Colours of Wildlife: Spurwinged Goose
Created | Updated Dec 1, 2019
Spurwinged Goose
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
I have a spectacular bird for you today! This is the Spurwinged Goose, Plectropterus gambensis. The scientific name means 'spur-wing from Gambia'. It is not exclusive to Gambia (a small country in West Africa), actually occurring over all of sub-Saharan Africa, except for the driest deserts and the interior of dense rainforest. In South Africa it is not rare in the south, east and north, and I see it from time to time in the Polokwane region. Here I also show you a photograph of a quite tame one on the grounds of a casino! These birds are huge, reaching 1 m/39" in length and standing height, and 10 kg/22 lbs in weight.
Duck or Goose?
In ornithology, true geese form rather a small group among the Anatidae, the wildfowl family that includes ducks, geese and swans. The Spurwinged Goose is not a true goose; rather, it is a very big duck. It has been considered a relative of so-called perching ducks (which turns out to not be an actual clear, genetically-related group) and also of the shelducks (which also include species called 'geese' such as the soon-to-be-featured-here Egyptian Goose). It is very distinctive when seen: its size, glossy black colour and pinkish-red bill and legs set it apart from everything else. In Australia there's a similar, though not closely related, bird called a Magpie Goose, which actually forms on its own an outlying group pretty much equally distantly related to all other ducks, geese and swans.
There are two recognized races of spurwinged geese: ours, in Southern Africa, is very dark, while the northern race, found in the rest of Africa, has more white: on its face, on its belly, and on the trailing edges of its wings, the latter being conspicuous in flight. The northern race also has a sometimes quite tall knob on its forehead where the bill joins the rest of the skull, as if it was in a cartoon and had been bonked on the head with a hammer. (It is very interesting to me that a great many species of ducks, geese and swans have swellings or elaborate growths in this position, and appear to have evolved the feature independently on numerous occasions.) Both races have the feature the species is named for, a spur on its wing. This spur cannot be seen under most circumstances, being hidden by the feathers when the wing is folded. It is on the front 'bend' of the wing, corresponding to the human wrist. It is an outgrowth of the bones covered with a horny sheath, reaching 2 cm/0.8" in length. This spur is used in self-defense and fighting for dominance, territory and access to mates.
In their general habits, these are fairly inoffensive birds. They're mainly vegetarian, feeding on leaves, pods and corms of waterlilies and other aquatic plants as well as on soft plants growing by the river or lakeside. They do, however, sometimes make a nuisance of themselves by feeding in agricultural fields on plants the farmers don't wish to share. They are most often seen standing on the shore but sometimes they paddle along on the water surface like ducks. Their long legs also allow them to wade in shallow water in swamps and marshes. They are unusual among ducks for being able to roost in trees. They congregate in groups at roosts, flying off to feed each morning and returning in the evening. In flight, their huge wings make a loud whistling sound. They also have a whistling call, given as 'chick-wi, chick-wi, chick-wi' or 'cherwit, cherwit, cherwit' repeated numerous times.
Like many duck species, these birds moult their wing feathers once a year. This leaves them vulnerable to predators, so while the new feathers are growing out, they will congregate in the middle of large, open lakes or swamps. At the same time, they shed and replace the outer sheath of the wing-spur. Over this period they don't eat much and can lose up to a third of their bodyweight!
Most of the birds I've featured here so far are monogamous; spurwinged geese differ in that the male sometimes has more than one mate. But most of the time they, too, stick to a single partner. In the breeding season, the bare facial skin of the male becomes deep red to purple. He courts the female by perching on a stump, rock or anthill, fluffing up his feathers, flicking his wings and sounding his call. The two birds engage in swooping and pursuing courtship flights. The nest can be on the ground, in a hollow such as a tree cavity, a recess in a cliff or a hollow in an anthill, or a nest in a tree taken over from another large bird. It is lined with down, and the female lays six to 12 eggs in it. Sometimes more than one female lays in the same nest, up to a total of 27 eggs. Only the female incubates. She will cover the eggs with down and vegetation each time she has to leave the nest. The ducklings hatch after about 35 days. They're golden-brown with yellow stripes behind their eyes, and along their backs. They take to the water immediately, but their parents will keep them hidden amidst vegetation when they're still small. They take up to twelve weeks to fledge, but stay with their parents until the next breeding season.
Spurwinged geese are widespread and common in Africa, able to adapt to man-modified environments, even benefiting from farm fields and human-made ponds and lakes. They're hunted for food on a small scale. They're not endangered at present.
