Kalahari Bigfoot - encounter with an ostrich

As I approached the ostrich’s nest, I noticed from afar that the large, black cock-bird was incubating, which struck me as unusual since it is true that the drab female sits on the eggs during the day when her grey plumage gives her a remarkable resemblance to a termite mound. That is, providing she lowers her periscopic neck and lays it flat along the ground (this cryptic behaviour undoubtedly being the origin of the fable that the ostrich buries its head in the sand at the approach of danger!).

The male had also noticed my approach, but far from attempting to keep a low profile, he jumped up and, raising himself to his full height of over 2 metres, approached me in a most intimidating manner with feathers fluffed out and wings spread. Although largely preoccupied with my predicament, I could discern several small chicks amidst the gleaming white eggs in the nest-scrape. Now it dawned on me that the chicks were hatching, and the male had prolonged his normal nocturnal duties in order to protect the defenceless young.

This was not entirely unpredicted since I had found the nest eight weeks previously when it contained half a dozen eggs, which were being added to daily prior to the onset of incubation (which only commences when the clutch is complete). Surprisingly, ostrich eggs are not camouflaged like those of other ground-nesting birds and are thus not difficult to find. It is apparently more important for the eggs to be white to reflect heat, as some will be left uncovered under the early summer sun for up to three weeks before the start of incubation. This way, hatching of the chicks 45 days later will be synchronized and the parents can leave the nest site with the whole brood simultaneously. It was this event that I had wished to witness and which had led to my current, hazardous situation. During the incubation period, I had refrained from visiting the nest, although I had observed a curious feature once the clutch had been completed – some eggs were noticeably smaller than the others. I asked an ostrich farmer friend how this could have come about, and his explanation, based on his own observations, is quite extraordinary: when the dominant pair in an area start a nest, other subordinate females lay their eggs in the same nest – they are often young birds and, just like domestic chickens, their first eggs are considerably smaller than normal. Apparently the dominant female, which somehow knows her own eggs, arranges the others around the periphery of the nest so that in the event of predation by a hyena, hers are least likely to be taken.  Since the minor females may or may not have been mated by the dominant male, this breeding system has interesting implications for natural selection and the survival of the ‘fittest’ genetic types.

However, these scientific niceties were furthest from my mind during the confrontation with the fearless ostrich male! Vivid in my memory is a pair of powerful thighs atop bony legs terminating in lethal-looking, two-toed feet! Should I break a thorn branch with which to keep it at bay, or should I lie prone and be subjected to 100 kilograms of irate ostrich bouncing on my back? Instinct took over, and without reason, I sprinted away, hoping to outrun a bird with a top speed in excess of 70 kph! Fortunately it did not give chase, but the experience gave me yet another insight into the survival strategy of this unique bird.

Some weeks later, I saw the same pair of ostriches, but much to my surprise, they had 49 chicks in tow, despite the fact that their clutch had comprised 21 eggs, only 16 of which had hatched. Although the chicks seemed to fall into three distinct size classes, I was at a loss to explain how this could have come about until a few years later when I witnessed a struggle between two pairs in the Central Kalahari Game Reserve, with the victors kidnapping the vanquished pair’s entire brood. Again this is difficult to explain in terms of conventional evolutionary theory, although there is some obvious merit in the strongest pair caring for most chicks.

Thus I came to appreciate that the ostrich’s uniqueness extends way beyond its inability to fly.  It has many interesting adaptations to its terrestrial lifestyle, both physical and behavioural. Now when traveling through the dry savannahs of Botswana I always look out for this big bird, and marvel at how it has managed to survive without being able to fly.

Photo: Hannelore Bendsen

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