Breeding

The South African Shelduck breeds in isolated pairs, usually well separated from other pairs, probably at least partly due to their specialized nesting requirements.

Breeding has been recorded from as far north as ca. 20˚S in Namibia and as far east as 30˚E in KwaZulu-Natal (115 Cumming, G. S., D. M. Harebottle, J. Mundava, N. Otieno, and S. J. Tyler (2016). Timing and location of reproduction in African waterfowl: an overview of >100 years of nest records. Ecology and Evolution 6:631–646. Close ), although breeding even further east, at ca. 29˚50’S, 30˚32’E, near Durban, has been noted (DGA personal observation).

The breeding period is highly circumscribed, unlike in the Egyptian Goose (Alopochen aegyptiaca). A comprehensive analysis of seasonality from throughout the range, comprising 681 georeferenced records, shows that hatching dates are highly synchronous with a marked September peak, and the vast majority of records are in July‒November (although hatching dates apparently cover all months) (115 Cumming, G. S., D. M. Harebottle, J. Mundava, N. Otieno, and S. J. Tyler (2016). Timing and location of reproduction in African waterfowl: an overview of >100 years of nest records. Ecology and Evolution 6:631–646. Close ). Nesting is consistently in the drier months, i.e., when rainfall is below the annual average. Breeding seasonality in southern Africa is similar to that exhibited by the Egyptian Goose and African Black Duck (Anas sparsa), and is unusual compared to most other southern African waterfowl that breed during the summer, i.e., the period of highest rainfall throughout most of the region (115 Cumming, G. S., D. M. Harebottle, J. Mundava, N. Otieno, and S. J. Tyler (2016). Timing and location of reproduction in African waterfowl: an overview of >100 years of nest records. Ecology and Evolution 6:631–646. Close , 24 Ndlovu, M., P. A. R. Hockey, and G. S. Cumming (2017). Geographic variation in factors that influence timing of moult and breeding in waterfowl. Zoology 122:100–106. Close ). Egg-laying (as opposed to hatching) data from across the range confirm early winter to early summer breeding (29 Allan, D. G. (2005). South African Shelduck Tadorna cana. In Roberts Birds of Southern Africa. Seventh Edition. (P. A. R. Hockey, W. R. J. Dean, and P. G. Ryan, Editors), The Trustees of the John Voelcker Bird Book Fund, Cape Town. pp. 93–95. Close ).

In Eastern Cape Province, courtship begins in February and continues until May, by June most pairs are firmly established, egg-laying occurs July–October, newly hatched young are observed August–November (mainly September–October), and full-grown young are seen with their parents from October until December (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close , 116 Taylor, J. S., and J. Vincent (1949). Breeding dates of game birds. Ostrich 20:38–39. Close ). In Free State Province, egg-laying occurs during a relatively short period that is consistent between years, even when rainfall varies widely (103 Geldenhuys, J. N. (1980). Breeding seasons of Egyptian Geese and South African Shelducks in Central South Africa. In Proceedings IV Pan-African Ornithological Congress (D. N. Johnson, Editor), Southern African Ornithological Society. pp. 267–275. Close ). The earliest laying date was about 17 May and the latest about 25 September, i.e., spanning 18 weeks, peaking during the last week of July. A comparison of breeding seasonality between Northern, Eastern, and Western Cape provinces found little difference between these regions, with peak activity (largely based on observations of chicks) reported July–October in all three areas (117 Little, R. M., K. C. Vester, and T. M. Crowe (1995). Temporal and spatial patterns of breeding activity of 12 duck species (Anatidae) in the Cape Provinces, South Africa, and their implications for hunting seasons. South African Journal of Wildlife Research 25:17–22. Close ). Atlas data (again based largely on sightings of young) from throughout the species’ range show main breeding during July–November (peak August–October), but with a clear indication of earliest breeding, by about two months, in the north of the range (peak August) compared to the south (peak October) (43 Harrison, J. A., D. G. Allan, L. G. Underhill, M. Herremans, and A. J. Tree, Editors (1997). The Atlas of Southern African Birds. Volume 1. Non-passerines. BirdLife South Africa, Johannesburg, South Africa. Close ).

