| Bateleur | |
| Terathopius ecaudatus | |
| Status: | Endangered |
| Range: | Botswana, Namibia, n South Africa, Zimbabwe |
| Area of occupancy: | 258,430 km2 including 2,074 km of border rivers |
| Population estimate in Namibia: | c 1130 prs, or (maximum) 3000 birds |
| Population trend: | 50% decline in last 3 generations |
| Habitat: | Mopane, Kalahari and arid savanna woodlands |
| Threats: | Poisons, declining prey base, human disturbance at nests |
Distribution and abundance
 Click to see distribution map |
This species is widely distributed across West and East African woodland savannas, absent from tropical rainforests and appears again in central-s Africa, but is largely absent from South Africa except for its northern parks (Tarboton & Allan 1984, del Hoyo et al. 1994, Simmons 1997). It requires very large territories (Tarboton & Allan 1984, Watson 1986), so it is nowhere abundant.
From historical records from the 1900s it is clear that this unmistakable species has undergone massive range reductions in South Africa (Boshoff et al.1983), shrinking into large protected areas such as Kruger Park and the Kalagadi Trans Frontier Park (KTFP) (Watson 1988, 1990). Estimates of the previous South Africa population size have been made of 2500 prs (Boshoff et al. 1983, Steyn 1982), a figure that now stands at 600 prs for the former Transvaal (Tarboton & Allan 1984), 22 prs for the KTFP (Herholdt & de Villiers 1991) and 8-10 pairs outside it (Anderson 2000a). This represents a 75% reduction in numbers, suggesting similar reductions in numbers in Namibia because of similar threats (see below). Populations in s Mozambique number c >1,600 birds (Parker 1999).
No density estimates are available for Namibia but reporting rates from bird atlas data in Etosha NP are similar to the Kruger NP (<50%), suggesting similar densities, including adjacent conservation areas (Simmons 1997). There nesting density varies from 2.2 -3.3 prs/100 km2 (Tarboton & Allan 1984, Watson 1990, Simmons 1994). Outside these areas density drops to c 0.2 -1.0 pr/100 km2 in unprotected areas (Tarboton & Allan 1984).
In Namibia it is absent from the south and west, thinly spread in central-east farmlands, relatively common in Etosha and former Ovambo, and most common in the wetter Kalahari broad-leafed woodlands of the Caprivi (Simmons 1997). The area of occupancy in Namibia is 34,049 km2 in protected areas and 224,425 km2 in unprotected areas (Jarvis et al. 2001). An approximate population figure using the minimum densities derived from protected (2.2 prs/100 km2) and unprotected areas (0.2 prs/100 km2) in South Africa projected over these areas of occupancy, gives 680 prs in protected areas and 450 prs in unprotected areas of Namibia. The total population is 1,130 prs or about 3 000 birds. They are almost certainly declining given the level of poison abuse in Namibia (Komen 2002), and the high rate of scavenging vultures poisoned (mean 21/yr in the 7 yr period 1995-2001: Bridgeford & Simmons unpubl data).
Ecology
Found in open and closed-canopy savanna woodlands, including Acacia savanna, Mopane and miombo woodland (Brown et al.. 1982, Steyn 1982, Tarboton & Allan 1984); commonest in broad-leaved woodland in Okavango Delta where reporting rate are > 60% (Simmons 1997). Rarely occurs in heavily forested, mountainous or largely treeless habitats (Tarboton & Allan 1984). In Namibia found most often over tall woodland near drainage lines and dry rivers in Caprivi and within the more arid Etosha NP (Simmons 1997).
Feeds on a variety of prey including mammals, birds and reptiles. It kills and scavenges during long distance foraging, and its ability to locate very small pieces of carrion makes it highly susceptible to poison-laced carcasses (Brown et al. 1982, Tarboton & Allan 1984, Watson 1988. Also pirates prey from other species (Watson & Watson 1987).
This eagle is a solitary, tree-nesting, species with a very large home range of 21-40 km2 (Tarboton & Allan 1984). Nest densities are unknown in Namibia but average c 5 km apart in the densest nesting areas in ne South Africa (Tarboton 2001), and 13-16 km apart in Zimbabwe (Steyn 1982). Egg-laying records for Namibia are sparse but laying occurs virtually year-round from Jan (1), Feb (1), March (1), April (1), July (1), Nov (1), December (2) (Brown & Clinning unpubl data). The rate of success in Namibia is unknown but averages 0.47 - 0.58 y/pr/yr in protected areas in South Africa (Watson 1986, Tarboton & Allan 1984), and 0.81 y/pr/yr at 4 nests in Zimbabwe (Steyn 1982).
Threats
Suffers direct persecution through poisoning at both large and small carcasses (Watson 1986). Because it forages over wide areas it covers many farms and thus it is at risk from even a small proportion of farmers who use poisons in Namibia (Brown 1991) and South Africa (Davies 1988). Birds occur outside protected areas in central and northern farming areas and communal lands, probably because these hold fewer small stock farmers who lay poison baits for mammalian carnivores (Brown 1986). Farmers frequently use poisons on the edge of conservation areas such as Etosha NP (Komen 2002) regularly killing vultures there (Bridgeford & Simmons unpubl data, T Osborne unpubl data). While Bateleurs are not recorded they almost certainly succumb as young birds disperse from these "safe" breeding areas. Poisoned Bateleurs are found within other protected areas in South Africa (Herholdt et al. 1996).
