South African Shelduck Tadorna cana Scientific name definitions

David G. Allan
Version: 2.0 — Published February 23, 2023

Plumages, Molts, and Structure


South African Shelducks have 10 full-length primaries (numbered distally, from innermost p1 to outermost p10), about 18 secondaries (numbered proximally, from outermost s1 to innermost s15 and including 3 tertials, numbered distally t1 to t3), and typically 14 rectrices (numbered distally from innermost r1 to outermost r7 on each side of the tail. Little or no geographic variation in appearance has been reported (see Systematics). See Molts for terminology on molts and plumages.

Natal Down

Completely downy when hatched. Natal down is strikingly patterned, brown with white cheeks and underparts (contrasting sharply with brown crown) and distinct white patches on the sides of the back, sides of the rump, and wings. Male chicks are reported to have paler-colored breasts than females, but this difference may not be readily apparent in the field (1).

Juvenile (First Basic) Plumage

In Juvenile Plumage, both sexes resemble the adult male but are duller, with browner heads, auriculars, and necks, usually some white on the eyebrow, and extensive dusky brown on the white wing-coverts (2). That juveniles resemble males is unusual among sexually dimorphic birds, but accords with the partially reversed coloration and sexual roles in this species (3). In the Paradise Shelduck (Tadorna variegata) of New Zealand, adult females also have striking white heads and the juveniles resemble adult males as in the South African Shelduck (4) - none of the other Tadorna species show this pattern (5, 6). The sexes of juveniles can be differentiated as early as at 49 days (i.e., well before fledging) on the basis of the white rims around the eyes and bill of females; these regions are uniformly gray in juvenile males (7).

Formative Plumage

Similar to Definitive Basic Plumage in each sex except some scattered juvenile body feathers (especially among lower back, rump, and lower underparts) can be retained, brownish and more worn than replaced formative feathers. Juvenile remiges retained, the outer primaries browner, more pointed, and relatively worn compared to basic feathers. Some juvenile outer greater coverts are also often retained, narrow, rounded, brown, and contrasting with the squarer whiter formative coverts. Replaced formative coverts may also be washed brown, although this appears to be the case in some definitive basic feathers as well; study needed. Some outer rectrices may also occasionally be retained, narrow, brownish and notched. The head and breast of males can become bleached to buff and buffy whitish in worn plumage.

First and Definitive Alternate Plumages

Often referred to as "eclipse" plumages. Study is needed on the existence and extent of Prealternate Molts in this species (see Molts). Males may obtain paler and buffier heads post-breeding that may result from Prealternate Molts, or it could result from bleaching and wear; study needed. Otherwise, examination of Macaulay Library images indicates little or no molt or change in body-feather appearance during this period in either sex, except for the effects of wear.

Definitive Basic Plumage


Females are more striking in appearance than males due to their white head pattern, which is unusual among Anatidae. In Tadorna, only the Paradise Shelduck shows stronger reverse plumage dimorphism (5, 6). The hindcrown, neck, and lower throat are dark brown, contrasting with the white forehead, malar region, chin, upper throat, and through the eye, variably to include the upper sides of head to the entire sides of the head; lower auriculars can be brown, white, or white with brown feathers and often show a small rounded brown spot. The remainder of the body feathering is primarily russet. The tail, uppertail coverts, rump, and lower back are black, and this black feathering extends to the sides of the rump. The upperwing secondary coverts are primarily to entirely white and the primaries, upperwing primary coverts, and alula are black. Some proximal upperwing coverts can be washed pale brown, apparently plumage coloration and not staining. The secondaries are strongly tinged glossy green above, sometimes resulting in a green patch on the folded wing, and show white tips when fresh. The underwing secondary coverts and axillaries are white, and those of the greater primary coverts are basally white with increasingly broad black tips towards the outer wing.

It has been suggested that the white face patch in females increases in size with age (7), but this has been questioned based on data from captive birds (8). Four different head patterns have been identified (8). Usually, only the facial area is white, but in a small minority of individuals (ca. 0.35%) most, or even all (about 0.08%), of the head, upper neck, and throat are white. This categorization was subsequently expanded to recognize 12 different head patterns, with extensions to the white area falling into two main groups: either from behind the eye downwards, or downwards on the throat (9). In some cases, extensions in both directions are present, but females with small extensions to the white face patch predominate, whilst those with mainly white heads were scarce. There is no seasonal change in the facial pattern.

Definitive Basic Plumage in both sexes is distinguished from Formative Plumage by body feathering uniform in wear, without mixed generations; upperwing coverts uniform in wear, the feathers broad and white to predominantly white; primaries and secondaries longer, darker, glossier, and fresher; tail with uniformly broad and black rectrices.