Nesting occurs during the dry (midwinter) period, explaining why breeding is largely restricted to permanent, and not seasonal, wetlands (103 Geldenhuys, J. N. (1980). Breeding seasons of Egyptian Geese and South African Shelducks in Central South Africa. In Proceedings IV Pan-African Ornithological Congress (D. N. Johnson, Editor), Southern African Ornithological Society. pp. 267–275. Close ). Chicks feed largely on submerged aquatic plants in shallow water and such conditions are optimal during the dry winter period, explaining the timing of breeding. Nesting during the dry season may also be related to the species’ subterranean nests, which may be prone to flooding (118 Skead, D. M., and W. R. J. Dean (1977). Seasonal abundance of Anatidae at Barberspan. Ostrich 12(Supplement):49–64. Close , 24 Ndlovu, M., P. A. R. Hockey, and G. S. Cumming (2017). Geographic variation in factors that influence timing of moult and breeding in waterfowl. Zoology 122:100–106. Close ). In addition, there is scant littoral vegetation at this time of year, aiding in predator detection. Breeding in the winter-rainfall Western Cape Province may be later than in other parts of the range, although still overlapping the wet period and apparently as part of a broader latitudinal trend, rather than a specific dichotomy between the summer- and winter-rainfall regions. Breeding during the wet season in Western Cape may reflect the relatively recent colonization of this area and that the species has not yet adjusted its breeding (and molt) to correspond with the rainfall regime (24 Ndlovu, M., P. A. R. Hockey, and G. S. Cumming (2017). Geographic variation in factors that influence timing of moult and breeding in waterfowl. Zoology 122:100–106. Close ).

Selection Process

Females lead the pair in prospecting for nest sites, and males are largely responsible for defending the area from other pairs (1 Geldenhuys, J. N. (1980). Breeding ecology of the South African shelduck in the southern Orange Free State. South African Journal of Wildlife Research 10:94–111. Close ).

Microhabitat

Nests are located in holes in the ground, especially those of aardvark (Orycteropus afer) (1 Geldenhuys, J. N. (1980). Breeding ecology of the South African shelduck in the southern Orange Free State. South African Journal of Wildlife Research 10:94–111. Close , 119 Tarboton, W. (2011). Roberts Nests and Eggs of Southern African Birds. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa. Close ). Of 14 nests, 11 were in aardvark burrows and three were in smaller excavations, either of springhares (Pedetes capensis) or porcupines (Hystrix africaeaustralis) (1 Geldenhuys, J. N. (1980). Breeding ecology of the South African shelduck in the southern Orange Free State. South African Journal of Wildlife Research 10:94–111. Close ). Another nest was situated ca. 9 m down an aardvark burrow (120 Edelsten, G. (1932). Notes on the nest of the South African Shelduck. Ostrich 3:61. Close ). The species also apparently nests occasionally among rocks (66 Horsbrugh, B. (1912). The Game-birds and Water-fowl of South Africa. Witherby and Co., London, UK. Close ), once in haystack (119 Tarboton, W. (2011). Roberts Nests and Eggs of Southern African Birds. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa. Close ), and sometimes in anthropogenic ducts and culverts (3 Maclean, G. L., and G. Darroll (1986). Ducks of Sub-Saharan Africa. Acorn Books, Johannesburg, South Africa. Close ).