Breeding pairs are more often unsuccessful than successful due to predation and human interference (Watson 1988) including sensitivity to desertion at the egg stage (Steyn 1982). While traditional healers use vulture parts in Namibia there are no current records of Bateleurs being caught and killed (Hengari 2002). Some birds are trapped for use by traditional healers in S Africa because feathers are used for predicting future events (R Watson, P Steyn unpubl data).
Poisons may not account for all reductions in population density. This is apparent from the highest densities occurring in protected areas with intact wildlife populations, despite poisons not being used in the surrounding regions (e.g. Okavango Delta and Chobe NP: Simmons 1997). This suggests that the removal of large ungulates from cattle farming areas, reduces food available for Bateleurs, especially carrion for young birds (Steyn 1982, see also Martial Eagle), ultimately reducing their numbers. Habitat destruction and pesticides (DDT residues) have also been suggested as reasons for reductions (Steyn 1982) but DDT residues found in eggs are too low to account for the population declines (Watson 1986), and there is limited evidence for habitat destruction per se.
Conservation status
This species is classified as Endangered because of a suspected decline of at least 50% in the last 3 generations (~30 yr). This rate is based on two comparisons (i) the feeding-ecology similarity of this species with the Tawny Eagle, which in central Namibian farmlands declined by 71% (7 prs to 2 prs) in just 6 years (Brown 1991). These two species are more susceptible to poisons than any other raptors (Steyn 1982, Tarboton & Allan 1984, Watson 1986); (ii) the decline in Bateleurs in South Africa which was estimated at 75% over the last few decades (above). As a long-lived species, rarely laying 1 egg every year (Watson 1986), the Bateleur like other slow-maturing, slow-breeding species is unlikely to recover quickly from depressed adult populations.
It is not classified as globally threatened (Stattersfield & Capper 2000), but in South Africa it is classified as Vulnerable because it is thought to have lost 20% of its range in the last 3 generations through poisoning and direct persecution (Anderson 2000a).
Actions
Decreasing the frequency of abuse of poisons is one essential ingredient in preventing further population declines in all scavenging species (Watson 1987).
There are opposing viewpoints on the way forward. One proposal is to ban completely the poisons used for killing small carnivores from the Namibian environment (Brown 2002). This view advocates that (i) it sets a standard that using poisons for killing predators is unacceptable and not in the national interest (ii) it will cause the thinking farmer to choose other, more environmentally friendly methods; and (iii) when poisons were banned in western Europe vulture populations showed a remarkable recovery. To add to this it has been shown that Diclofenec which is as lethal to vultures in India as strychnine is to scavengers in Africa (Oaks et al. 2004), need only occur in 0.13 to 0.75% of all carcasses in the environment to cause a 30% annual decline and eventual population crash of Indian vultures (Green et al. 2004).
The opposite view is that the total ban is (i) impractical (ii) threatens the agro-chemical industry and (iii) is too idealistic to work (Verdoorn & Komen 2002). Concentrating on stopping abuse and working with farmers to apply poisons responsibly, is seen as the only way forward.
In Namibia it is apparent that awareness campaigns and farmer education programmes have not stemmed the tide of poisonings in Namibia, because poison abuse continues to kill commoner scavenging species (Bridgeford & Simmons unpubl data). The critical point is that all farmers need to be convinced of the need for sound farming and poison-free methods, given that it is estimated that 0.1% of the farming community is responsible for the decline (Brown 2002).
In some areas of South Africa it is claimed that Bateleur populations are increasing as a result of awareness campaigns (Anderson 2000b) but before-and-after evidence for this is lacking. For this reason, the draft Parks & Wildlife Management Bill (2002) will ban the use of poisons in predator control, and permits will only be given by the Ministry of Environment & Tourism for farmers to use poisons in exceptional cases. The Bateleur like other scavengers are Protected Species under this Bill. A research monitoring programme on (i) the success of awareness programmes elsewhere where the Raptor Conservation Group is intensively targeting farmers (ii) the success of the poison ban on scavenging raptor populations in selected parts of Namibia, and (iii) the density and breeding success of prs inside and outside conservation areas in Namibia is required to monitor this and other scavengers.
From: Simmons RE & Brown CJ 2006. Birds to watch in Namibia: red, rare and endemic species. National Biodiversity Programme, Windhoek, Namibia
References
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Bridgeford P, Simmons RE. Recent unnatural vulture deaths in Namibia 1995-2001. Unpublished data.
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Watson RT 1987. Bateleurs, poison and the future. Custos 15: 22-37.
Watson RT 1988 The influence of nestling predation on nest site selection and behaviour of the Bateleur. S. Afr. J. Zool. 23:143-149.
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