In steep decline

Conditions around the lake do not augur well for Naivasha’s buzzards, writes Munir Virani.

ikuyu people believe that if you see be among the most frequently seen of all the white chest of an Augur Buz- East African birds of prey. Kzard (Mwewe), Buteo augur, first My own research on Augur Buzzards thing in the morning, then your day will – beginning with a four-year study (1995– be a successful one. 1999) conducted at three sites around Augur Buzzards are medium-sized Lake Naivasha in Kenya – has revealed, hawks with short, stout bodies, broad not only that such a complacent attitude is wings, and striking, brick red tails. Until re- foolhardy and reckless, having no basis at cently, their presence over much of Kenya’s all in science, but also that it is downright central highlands – including moorland, ­irresponsible. forest verges, rock outcrops, and cultivated Why study a common species like areas – could easily be taken for granted. the Augur Buzzard? And why in the Lake An Augur Buzzard circling overhead was Naivasha area, of all places? simply part of the mise en scène of daily ru- The effects of rapid habitat change ral life, as was its characteristic squawking on an ecosystem are perhaps best gauged call. through studying the behaviour, not of a The species appears to have adapted highly specialised ‘niche’ inhabitant, but very well to human settlement, agricultural instead of a commonly seen and adaptable expansion, and exotic plantation forest. A species. Among such species, an aerial ‘apex’ ‘Not threatened’ conservation status, then, predator – like the Augur Buzzard, which has always seemed assured. Indeed, some operates near the top of the food chain – is field guides declare the Augur Buzzard to often the most instructive barometer of

20 SWARA April – June 2006 case study an area’s general ecological health. This is ­riparian land-use were affecting Augur because the health of its ‘umbrella’ popula- Buzzard ecology and behaviour. I made tion generally mirrors that of other species daily observations of the buzzards in 40 at the lower trophic levels. As such, there is identifiable territories spanning the Hell’s a correlation between a flourishing raptor Gate National Park (HGNP), the various population and a healthy and biodiverse commercial horticultural establishments environment. (mainly flower farms) located between The Naivasha area has – as we all know the park and the southern lakeshore, and – been subjected to a period of accelerated Mundui, a privately owned expanse of Aca- habitat change with the expansion along its cia woodland. shores of Kenya’s burgeoning cut flower in- I found that Augur Buzzards within the dustry, buoyed by access to plentiful ‘free’ HGNP preferred to nest on cliffs, whereas water from the lake, cheap labour, and at Mundui and in the horticultural fields proximity to the Kenyan capital, Nairobi. they chose trees. Male Augur Buzzards in The lake’s enormous economic impor- the HGNP spent significantly more time tance is reflected in the fact that 75 % of incubating and attending to chicks than all the cut flowers produced in Kenya (now did their counterparts outside the park. Europe’s third largest supplier, after Hol- This may have been because there are more land and Israel) are grown on its shores. predators – such as baboons, other eagles, Between 1978 and 1998 Kenyan exports of and crows – to contend with in the park. cut flowers increased ten-fold (from 3,000 In the HGNP, the larger, more aggressive tonnes to 30,000 tonnes). Since then, the female Augur Buzzards were kept busy industry has continued to expand apace, defending nests, leaving the males to look raising questions over the sustainability of after the eggs and chicks, or risk breeding uncontrolled water extraction from Lake failure. (Size differences between the sexes Naivasha, destruction of riparian habitats, in raptors – an evolutionary phenomenon pesticide run-off, influxes of labour, the known as reversed sexual dimorphism resulting proliferation of lakeside settle- – may help to reduce competition between ments, and so on … males and females, while also enabling The implications are understandably pairs to exploit both large and small prey dire for Lake Naivasha’s ecological status species within an occupied territory.) as one of Africa’s – and the world’s – most important wetland areas. As home to more ugur Buzzards in the HGNP were than 350 bird species, the lake is ranked feeding on a variety of prey: from among the top bird watching destinations Aflushes of dung beetles during the on earth. Its shores provide essential corri- long rains, to birds, reptiles, and small dors for wild ungulates. Incredibly (in view mammals. Buzzards in the commercial of what is going on there), the lake is also a horticultural areas fed almost exclusively Ramsar Site (that is, a wetland recognised, on mole rats, and occasionally field mice. according to criteria adopted at a milestone Mole-rat populations have boomed in the conservation convention in Ramsar, Iran, volcanic soils of the horticultural areas, in 1971, as being of global importance on presumably in the absence of mole snakes the strength of the water birds and other and other natural predators that were extir- wild species it supports, as well as for its pated with the introduction of agricultural scientific, cultural, and recreational value mechanisation. to people). In the privately owned woodland of A scientific understanding of the envi- Mundui, tall and mature Acacia trees Within the past ronmental consequences for Lake Naivasha combined with good grass cover and abun- of the horticultural industry’s runaway dant prey produced a significantly higher six years, Augur growth, not to mention a host of other number of chicks per year (1.3 annually, problems (notably those arising from the on average) than the other habitat types. Buzzard territories introduction of a succession of invasive Although the HGNP is a protected area, species, from the Louisiana Freshwater Augur Buzzard pairs there produced only around Lake Crayfish to the Water Hyacinth), is crucial one chick every two years, a reflection if this important lake – and with it, the maybe of the high predation pressure from Naivasha have well being of a large riparian human popu- baboons and other nest raiders, as well as declined by lation – is to prosper. A study of the Augur fiercer competition with rival predators. Buzzard’s behaviour and ecology around Overgrazing by huge populations of between 33 % Lake Naivasha, then, might be expected to ungulates has changed the characteristics provide some answers. of the grass cover in the HGNP, which and 57 % in all To this end, I geared my research in turn has negatively affected prey abun- to finding out how different aspects of dance and availability. Hunting success habitat types.

