Archive for June, 2011
Bird of the Week – Week 75 – Cape cormorant
June 12th, 2011 | 
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Posted in If you sit somewhere along the Namibian west coast, particularly in the vicinity of Swakopmund, and look out over the Atlantic Ocean at sunrise or sunset you are bound to see long chains of dark coloured birds flying in single file just above the water, heading to or from their overnight roosts. These are Cape cormorants, near endemic to the southern African coast and very common along this stretch of coastline, although they are considered to be “near threatened” because their numbers have declined rapidly in recent years.
The Cape cormorant is a medium sized cormorant, with a length of about 63 cm; the males are a little larger than the females. They are almost entirely glossy blue-black, with an orange throat patch. The bill is dark grey; the eyes turquoise and the legs and feet are black.
The Cape cormorant, also known as the Cape shag, very often forages in large flocks, feeding on schooling fish, such as pilchards and anchovies.  They generally forage 10 to 20 km out to sea, although they can often be seen closer than this, sometimes just beyond the breaking waves.
Cape cormorants are usually silent when away from the roost, but utter a nasal grunt when disturbed while at rest.
Cape cormorants are monogamous, but are colonial breeders and the males defend their nesting sites vigorously. One of the popular breeding sites is a guano platform that has been erected near Swakopmund. Their nests are untidy piles of sticks, bones, seaweed, feathers and other material, including human debris. The female lays a clutch of between one and four eggs that hatch after an incubation period of about 25 days.
The scientific binomial for the Cape cormorant is Phalacrocorax capensis; Phalacrocorax from the Greek for “bald raven” and capensis from the Latin for “from the Cape (of Good Hope)”. Well, from the Cape of Good Hope I can understand, but a Bald Raven?
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Oxpeckers – Heroes or villains?
It seems as though the jury is still out on whether the oxpecker is a hero or a villain.
It is true that the oxpecker scavenges ticks off a wide variety of the larger African mammals, which is probably a good thing, but it also picks at any wounds or sores on the host animal to keep them open and bleeding, which is probably a bad thing. Indeed, the favourite food of the oxpecker is blood. Many of the ticks that it feeds on are engorged females, which have already fed on the blood of the host animal, and have therefore already caused whatever harm they are likely to cause in terms of drinking blood and spreading disease. Too late to help the host, but great for the oxpecker! The open wounds also provide access to all manner of infections. Although the relationship between the oxpecker and the hosts used to be considered of mutual benefit, there is a growing tendency to regard the bird as a parasite offering little benefit to the host.
There are two varieties of oxpeckers found in the southern African region – the Red-billed oxpecker and the Yellow-billed oxpecker.
Red-billed oxpeckers (Buphagus erythrorhynchus) are medium-sized passerines, with a length of about 20 cm. They have brown upperparts and heads, buff underparts and pale rumps. Their bills are red, the eyes are red or yellowish and they have yellow eye rings. They nest in holes in trees, which they line with the hair that they have plucked from their hosts. The females lay a clutch of two to five eggs, which hatch after an incubation period of around twelve days.
Yellow-billed oxpeckers (Buphagus africanus) are very similar in size and plumage colouration to the Red-billed variety, but have a yellow base to their red-tipped bill and a pale rump. They also lack the conspicuous yellow eye ring. Breeding habits are similar.
Sinners or saints, the oxpeckers are interesting little birds. They feed almost exclusively on the backs of larger mammals, not limiting themselves to a diet of ticks and blood, but also taking dead skin (finally a use for dandruff!!), mucus, saliva and even ear wax.
On a recent visit to the Kruger National Park in South Africa we witnessed Red-billed oxpeckers making themselves at home on a variety of different species. Some hosts appeared almost indifferent to their presence, whilst others tried actively to unsettle the birds by flicking their ears, swishing their tails, stamping their feet or generally making it difficult for them to retain their perches. The oxpeckers, for their part, seemed oblivious to the discomfort that they wrought as they pecked into the host’s ears (after that ear wax!) or perched on the host’s face.
Few of the larger animals seemed immune to the oxpecker’s attentions and they even settled on hippos as they emerged from the water.
Bird of the week – Week 74 : White-browed scrub-robin
The White-browed scrub-robin, with a length of around 15 cm, is much the same size as the other scrub-robins and out in the field it is often necessary to look at the birds quite carefully to identify them with any certainty. The sexes are alike in both size and plumage colouration. The upper parts are light brown and they have conspicuous white eyebrows and two white wingbars; rump is orange- rufous; the tail blackish tipped with white; under parts are white, breast and sides streaked with black. Bill is black, eyes brown and legs and feet pinkish-grey.
The White-browed scrub-robin is quite common preferring woodlands and patches of acacia, and is usually found in pairs. In southern Africa its range is restricted to the wetter western part of the region, and it is also found outside the region as far north as Ethiopia.
It feeds mainly on insects and spiders, favouring termites and ants, foraging on the ground by running forward a few steps and flicking its tail as it pauses to pick at an insect. The White-browed scrub-robin also forages through piles of leaf-litter in its hunt for food.
The call of the White-browed scrub-robin, like that of the robins generally, is quite melodious, consisting of a series of whistled phrases. It often sings from a branch low down within a thicket and can be surprisingly hard to see even when it can be heard close-by.
White-browed scrub-robins are monogamous and construct a deep cup nest of grass lined with finer grass, often locating it in the grass at the base of a tree. The female lays a clutch of two to four white eggs that hatch after an incubation period of approximately 12 days.
The scientific binomial for the White-browed scrub-robin is Cercotrichas leucophrys; Cercotrichas from the Greek for a “long tailed thrush” and leucophrys from the Greek for “white eyebrow”. Thus a long tailed thrush with a white eyebrow, which is quite an apt description, as the scrub-robins were at one time classified as part of the thrush family.
Waterbuck – A shaggy buck story
Visit any of the game reserves in southern Africa and you are sure to see loads of buck of every description, especially impala and springbok. Whilst it’s great to see the common buck, it’s always a thrill to come across the more unusual ones, like the Waterbuck, which is very distinctive with its long shaggy coat and a target-like white circle arounds its tail.
We saw some in the Kruger National Park, but they are popping up in various odd locations as they’re being sold to private nature reserves and game farms.
Waterbuck (Kobus ellipsiprymnus) are large antelope that prefer to move around in small herds of between 5 and12 animals. Males and females tend to stay in separate herds, with the females guarding their calves and young ones. Males are very territorial and often have lethal fights for dominance in the herd. The sexes are easy to distinguish as the females are much smaller and don’t have horns.
Their habitat is in dry floodplains and areas close to water, although Waterbuck, as their name might imply, are not aquatic animals like the lechwe or sitatunga. They do, however, take to water when in danger, even if crocodiles are present. Waterbuck have a number of predators (spotted hyena, wild dogs, lions and cheetahs), but they have a rather unpleasant smelling secretion from their skin (to waterproof their fur), which sometimes deters their attackers.
Calves are born throughout the year, usually singly, and take about three and a half years to reach maturity. The mother licks the baby after it suckles to remove its characteristic odour and confuse predators. But in spite of this, they have a high mortality rate. Numbers are kept up by females mating within six weeks of giving birth, and calves are born after a gestation period of about nine months.
Waterbuck eat grass, fruit and leaves and drink a lot of water. If they can escape being part of the food chain, they can live up to fourteen years.
