Evaluate the status of raptor diversity and abundance in Uganda
Objectives: To establish and sustain a cost-effective long-term baseline of raptor diversity and abundance and correlate this with habitat and land-use. To help develop local capacity in the field of raptor biology for Ugandans. To disseminate our findings via popular and scientific publications.
Uganda is a small country (some 220,000 km2), with a human population of between 30 and 40 million and has one of the highest population growth rates in the world. About 40% of the country is under agriculture, almost entirely smallholder farms of just one or a few hectares. Pastoral communities occupy a similar area, while the remainder consists of a variety of protected areas, together with swamps and lakes. The country has a very rich bird life, with over a thousand species recorded, including 72 diurnal raptors, of which three are globally threatened according to the IUCN Red Data List. With the increasing human population, and consequent changes in land use, we began looking at raptor communities as barometers of ecosystem health. This is because raptors occupy large home ranges, are on top of the food chain and offer themselves as effective bio-indicators to changes in habitat and land-use. For example, the population of Hooded Vultures in the city of Kampala has declined from an estimated 430 in 2005 to 276 in 2009.
Since 2007, The Peregrine Fund has supported three related projects carried out jointly by Makerere University and NatureUganda to study various aspects of raptor populations in Uganda. The largest of these has been road counts, first in 2008 and then in the three following years. The original idea of these was to repeat routes followed by the late great Leslie Brown who, whilst based in Kenya, made several visits to Uganda in the 1960s as a tour guide. For some of those journeys, he made careful counts of raptors seen along the way – presumably from the front seat of a minibus. He recorded his results meticulously in neat diaries, now kept at the Edward Grey Institute at Oxford University (UK), and summarized them in his book - African birds of prey. We have since added to the routes to get a larger sample, but on those roads which, to a large extent are those that he recorded, we have found that populations of two important groups – harriers and vultures – seem to have declined – whereas eagles, including snake eagles, have increased. We were particularly pleased (and surprised) to find an increase in Bateleurs and African Fish Eagles, two species in which Leslie Brown took a special interest, and this has made us wonder if our counts, usually including people on the roof of the vehicle or standing behind the cab of a pick-up, have seen more than he did, seated inside. Thus our comparisons have to be treated with caution. But the overall numbers are quite encouraging: in the national parks, where Leslie Brown recorded 53 raptors per 100km of road or track, we have had from 66 to 85 in the 5 years of counts to date. In unprotected areas, we have an average of about 40 per 100km, very similar to Brown’s 39. Even allowing for our better viewing opportunities, the differences over a 40-year period are not dramatic. However, in this fast-changing landscape and human population growth, it will be critical to continue monitoring raptor numbers and diversity, in order to inform policies that will result in scientifically sound management.
Although numbers of vultures have declined overall, their numbers are still significant. There are no known breeding colonies of vultures in Uganda (which is one source of evidence of their movements – they must breed somewhere!) so we conducted vulture counts at carcasses. In addition to a large number of opportunistic counts, we put out carcasses in 2003, 2009 and 2011, a couple of goats in 2003 and a cow in the later years, and in each case in all four savanna parks on the same day. In total these attracted 266, 290 and 319 vultures, respectively. If the apparent increase were real, that would be encouraging, but as with any counts there is an element of chance. For example, in 2011, there was a dead elephant near our site, and the local vultures were already gorged; some came over to look at the cow carcass, but none fed on it, and the number that came was doubtless boosted by the size of the elephant. However, by always using standard methods, we hope as the years go by that such chance events will not mask any overall trends.
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The emblem of the East Africa Natural History Society – now aged 102 – is the Long-crested Eagle. A study of this charismatic bird of prey in central Uganda is currently being made by two students; one Ugandan and one from the UK. Preliminary results show that that the bird is more common in agricultural areas than either national parks or pastoral areas. We are also assessing farmers’ attitudes towards the Long-crested Eagle – of more than 222 interviewed, 166 claimed that they knew the bird – but nearly 80% of those interviewed said that Long-crested Eagle eats chickens! Fortunately, we found little evidence of actual attempts to harm the eagles in return.