This unusual choice of typical nest site is probably related to the nature of the xeric vegetation at and around the wetlands this species inhabits, i.e., the absence of secure breeding sites in the form of dense wetland vegetation or tall trees (91 Geldenhuys, J. N. (1976). Physiognomic characteristics of wetland vegetation in South African Shelduck habitat. South African Journal of Wildlife Research 6:75–78. Close ). Underground nesting has also been related to an intolerance of high temperatures in the species (44 Geldenhuys, J. N. (1981). Effect of temperature and rainfall on the distribution of the South African Shelduck Tadorna cana. South African Journal of Zoology 16:167–171. Close ) but this requires confirmation (115 Cumming, G. S., D. M. Harebottle, J. Mundava, N. Otieno, and S. J. Tyler (2016). Timing and location of reproduction in African waterfowl: an overview of >100 years of nest records. Ecology and Evolution 6:631–646. Close ). Heavy rainfall may flood and collapse breeding burrows, resulting in the birds being precluded from nesting and prematurely concentrating at the large waterbodies usually only frequented during the post-breeding period (118 Skead, D. M., and W. R. J. Dean (1977). Seasonal abundance of Anatidae at Barberspan. Ostrich 12(Supplement):49–64. Close , 24 Ndlovu, M., P. A. R. Hockey, and G. S. Cumming (2017). Geographic variation in factors that influence timing of moult and breeding in waterfowl. Zoology 122:100–106. Close ). The choice of nest site may therefore be implicated in the species’ largely xeric distribution. It is unclear if the choice of nest site is more or less hazardous (to the incubating female and the eggs) than more typical waterfowl nesting situations (109 Siegfried, W. R. (1976). Sex ratio in the Cape Shelduck. Ostrich 47:113–116. Close ).

Site Characteristics

Nests are sited up to 2.0 km from the territorial waters (1 Geldenhuys, J. N. (1980). Breeding ecology of the South African shelduck in the southern Orange Free State. South African Journal of Wildlife Research 10:94–111. Close , 119 Tarboton, W. (2011). Roberts Nests and Eggs of Southern African Birds. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa. Close ).

Structure and Composition

Eggs are laid in a bowl of grass and down feathers constructed by the female (119 Tarboton, W. (2011). Roberts Nests and Eggs of Southern African Birds. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa. Close ). In three nests under captive conditions, both contour (9–71 feathers) and down (61–940 feathers) feathers were used (121 Siegfried, W. R. (1964). The number of feathers in the nests of South African Anatidae. Ostrich 35(1):61. Close ). One nest under natural conditions apparently included a large dry thistle weed (120 Edelsten, G. (1932). Notes on the nest of the South African Shelduck. Ostrich 3:61. Close ).

Maintenance or Reuse of Nests

Sites are regularly re-used in subsequent years (120 Edelsten, G. (1932). Notes on the nest of the South African Shelduck. Ostrich 3:61. Close , 119 Tarboton, W. (2011). Roberts Nests and Eggs of Southern African Birds. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa. Close ).

Shape

Elliptical (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close , 31 Maclean, G. L. (1993). Roberts’ Birds of Southern Africa. Sixth edition. John Voelcker Bird Book Fund and New Holland, Cape Town, South Africa. Close ).

Size

64.5–72.0 × 48–52 mm (mean 68.7 × 50.3 mm, n = 13) (122 James, H. W. (1970). Catalogue of Birds’ Eggs in the Collection of the National Museums of Rhodesia. Trustees of the National Museums of Rhodesia, Salisbury, Zimbabwe. Close , Ditsong Museum of Natural History collection).

Mass

74.5–99.5 g (mean 89.0 g, n = 50) (31 Maclean, G. L. (1993). Roberts’ Birds of Southern Africa. Sixth edition. John Voelcker Bird Book Fund and New Holland, Cape Town, South Africa. Close ).

Color and Surface Texture

Unmarked pure white or cream-colored with a matt surface (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close , 31 Maclean, G. L. (1993). Roberts’ Birds of Southern Africa. Sixth edition. John Voelcker Bird Book Fund and New Holland, Cape Town, South Africa. Close ).