The male is similar to the Definitive Basic female but the head and upper neck are uniformly plain gray and the nape and breast are paler tan creating a broad collar. An indistinct white partial eye ring can be present, and the lower porting of the gray can darken forming an indistinct gray ring around the lower neck. The head and breast can become bleached with wear, acquiring a bright creamy hue (10), but whether an alternate plumage following molt also exists requires further study (see Molts).

Aberrant Plumages

An instance of leucism or albinism has been recorded, with the bird described as "uniformly coloured pale creamy-white" (11).



Molt and plumage terminology follows Humphrey and Parkes (12) as modified by Howell et al. (13) and Pyle (14, 15). Under this nomenclature, terminology is based on evolution of molts along ancestral lineages of birds from ecdysis (molts) of reptiles, rather than on molts relative to breeding season, location, or time of the year, the latter generally referred to as “life-cycle” molt terminology (16; see also 17, 18). In north-temperate latitudes, the Humphrey-Parkes (H-P) and life-cycle nomenclatures correspond to some extent but terms are not synonyms due to the differing bases of definition. Prebasic molts often correspond to “post-breeding“ or “post-nuptial“ molts, preformative molts often correspond to “post-juvenile“ molts, and prealternate molts often correspond with “pre-breeding“ molts of life-cycle terminology. The terms prejuvenile molt and juvenile plumage are preserved under H-P terminology (considered synonyms of first prebasic molt and first basic plumage, respectively) and the former terms do correspond with those in life-cycle terminology. The molts and plumages of ducks have recently been revised based on the perceived evolution of molt strategies from geese, such that what is usually considered the pre-breeding molts in life-cycle terminology (molt of wings followed by a complete molt of body feathers following breeding), in summer and fall, is now considered the prebasic molts, and the post-breeding molts in life-cycle terminology (partial molts of some to most body feathers and some tertials and rectrices into "eclipse" plumage to provide crypsis for breeding in females and flightless period in both sexes), in spring and summer, is now considered the prealternate molts (14, 19, 15).

South African Shelduck exhibits either a Complex Basic or a Complex Alternate molting strategy (cf. 13, 20). It includes complete prebasic molts and a partial preformative molt, and may also include limited prealternate molts in both first and definitive cycles; study needed (see below).

Prejuvenile Molt

Occurs primarily August–September. Complete, at or near the natal site. Following hatching, the first contour feathers appear at ca. 18 days in the flanks and tail in captive chicks (7). At 28 days the chicks were still mainly downy, but feathers were present on the breast, flank, abdomen and scapulars, and the remiges were just emerging. By 35 days the upperwing coverts had appeared, the tail, breast, flanks and abdomen were well feathered, and the first feathers were appearing on the back, neck, crown and forehead, but the rest of the head was downy. At 42 days the breast, flanks, abdomen, and certain parts of the head and neck had mature feathers. At 49 days down-tipped feathers were present on the nape. At 56 days the chicks were almost completely feathered, including on the wings, but the nape feathers were still tipped with down, and the back and rump feathers were not fully developed. Growth was virtually complete by 63 days.

The sexes of captive chicks can be differentiated as early as 49 days (i.e., well before fledging) based on white rims around the eyes and bill of females; these regions are uniformly gray in young males, which in addition had paler-colored breasts (7).

Preformative Molt

Occurs primarily September-November. Birds undergoing the preformative molt largely avoid aggregations of birds undergoing definitive prebasic molt (9). Includes most body feathers, often 2–3 tertials, usually all rectrices, and some to most (perhaps occasionally all?) proximal upperwing secondary coverts, but no primaries, primary coverts, or secondaries other than the tertials. The larger scapulars, wing coverts, and rectrices are often molted last, as late as December on winter grounds. Some juvenile body feathers may be retained, especially in the lower back, rump, and lower underparts. Between 49 and 77 days of age, the white rims of females expanded, by ca. 90 days had merged to form the white face patch of the adult female, and continued to expand subsequently (7).

First and Definitive Prealternate Molts

These molts have not been confirmed but occur or have been reported in other species of Tadorna of seasonal climates (21, 4) and so might be expected in South African Shelduck, as reported (10). If present, occurs primarily in August–October and may include the head feathers but appears to include few other feathers based on examination of Macaulay images. Geldenhuys (10) also found that possibly two rectrix molts occur per cycle but confirmation is needed. The heads of males become paler during the post-breeding period, but study is needed on how much this is caused by molt vs. feather bleaching and wear (see images under Plumages).

