South African Shelduck Tadorna cana Scientific name definitions

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

Diet and Foraging

Feeding

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, 28).

Food Capture and Consumption

Flocks feeding in crop fields tend to be larger than those foraging on aquatic foods (28). 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). The species also feeds at night, especially when molting (2), and frequently makes nocturnal flights (22).

Diet

Major Food Items

A detailed study in the Free State Province (28) 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). Algae, e.g., Spirogyra, were also noted in the species’ diet in the Eastern Cape Province (22, 92). Common sunflower (Helianthus annuus) is another crop plant recorded in the diet (104, 105).

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). Orthopterans have been recorded in the diet (107). 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). Chicks feed largely on submerged aquatic vegetation, e.g., Spirogyra and Lagarosiphon (103). 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, 105), but this is somewhat misleading as there is no evidence that the species feeds on grass (3).

Food Selection and Storage

Information needed.

Nutrition and Energetics

Information needed.

Metabolism and Temperature Regulation

Information needed.

Drinking, Pellet-Casting, and Defecation

Information needed.

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
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