Clutch Size

All apparently confirmed complete clutches (n = 26) comprised 4–11 eggs (120 Edelsten, G. (1932). Notes on the nest of the South African Shelduck. Ostrich 3:61. Close , 123 Heÿl, C. W. (1994). Clutch sizes of ducks in the south-western Cape. South African Journal of Wildlife Research 24:6–11. Close , 124 Lepage, D. (1999). A summary of nest records of southern African birds. Unpublished manuscript. Percy Fitzpatrick Institute, University of Cape Town, Cape Town, South Africa. Close , 125 Brown, C. J., P. A. Bridgeford, S. G. Braine, M. Paxton, and W. Versfeld (2015). Breeding data on the birds of Namibia: laying months, colony and clutch sizes and egg measurements. Ornithological Observations 6:92–196. Close , Ditsong Museum of Natural History collection), except for one record of 15 eggs (35 Delacour, J. (1954). Waterfowl of the World. Volume 1. Country Life Books, London, UK. Close ). There are three apparently confirmed records of complete four-egg clutches. The mean and modal clutch sizes are 7.4 and 7.0 eggs, respectively.

Egg Laying

The egg-laying period is highly circumscribed (115 Cumming, G. S., D. M. Harebottle, J. Mundava, N. Otieno, and S. J. Tyler (2016). Timing and location of reproduction in African waterfowl: an overview of >100 years of nest records. Ecology and Evolution 6:631–646. Close ). Egg-laying data from across the range confirm early winter to early summer breeding, with a marked peak in late winter, in July–August (68%), the vast majority in June–September (86%), and all records are during March–December (n = 115) (29 Allan, D. G. (2005). South African Shelduck Tadorna cana. In Roberts Birds of Southern Africa. Seventh Edition. (P. A. R. Hockey, W. R. J. Dean, and P. G. Ryan, Editors), The Trustees of the John Voelcker Bird Book Fund, Cape Town. pp. 93–95. Close ).

In Free State Province, the earliest laying date was about 17 May and the latest about 25 September, i.e., spanning 18 weeks, peaking during the last week of July, and 90% of clutches were started during the seven-week period 20 June–17 August (n = 171) (103 Geldenhuys, J. N. (1980). Breeding seasons of Egyptian Geese and South African Shelducks in Central South Africa. In Proceedings IV Pan-African Ornithological Congress (D. N. Johnson, Editor), Southern African Ornithological Society. pp. 267–275. Close ). Other precise egg-laying dates for specific regions include:

• Namibia: April (n = 1), May (n = 2), June (n = 5), July (n = 3), August (n = 2), September (n = 1) (125 Brown, C. J., P. A. Bridgeford, S. G. Braine, M. Paxton, and W. Versfeld (2015). Breeding data on the birds of Namibia: laying months, colony and clutch sizes and egg measurements. Ornithological Observations 6:92–196. Close ).
• Botswana: May (n = 1), June (n = 3), July (n = 5), August (n = 2), September (n = 1), September/October (n = 1), November (n = 1), December/January (n = 1) (49 Tyler, S. J. (2020). Changing status of South African Shelduck (Cape Shelduck) Tadorna cana in Botswana. Babbler 66:4–10. Close ).
• South Africa: Former Transvaal Province (northeastern South Africa): April (n = 1), May (n = 1), June (n = 1), July (n = 3), August (n = 8) (126 Tarboton, W. R., M. I. Kemp, and A. C. Kemp (1987). Birds of the Transvaal. Transvaal Museum, Pretoria, South Africa. Close ).
• South Africa: Western Cape Province: August (n = 1), September (n = 4) and October (n = 1) (45 Winterbottom, J. M. (1968). A Check List of the Land and Fresh Water Birds of the Western Cape Province. Annals of the South African Museum 53:1–276. Close ).

This regional egg-laying information tends to confirm earlier laying in the north, although sample sizes are small and coverage uneven.

Period

The incubation period and the interval between the laying of eggs is unknown, but has been assumed to be about 30 days and one day, respectively (103 Geldenhuys, J. N. (1980). Breeding seasons of Egyptian Geese and South African Shelducks in Central South Africa. In Proceedings IV Pan-African Ornithological Congress (D. N. Johnson, Editor), Southern African Ornithological Society. pp. 267–275. Close ). Incubation probably only commences when the clutch is complete or close to completion, such that the young hatch fairly close together and can be taken simultaneously to water.

