The African Skimmer

The African Skimmer

An African skimmer on the sand banks of the Chobe.

Birdwatching is a wonderful hobby. It usually begins as a pleasant diversion, perhaps something to occupy you when there are no animals to be seen on a safari. But before you can say ‘What’s that LBJ?’ (little brown job), you will be hooked. Particularly if you take the time to do a little research. You will find that many of the birds are absolutely fascinating, with intriguing habits and memorable anecdotes about each species. Be warned – birding can easily become an obsession which makes ticking the big five look positively pedestrian. On my last visit to Chobe, we were lucky enough to come across a breeding pair of African skimmers (Rynchops flavirostris). I managed to get a couple of halfway decent images of the pair and decided to use them as the subject for this week’s newsletter.

This bird has an incredible bill – with the lower mandible being longer that the upper. The lower mandible is triangular in cross section and fits into a groove in the shorter upper mandible. It flies back and forth, low over the water, with its sensitive lower bill cutting the water and closing (powered by strong neck muscles) as soon as it detects a fish. The fish is swallowed, with no discernible alteration in wing beat rhythm – then the process begins again. 

The African skimmer’s bill is very distinctive.

These birds ‘feed by feel’. In most birds, taste and touch are not particularly well developed. That said, the degree of sensitivity in the bill and tongue depends on how the bird feeds. Researchers have found that birds relying on their beaks for foraging have tongues and bill tips that are densely packed with sensitive receptors known as ‘Herbst corpuscles’ which are sensitive to both taste and touch. This sensitivity in the bill allows these birds to locate potential food only by touch, and to know whether it is edible, without having to see it. 

The African skimmer also has vertically slit pupils. This cat-like pupil dilates widely to enhance the eye’s light-gathering properties, enabling the skimmer to feed in the poor light of dusk and dawn. These same pupils can also narrow to five percent of the dilated pupil to reduce the light reception during the day when the bird must deal with the glare off the white sandbanks under the blazing sun. This protects their retinas from sun damage.

Adults remove eggshells from the nest.

These birds are considered partial intra-African migrants. Their arrival and departure times coincide with the falling and rising river levels. These skimmers breed along the slow-flowing sections of the Chobe, Zambezi, Okavango and occasionally other rivers. The sandbars become exposed during low-flow periods (Aug – Nov), and they arrive in these areas during June. From Aug to Nov, they nest singly or in small groups of up to 20 – although three to five is more common. A few remain from January to April, especially in drought years. Their non-breeding grounds are likely in the Rift Valley, as far North as the Equator. 

 They nest on bare, dry sand, usually within 20m of the water’s edge, less than half a meter above the water line and mostly on islands. These sites are re-used year after year, provided they remain undisturbed and free of vegetation. They are simply a deep scrape in the ground (150 – 250mm in diameter and 50 – 100mm deep) where two to three eggs are laid. Neighbours may be within 10-20m of each other. African skimmers are known to cool their eggs by wetting their belly feathers – a practice known as ‘belly-soaking’. This is a response to ground temperatures being incredibly hot – which increases the chances of their eggs overheating and becoming non-viable.

A particularly bold little chap…

Populations are decreasing rapidly due to habitat loss. For example, the construction of Lake Kariba led to the loss of breeding sites both up- and down-stream of the dam wall. There have been no breeding records in the area subsequent to the flooding of the lake in 1963. The wakes of boats cause huge destruction of nesting sites and loss of eggs. Local children collect eggs as food and chicks as fishing bait. In some areas canoe safaris camping on the islands disturb the birds. In other areas the introduction of alien species such as Nile Perch may also reduce their food supply. Herons and monitor lizards are also a threat to the eggs and the chicks. Human disturbance at breeding colonies can cause nest failure if the adults are kept off their eggs or young during the incredible heat of the day. These birds are currently having a hard time…

The young stay in the nest scrape for about two days. When they hide, they are almost impossible to see. They dig themselves into the sand to avoid detection, and only fly when 5-6 weeks old. They’re brooded and fed by both sexes of the monogamous pair. 

I hope you enjoyed this little read and learned something new to boot. If you think this hobby may be of interest to you, grab a pair of binoculars and start looking at our feathered friends. You don’t have to go far – even your garden will do…

Jacqui Ikin & The Cross Country Team


African Skimmer Parenting:

African Skimmers:

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