SBA #9: Danger . . . Goose - Toxic and Armed!
The cache is the 9th of 9 caches placed within this special place - regarded by birders as the one of the best birding sites in the Western Cape. Thanks are due to the Supervisor of the False Bay Nature Reserve for kind permission to places caches here.
The cache, a small flip-topped dispensing pot, is hidden on the edge of Pan 3 from where a small group of these impressive large water birds were observed feeding in the neighbouring Pan 2 across the track.
To reach the cache location:
a) To reach the centre starting point of SBA: use the waypoints for GC846D9 Strandfontein Birding Area #1: Bird Info Centre to reach the multi-junction at the hub of the spokes of tracks leading between the pans. Then proceed with b) or c) as desired.
b) Direct from the Information Centre: head straight across here (ie. 3rd exit coming from the SBA entrance gate) heading south-west between P2 & to the cache location.
c) If following the cache sequence: fromGC846EP SBA#8: Flamingone? return to the junction @ S 34 05.173 E 18 30.405 turn left (north-east) and continue between Pans P2 & P3 to the cache location. From here continue to the hub and onwards to the SBA exit
The spur-winged goose (Plectropterus gambensis) is a large bird in the family Anatidae, related to geese and shelducks, but distinct from both of these in a number of anatomical features. It occurs in wetlands throughout sub-Saharan Africa.
Adults are 75–115 cm long and weigh on average 4–6.8 kg, rarely up to 10 kg with males noticeably larger than the females. The wingspan is 150-200 cm. They are the largest African waterfowl and are, on average, the world's largest wild 'goose. They seem to be more closely allied to shelducks than 'true geese'.
They are mainly black, with a white face and large white wing patches. The long legs are pinkish red in colour. The nominate race P. g. gambensis has extensive white on the belly and flanks, but the smaller-bodied subspecies P. g. niger, which occurs south of the Zambezi River (and is therefore the one seen at SBA, has only a small white belly patch and from a distance can appear all black.
The male differs from the female, not only in size, but also in having a larger red facial patch extending 
back from the red bill, and a knob at the base of the upper mandible.
It is generally a quiet species. Typically, only males make a call, which consists of a soft bubbling cherwit when taking wing or alarmed (listen here). During breeding displays or in instances of alarm, both sexes may utter other inconspicuous calls.
Some populations of this bird may be poisonous due to a diet of blister beetles. The poison, cantharidin, is held within the tissue of the fowl resulting in poisoning of those that eat the cooked goose. 10 mg of cantharidin can kill a human. For those unfortunate enough to do this, the phrase 'your goose is cooked' meaning 'you are in big trouble' would be particularly appropriate.
It often occurs in open grasslands with lakes, seasonal pools, rivers, swamps and river deltas. Large inland rivers and lakes are most commonly inhabited, with saline lakes and upland areas generally being avoided, although it can occur up to 3,000 m asl in eastern Africa. It is also absent from arid zones.
It is gregarious, generally meeting in small flocks of up to 50 birds. Varied sites may be used for post-breeding moulting, when large numbers of the geese may congregate. It feeds by grazing, but spends the middle part of the day resting by water. It may perch in trees to roost.
Its diet is mainly plant matter such as the vegetative parts and seeds of grasses, sedges and aquatic plants, agricultural grains, fruit (eg. figs) and tuberous crops, although it may occasionally supplement its diet with small fish or insects. Dispersal may occur in pursuit of feeding opportunities outside of the breeding season.
The breeding season varies across its range - in southern Africa it is from August to May. It is highly aggressive to other waterfowl during breeding when the geese may violently use the sharp spur (an outgrowth of bone covered in a sheath of horn) on the bend of the wings in conflicts with other birds. Adult males in particular tend to attack other males.
Its large nest is usually concealed in vegetation near water in quiet, undisturbed stretches of riverbank and wetlands. Tree holes, cavities in rocks, old hamerkop, African fish eagle or social weaver nests and even the top of a termite mound and an aardvark burrow have been used as nest sites. When choosing a tree-nest site, they usually select a location close to the ground 20-100 cm up in trees 3-4 m high. It prefers for nest sites.
It is a common bird of African wetlands. The main threat facing it is development and destruction of wetland habitats and unregulated hunting - in Nigeria it is hunted and traded at traditional medicine markets.
See here for a good collection of videos and photos of this bird and here for a short video which clearly shows the spurs on the wings.