Definitive Prebasic Molt

Occurs primarily in October-March, with flight feathers replaced prior to body feathers, as in other waterfowl (14). Throughout the range, the remiges are replaced during a relatively narrow midsummer window (late October to late February, mainly November‒January), when birds congregate at large, permanent freshwater bodies, apparently preferring sites undisturbed by man (22, 2, 23, 10, 9, 24). The largest recorded flocks occur at these molting localities, where concentrations of up to ca. 5,000 birds have been noted (25). This midsummer molting period is unusual. Other common southern African waterfowl, e.g., Spur-winged Goose (Plectropterus gambensis) , Egyptian Goose (Alopochen aegyptiaca) , Yellow-billed Duck (Anas undulata) and Anas erythrorhyncha, typically molt during midwinter (24). Midsummer molting corresponds with the peak rainfall season throughout most of the species’ distribution. At one major molting locality (Barberspan) the number of molting shelducks was positively correlated with rainfall. However, in the Western Cape Province winter-rainfall region, this species still molts in midsummer when rainfall is low. Molting during the dry season in the Western Cape may reflect the relatively recent colonization of this area, where the species has not yet had time to adjust its annual cycle to correspond with the local rainfall regime.

All of the remiges are shed within one to six days, starting with the primaries (2, 23). A few days later the primary and secondary coverts are molted. The flightless period spans ca. 28–40 days, including 3–6 days prior to the remiges being shed, and the flight feathers take approximately three days to harden. There is an apparent increase in body mass immediately prior to molt, unlike in several other southern African waterfowl (26), followed by a loss in weight of ca. 25%–35%, proportionately slightly greater in females than in males (mean 28% versus 26%), during the wing-molting period (2, 9). Body mass and pectoral muscle size decrease after the onset of molt, stabilize when the flight feathers are about two-thirds grown, and subsequently increase until molt is completed (27). This pattern is similar to that in Spur-winged Goose and Egyptian Goose, but differs from that of Yellow-billed Duck, Red-billed Duck, and Southern Pochard (Netta erythrophthalma). It appears likely that the reduced body mass recorded during the early molting period facilitates some flight on partially grown remiges later in the cycle, thereby permitting resumption of feeding as soon as possible.

Molting birds spend the day in deep water and only approach shallow water and shorelines at night to feed (2). It has been suggested that flightless birds apparently take little food (28) but this has been questioned (26). Flightless birds swim low in the water, are secretive, dive readily, and sometimes hide in emergent vegetation (23). Molt of rectrices is gradual and usually occurs about one month after wing molt is completed (2).

Bare Parts


Black in adults. The bills of hatchlings can be grayish washed pink, becoming grayish as juveniles.

Iris and Facial Skin

Iris is dark brown at all ages.

Tarsi and Toes

In adults, the tarsi are black. Females usually (80%) have dark gray feet blotched variably with light pink on the inner sides of the toes; the remainder have uniformly black feet as in males (9). The tarsi of hatchlings may be grayish washed pink, becoming grayish as juveniles.


Linear Measurements

Overall length 61‒64 cm (29). Males larger than females.

Linear measurements, in mm (30):

Adult males Adult females
Wing length 300–380 (mean 345, SD = 20.0, n = 23) 270–352 (mean 321, SD = 26.4, n = 10)
Tail length 101–151 (mean 126, SD = 16.1, n = 16) 95–144 (mean 123, SD = 14.6, n = 15)
Culmen 40.3–53.6 (mean 46.3, SD = 2.5, n = 56) 35.7–48.5 (mean 42.5, SD = 2.5, n = 44)
Tarsus length 55.1–72.1 (mean 65.7, SD = 3.0, n = 47) 52.6–68.0 (mean 59.8, SD = 3.4, n = 34)


Males are heavier than females. Males: 900–2,150 g (mean 1,452 g, SD = 208.9 g, n = 277 confirmed adult males only with 90% of records from Nov.–Dec. when captured at molting localities mainly in the Free State and North-West provinces) (30), 910–2,200 g (mean 1,357 g, n = 1,171; 31), 1,032–2,032 g (mean 1,527 g, n = 171) (Barberspan; 32), mean 1,758 g (n = 152) (Barberspan; 2), 1,012–1,295 g (mean 1,187 g, n = 5) (Free State Province; 33). Females: 800–1,665 g (mean 1,197 g, SD = 187.4 g, n = 235 confirmed adult females only with 87% of records from Nov.–Dec. when captured at molting localities mainly in the Free State and North-West provinces) (30), 700–1,835 g (mean 1,115 g, n = 1,092) (31), 872–1,835 g (mean 1,229 g, n = 215) (Barberspan; 32), mean 1,417 g (n = 222) (Barberspan; 2), 1,049–1,240 g (mean 1,173 g, n = 3) (Free State; 33). The radical variation in both males and females is largely due to extensive weight loss during the wing-molting period (9).

Recommended Citation

Allan, D. G. (2023). South African Shelduck (Tadorna cana), version 2.0. In Birds of the World (G. D. Engelbrecht, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.soashe1.02