Parental Behavior

Incubation is solely by the female (109 Siegfried, W. R. (1976). Sex ratio in the Cape Shelduck. Ostrich 47:113–116. Close ). Males seem to spend most of the incubation period close to the nesting burrow and away from the aquatic breeding territory, and apparently warn the female of potential predators by loud hissing (1 Geldenhuys, J. N. (1980). Breeding ecology of the South African shelduck in the southern Orange Free State. South African Journal of Wildlife Research 10:94–111. Close , 127 Skinner, N. J. (1997). The breeding seasons of birds in Botswana 3: non-passerine families (Ostrich to Skimmer). Babbler 32:10–23. Close ). The female leaves the nest once or twice a day, joining the male to feed (119 Tarboton, W. (2011). Roberts Nests and Eggs of Southern African Birds. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa. Close ).

Condition at Hatching

Captive day-old chicks weighed 45.2–57.2 g (mean 52.8 g, n = 7) (128 Smart, G. (1965). Body weights of newly hatched Anatidae. Auk 82:645–658. Close ), or 52.0–61.5 g (mean 56.5, n = 9) (25 Brown, L. H., E. K. Urban, and K. Newman (1982). The Birds of Africa. Volume 1. Academic Press, London, UK. Close ). A five-day-old captive chick weighed 60 g and had mainly dusky brown upperparts, broken by white blotches, and its underparts were white (7 Siegfried, W. R. (1966). On the post-embryonic development of the South African Shelduck Tadorna cana (Gmel.). Ostrich 37:149–151. Close ). The wing had a white bar and there were elongated white blotches on the sides of the back immediately behind the base of the wings. There were also two large white patches on the rump near the base of the tail. The cheeks and sides of the neck were white, continuing without interruption to the chin, throat and breast, and over the abdomen to the tail. The maxilla was blackish gray, tipped pale gray, and the mandible was blackish gray tinged olive and tipped pink. The iris was dusky brown, the legs and feet buffy brown, and the membranes and toes blackish gray. The chick resembled that of the Egyptian Goose (Alopochen aegyptiaca), except that it lacked the white supercilium of the latter species. It also differed in the darker color of its soft parts, and the white blotches on the lower rump and wing were larger, as was the ‘egg-tooth’.

Growth and Development

The first contour feathers appear at ca. 18 days in the flanks and tail in captive chicks (7 Siegfried, W. R. (1966). On the post-embryonic development of the South African Shelduck Tadorna cana (Gmel.). Ostrich 37:149–151. Close ). 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 wing-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. At 42 days the head and neck had gray feathers (as in the adult male) and contrasted distinctly with the tawny-orange lower neck and breast. At 49 days female chicks had narrow white rims around the eyes and base of the bill, whereas these regions were uniformly gray in males, which in addition had paler-colored breasts. Between 49 and 77 days 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. While flightless, wild chicks dive to escape predators (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close ). Flight is possible at ca. 70 days in captive chicks (7 Siegfried, W. R. (1966). On the post-embryonic development of the South African Shelduck Tadorna cana (Gmel.). Ostrich 37:149–151. Close ) and wild chicks take approximately 60–75 days to achieve adult size and flight capabilities (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close ). Families apparently separate when the young are about 90–120 days old (92 Taylor, J. S. (1957). Notes on the birds of inland waters in the eastern Cape Province with special reference to the Karoo. Ostrich 28(1):1–80. Close ).

Both members of a pair lead the chicks to water, usually in the early morning (1 Geldenhuys, J. N. (1980). Breeding ecology of the South African shelduck in the southern Orange Free State. South African Journal of Wildlife Research 10:94–111. Close ). Both sexes also subsequently care for the young, which are kept in muddy areas with shallow water, unless disturbed when family parties take refuge in deeper water (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close ). Both pair members vigorously chase large birds, e.g., herons and cormorants, away from their chicks.

Information needed.

Brood parasitism by other waterfowl species has not been recorded.

Information needed.

Information needed.