SWARA April – June 2006 21 rates for Augur Buzzards were lower inside Preliminary results show that Augur the HGNP than in the horticultural fields Buzzard territories around Lake Naivasha and at Mundui. have declined by between 33 % and 57 % Did this mean Augur Buzzards in in all habitat types. the prey-rich horticultural areas raised Predictably, the steepest decline in the more chicks? Certainly not! When mole- number of territories has occurred on, or rat numbers peaked in June, soon after near, flower farms, and in areas accommo- the long rains, many of the farms would dating large, and rapidly growing, human deliberately seek to eliminate them, either populations. Loss of previous foraging through direct poisoning or by employing grounds (now invariably replaced by flow- casual workers to kill them, thus depriving ers), destruction of nesting sites, increased growing chicks of food. human persecution, and a greater likeli- Although Augur Buzzards were pres- hood of electrocution are clearly some of ent in good numbers at all three Naivasha the principal reasons behind the alarming sites, I collected 15 dead adult birds over decline I observed in the number of Augur the four-year period. Annual adult mortal- Buzzard territories around Lake Naivasha. ity on the horticultural farms I estimated at A decline of 50 %, or more, in the pop- 13 %. This suggested that the area might ulation of any commonly seen bird of prey be acting as a ‘population sink’ – meaning is almost imperceptible to casual observers. that, while Augur Buzzards may have been (In the early 1990s, when it was proposed dying rapidly, they were being replaced by that the conservation status of three South a ‘floating’ population of birds waiting to Asian Gyps vulture species be up-listed to occupy territories. the ‘Endangered’ category, there was laugh- Persecution by humans and electro- ter all around the conference hall – until, cution through contact with overhead that is, a team of researchers presented transmission lines were the major causes of ­irrefutable scientific data showing how adult mortality in the horticultural areas. the species’ respective populations had, in Other causes of death included poison- ­reality, fallen by as much as 90 %!) ing (direct and indirect) and drowning in Similarly, from Leslie Brown’s pioneer- cattle water troughs. ing studies in the early 1970s, we know that Lake Naivasha’s population of another he findings of my 1995–1999 study ‘common’ species – the African Fish Eagle, have contributed to a more thorough Haliaeetus vocifer – has fallen by more than Tscientific understanding of Augur 50 % over the past 35 years. Again, as Buzzard ecology and behaviour. Perhaps with the Augur Buzzard, this decline has more significantly, however, this study has not been readily apparent, as African Fish yielded valuable baseline data from which Eagles are still commonly seen (and heard) it is now possible to assess the impact of on the lake, where their population may commercial horticulture’s subsequent ex- even be said to have stabilised in the past pansion around Lake Naivasha. couple of years – albeit on the back of an Over a two-week period in October explosion, post-El Niño, in Lake Naivasha’s 2005, I revisited all 40 Augur Buzzard population of that most recent of alien territories I had observed and monitored invaders: the carp. Any short-term stablili- between 1995 and 1999. In particular, I sation, then, while encouraging, must be wanted to find out what effect continuing viewed in the wider context of the species’ expansion of Lake Naivasha’s horticultural worryingly low overall population base. and related riparian developments were So, while I am not suggesting any up- having on the species’ food supply and listing in the conservation status of the ability to nest … Augur Buzzard (or, indeed, in that of the I considered a territory to be occupied African Fish Eagle), I can state categorically where I could see either one or a pair of that a population decline of between 33 % Augur Buzzards soaring above it, or where and 57 % within six years in the prevalence Dr Munir Virani coordinates the Asian Vulture a previously documented Augur Buzzard’s of a species that is as resilient and versatile Crisis Project for The Peregrine Fund. He also nest showed signs of breeding activity or as the Augur Buzzard does not augur well carries out research on raptors in Kenya in recent use. In 20 % of all cases, I could for the ecological health of the Naivasha association with the National Museums of Kenya. recognise individual buzzards from rings, area. And that is putting it very mildly! The Augur Buzzard Project served as the basis of his PhD thesis at the University of Leicester in the or from known markings (distinctive Adaptability in a species may reach a UK. This Project was funded through grants from colour morphs or facial patterning). I con- threshold beyond which that species simply The Peregrine Fund, the Earthwatch Institute, and sidered a territory to be unused, defunct, can no longer go on adjusting its behav- the Aga Khan Foundation. The author gratefully acknowledges the assistance he has received or abandoned where I saw no Augur Buz- iour and ecology. Lake Naivasha’s Augur over the years from the Lake Naivasha Riparian zards at all over a period of at least three Buzzards appear, alas, to have reached this Association. consecutive days. critical point – of no return.

22 SWARA April – June 2006