Diet and Foraging

Main Foods Taken

Seeds, aquatic plants, insects, crustaceans.

Microhabitat for Foraging

At wetland sites, these bird forage in open muddy areas with scattered short aquatic plants. They also feed in agricultural crop fields and fly up to ca. 50 km to reach these, i.e. 100 km round-trips, with such foraging round-trips made in the early morning and repeated in the afternoon from the waterbodies where they otherwise spend most of the day and roost overnight (102 Siegfried, W. R. (1967). Trapping and ringing of Egyptian Geese and African Shelduck at Vogelvlei, Cape. Ostrich 38:173‒178. Close , 28 Geldenhuys, J. N. (1977). Feeding habits of South African Shelducks. South African Journal of Wildlife Research 7:5–9. Close ).

Food Capture and Consumption

Flocks feeding in crop fields tend to be larger than those foraging on aquatic foods (28 Geldenhuys, J. N. (1977). Feeding habits of South African Shelducks. South African Journal of Wildlife Research 7:5–9. Close ). When feeding in the water, dabbling, scything, and head-dipping are the most common foraging techniques, with upending occasionally seen, scything and digging is used on exposed mud, and pecking is employed when foraging on dry ground (28 Geldenhuys, J. N. (1977). Feeding habits of South African Shelducks. South African Journal of Wildlife Research 7:5–9. Close ). The species also feeds at night, especially when molting (2 Shewell, A. L. (1959). The waterfowl of Barberspan. Ostrich Supplement 3:160–179. Close ), and frequently makes nocturnal flights (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close ).

Major Food Items

A detailed study in the Free State Province (28 Geldenhuys, J. N. (1977). Feeding habits of South African Shelducks. South African Journal of Wildlife Research 7:5–9. Close ) found that during winter and spring the species was entirely vegetarian, feeding mainly on seeds of maize (Zea mays) and sorghum (Sorghum bicolor) in harvested crop fields, and to a lesser extent submerged aquatic plants, e.g., algae (both filamentous Zygnemeceae: Spirogyra, Zygnema and Cladophora, and macroscopic Chara and Nitella) and Lagarosiphon. During the midsummer (molting) period, flocks were reliant on wheat (Triticum aestivum) seeds, although some individuals appeared to largely fast during the flightless period, with only small amounts of food found in the gizzards of flightless birds, e.g., algae, Odonata, ants, beetles, and praying mantises probably taken from the water surface as molting birds do not come ashore. In late summer and autumn they fed mainly on animal matter, chiefly crustaceans (Conchostraca and Notostraca) and, especially, tendipedid larvae and pupae, with lesser volumes of ostracods. Plant food at these times included Chara, Nitella, Spirogyra and, especially, Zannichellia. Animal food consumed during the pre-breeding period may be important in stimulating nesting (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 ). Algae, e.g., Spirogyra, were also noted in the species’ diet in the Eastern Cape Province (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close , 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 ). Common sunflower (Helianthus annuus) is another crop plant recorded in the diet (104 Reynolds C. (2016). The role of waterbirds in the dispersal of aquatic organisms in southern Africa. Ph.D. thesis, University of Cape Town, Cape Town, South Africa. Close , 105 Reynolds, C., and G. S. Cumming. (2016). Defining functional groups using dietary data: Quantitative comparison suggests functional classification for seed-dispersing waterfowl. Basic and Applied Ecology 17(4):333–343. Close ).

Only Branchiopoda (Phyllopoda) were found in the stomachs of six individuals; the notostracan (Apus numidicus) (30–40 mm long) comprised 96% by volume and a conchostracan (Caenestheriella sp.) the balance, along with grit in the form of sand grains and worn pebbles (106 Siegfried, W. R. (1965). Branchiopoda (Phyllopoda) in the diet of the African Shelduck. Ostrich 36:146. Close ). Orthopterans have been recorded in the diet (107 Kok, O. B., and S. M. Louw (2000). Avian and mammalian predators of orthoptera in semi-arid regions of South Africa. South African Journal of Wildlife Research 30:122–128. Close ). A captive male fed on grain, bread and scraps, preferred moist items, was noted to wet its food prior to ingestion, and frequently foraged on growing clover and dandelion flowers (22 Taylor, J. S. (1944). Notes on the South African Shelduck. Ostrich 15:188–193. Close ). Chicks feed largely on submerged aquatic vegetation, e.g., Spirogyra and Lagarosiphon (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 ). This species has been grouped with Egyptian Goose (Alopochen aegyptiaca)and Spur-winged Goose (Plectropterus gambensis) as ‘grazing ducks’ with an emphasis on their importance as potential seed dispersers (104 Reynolds C. (2016). The role of waterbirds in the dispersal of aquatic organisms in southern Africa. Ph.D. thesis, University of Cape Town, Cape Town, South Africa. Close , 105 Reynolds, C., and G. S. Cumming. (2016). Defining functional groups using dietary data: Quantitative comparison suggests functional classification for seed-dispersing waterfowl. Basic and Applied Ecology 17(4):333–343. Close ), but this is somewhat misleading as there is no evidence that the species feeds on grass (3 Maclean, G. L., and G. Darroll (1986). Ducks of Sub-Saharan Africa. Acorn Books, Johannesburg, South Africa. Close ).

Information needed.

Information needed.

Information needed.

Information needed.