black 
      that is distinctly not white in comparison with the white on the dorsal 
      surface of a Mallard wing. 

Ventral: All Black Ducks have more than 10 dark brown feathers on or near the
      leading edge in the lining of the wing (Fig. 3).

Independent Confirmation of the Revised Black Duck Wing Description

We applied our diagnostic criteria to an independent sample of older Black Duck skins collected from 1842 to 1939 that are deposited in the Smithsonian Museum of Natural History. At arm's length, we viewed each available skin in the entire collection labeled as either a "Mallard," "Black Duck," "domestic Mallard," "aberrant form," "Mallard-like," or "hybrid." We used the presence of white and more than 10 dark feathers to classify each skin as (a) Black Duck-like, (b) Mallard-like, or (c) an obvious mixture of the two or a domestic breed. (These initial decisions were made without knowledge of the information on labels attached to the skins.) We then evaluated those specimens in category "a" with the Black Duck wing criteria. Ninety of 94 specimens (96%) met the dorsal and ventral wing criteria. No birds we classified as "b" or "c" were labeled Black Ducks by the original collectors or determined to be Black Ducks by us after closer inspection. We concluded from this sample that in excess of 95% of all Black Ducks meet the proposed criteria.

Black Duck × Mallard Hybrid Wing Plumage

Available descriptions of Black Duck × Mallard hybrids by Dutcher (1889), Eaton (1903), Bigelow (1907), Kortright (1942), and Gillham and Gillham (1996) are of limited value because the authors could not be certain of their specimens' genetic history. Only Phillips (1915, 1921) described ducks he knew were progeny of mixed pairs. He found F1 hybrids to be darker overall than Mallards, but all had both upper and lower white wing bars bordering the speculum. He found reduced amounts of white in F2 progeny and young from backcrosses to Black Ducks. Upper wing bars were absent in only one F2 bird. He did not comment on the appearance of the underwing of his hybrids.

We were able to locate eight of Phillips' Black Duck × Mallard specimens from his hybridization studies in the Museum of Comparative Zoology, Harvard University. Seven of these birds did not fit the criteria for typical Black Ducks or Mallards, and one bird, F2 male number 172, was indistinguishable from a typical Black Duck as noted by Phillips (1915:78). No other historical specimens of progeny from confirmed hybrid matings were known to us.

Hybrids Propagated at Jamestown

None of the 23 female and 42 male F1 hybrids propagated at the Jamestown facility matched the above criteria for typical Black Duck or Mallard wing plumage. These birds all had narrower, and usually less distinct, white wing bars than Mallards and too few (to be a Black Duck) or too many (to be a Mallard) dark feathers on the underwing. Twenty-two male F2, six of 13 female F2, five male F3, and two of nine female F3, did not meet criteria for typical Black Duck or Mallard wing plumage based on presence/absence of white wing bars and underwing dark feathers. In backcrosses of F1 hybrid ducks to Black Ducks, 47 of 49 males and 35 of 44 females did not fit the standard criteria for the two species. In backcrosses of F1 hybrids to Mallards, 40 of 49 males and four of 42 females did not fit the species criteria.

In sum, all F1 hybrids, regardless of sex, could be distinguished from parental species by using the species definitions for white on the dorsal surface of the wing and dark feathers on the underwing. All male F2 and F3 generations showed these characters, but only 36% of the female F2 and F3 showed them. Our wing characters correctly identified 96% of males and 80% of females resulting from backcrosses between F1 hybrids and Black Ducks, but we could identify only 82% of males and 10% of females resulting from backcross of F1 hybrids to Mallards.

Figures 4 through 7 provide examples of hybrids from the propagated flock, wing receipts in Canadian and U.S. Parts Collection Surveys, and birds handled in Québec and New Jersey banding operations during 1976-80. Figure captions note those characters that identify the bird as of hybrid origin.

Figure 4   Figure 5
Fig. 4.  Dorsal and ventral photographs of a wing from an adult male hybrid resembling for the most part a Black Duck. Note the trace of an anterior bar (hybrid character), restricted posterior bar on the secondaries about 10% the width of a normal male Mallard posterior bar (a Black Duck character), and the presence of more than 10 brown feathers on the underwing (Black Duck character).   Fig. 5.  Dorsal and ventral photographs of a wing from an immature female hybrid resembling for the most part a Black Duck. Note the anterior bar about 50% the width of that of a Mallard (hybrid character, the posterior bar about 10% of that of a Mallard (Black Duck character), and more than 10 brown feathers on the underwing (Black Duck character).
Figure 6   Figure 7
Fig. 6.  Dorsal and ventral photographs of a wing from an adult female hybrid resembling for the most part a Mallard. Note the anterior and posterior bars about 50% that of a Mallard (hybrid character, and more than 10 brown feathers on the underwing (Black Duck character). Many of the brown feathers are small and do not show well in the photograph except near the bend of the wing (wrist.   Fig. 7.  Dorsal and ventral photographs of a wing from an immature female hybrid resembling for the most part a wing intermediate between Black Duck and Mallard. Note that the anterior bar is almost that normally found on Mallards (Mallard character), but the posterior bar is only about 50% of that found on Mallards. The underwing has six brown feathers. The unlikeness of the two wing bars identifies this wing as a hybrid even though it was only slightly darker than an average mallard wing. Many would identify this wing as a mallard.

Sex Determination of Hybrid Wings

Undamaged wings of 131 hand-reared hybrids were measured for comparison with Carney's (1964, 1992) keys for Black Ducks. Three of 52 (6%) adult male wings measured less than 282 mm, Carney's lower limit criterion for absolute identification to sex based on this measurement. All of the smaller wings were in the in-between grouping (279-281 mm), which requires inspection of plumage characters for sex determination in Carney's key. Eight of 59 (14%) wings from adult females exceeded 278 mm, Carney's upper limit criterion for absolute identification of females on the basis of wing length. Of those eight, four fell within the range 279-281 mm, which would have required further inspection of the plumage. The four remaining wings would have been initially identified as from males, on the basis of length, for an error rate of 7%. Three of the wings in question, however, more closely resembled wings from Mallards than Black Ducks and were correctly identified by presence of plumage characters used to identify sex of Mallards (Carney 1992). The remaining wing would be misidentified with any but most careful inspection in addition to measurement. We conclude that sex of an adult hybrid wing is misclassified 2-7% of the time using wing characters, and that this error is biased against correct identification of females.

The measurements for the immature birds identified all but one of 10 females correctly with current Canadian Wildlife Service criteria for wing length of < 271 mm (Reed and Boyd 1972). Wing chords of 10 immature males exceeded 272 mm, Reed and Boyd's lower limit criterion for identification of young males. Bias, again, is against correct identification of females. The single wing from a female that was misidentified resembled the wing of a Black Duck. Only careful inspection would have revealed its sex after the measurement was made.

Because the error rate for determining sex of hybrid wings seems to be approximately in the range < 5%, we conclude that current techniques for determining the sex of Black Ducks are sufficient to determine the sex of hybrids from wings alone. Measurements usually suffice, but a careful worker will take advantage of both measurements and plumage characters to determine sex, especially if the wing has any white anterior to the speculum. In such instances, criteria for determining sex of Mallard wings easily apply (Carney and Geis 1960, Carney 1992).


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