Threatened Birds of Kenya - Kulal White-eye

Luca Borghesia and Kariuki Ndang'ang'a

White-eyes (family Zosteropidae) are a group of mostly tropical species, which despite their fragile appearance, have proved to possess an amazing ability for crossing hostile habitats and colonising far-flung places. As a result, the vast majority of the about 85 species are distributed on islands.

Although genuine 'islands' are scarce in East Africa, East African White-eyes have been able to find something quite similar. These are small forest fragments scattered in a 'sea' of arid or semi-arid environments. Such sites are numerous in Kenya and northern Tanzania, and have rightly been called 'forest islands' by several authors. Therefore, it's no surprise that the little yellow birds are found in on top of most of the mountains in our region! But here starts the problem: isolated populations tend to diverge from each other, slowly and inexorably, owing to what is called 'genetic drift'. As a consequence, white-eyes in East Africa comprise a large number of forms that differ in their appearance. Depending on one's point of view, these can be treated as separate species or simply a set of sub-species. The result is a sort of systematic wildness, where different authors have described as many as seven or as few as three species of Zosterops in Kenya and Tanzania.

One of these puzzles is the Kulal White-eye. Some consider it a good species, which should be called Zosterops kulalensis. Others prefer to treat is as a race of the Yellow White-eye (in which case, the correct scientific name should be Zosterops senegalensis kulalensis). Still others chooses to place it in the so-called Montane White-eye, and name it Zosterops poliogaster kulalensis. Nobody knows which of these possibilities reflects its real relationships. Indeed nobody knows much about this bird at all, except that it has an incredibly restricted range, on top of Mt Kulal, an extinct volcano east of Lake Turkana. We also know that the very small distribution almost automatically makes in an endangered taxon, because human pressure on the forest of Mt Kulal is increasing.

In November 1997 we reached the small village of Gatab, on the south slopes of Mt Kulal. We aimed at carrying out a survey of the avifauna of the area, and especially of its endemic white-eye. This was the start of forty days of very hard work, under the torrential rains caused by El Niño. Around us the ill-famed Chalbi looked more like a golf course than a lifeless desert... and on top of the mountain we had almost continuous rain and mist and high winds for all of our stay. Nonetheless we obtained some results and they were quite encouraging. Several white-eyes were mist-netted, and blood samples taken before they were released. DNA will be extracted from the blood and analysed and, providing (we hope) a clearer insight into the systematic status of these birds. This will take some time however! Meanwhile we collected a good amount of ecological and behavioural field data. First of all, as we saw, the white-eyes were common, perhaps the commonest species: almost one in four birds captured in the mist nets was a white-eye. They occurred in all habitats from 1500m upwards and estimates for the total population were in the order of 10,000 individuals... not bad!

Kulal White-eyes were quite varied in their food choice, as they ate fruit, nectar, insects, indeed every food item of appropriate size. We can be sure that they will not starve to death. Perhaps a more interesting discovery is that they were 'commuters'. They seemed to spend every night in the dense vegetation of the forest, but every morning huge flocks were observed at its edges, moving towards the drier habitats around, where they scattered in smaller groups that foraged among twigs. In the evenings they returned to the forest. It is not clear whether these movements occur all year round or perhaps only during the wetter months, when drier habitats become more productive. Still, we can confidently say that the white-eyes, at least for part of the year, are not completely dependent on the very restricted forest habitat.

On the whole, the highest densities of birds were found in the open forest, that is areas with typical forest trees (such as Juniperus and Olea) but a low and discontinuous canopy. Lower densities were observed in the very dense and tall vegetation and in the drier bushlands dominated by Acacia. In the forest, white-eyes clearly preferred glades and openings to places with a more continuous canopy. So they seemed mostly to be an edge species, and this certainly has important consequences from the conservation point of view. Human activity on Kulal at present seems to be causing a slow thinning of the forest. Glades are being opened in dense habitats and edges are generally increasing. This means that impacts on white-eyes, at least until now, have probably been limited, as their preferred habitat is still available, indeed on the increase. But as time passes, human population, firewood extraction, felling of trees for honey gathering and cattle pasturing are steadily growing, and will certainly cause the death of the forest if no action is taken. How much time is left? We don't know, but from experience elsewhere , probably not much.

What are we to conclude? Well, there is still time for action, but the time will expire soon. The forest of Kulal is of prime importance, not only for its endemic birds, but also for the people living in it, and they are now many. Sustainable exploitation is probably still possible now, if the right measures are put in place... will they be?

The above article is copyright, and reproduced by kind permission of, Kenya Birds magazine - a joint publication of the Department of Ornithology, National Museums of Kenya and the Bird Committee of the East Africa Natural History Society (EANHS).

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