|Pel's Fishing Owl|
|Range:||n-e Namibia, n South Africa, nw Zimbabwe|
|Area of occupancy:||3,562 km2|
|Population estimate in Namibia:||< 120 birds|
|Habitat:||Large rivers, quiet backwaters|
|Threats:||Degradation of riparian woodland, hydro-electric schemes, wood-cutting|
Distribution and abundance
Click to see distribution map
This much sought-after owl is the largest of Africa's three Fishing Owls (Kemp & Kemp 1998). It is an uncommon, nocturnal resident found across tropical rivers throughout central w Africa, and Zambia and Mocambique (del Hoyo et al. 1999). In southern Africa it is sparsely distributed only in the n regions in the Okavango Delta, n South Africa and n and se Zimbabwe at a reporting of 8% (Mendelsohn 1997). It is rare in Namibia, with birds only found along the Okavango, Kwando and Zambezi Rivers (Mendelsohn 1997), covering an area of occupancy of 3,562 km2 (Jarvis et al. 2001). Populations are estimated at <500 prs for s Africa (Mendelsohn 1997) and 60 prs for South Africa (Barnes & Parker 2000). High densities of 3.8 prs/10 km in the Okavango (Liversedge 1980) and 4.4 prs/ 10 km in the n Kruger Park (Tarboton et al. 1987), suggest that populations on the last 50 km of the Okavango River (20 prs) and 60 km of the 155 km-Zambezi River (25 prs) are unlikely to exceed 45 prs (~120 mature individuals) in Namibia. This is about 9% of the regions' population. On the Okavango River birds may be most likely where overhanging trees still occur at Andara and Max Makushe (M Paxton pers obs). Because fish populations and the number of suitable trees in occupied habitats in Botswana and South Africa are likely to be higher than in Namibia (JM Mendelsohn pers obs) populations in Namibia may be lower than this even in prime habitat.
Prefers large overhanging trees within 50 m of the riverbanks in which to roost and from which it forages over and into nearby pools. It prefers the slower moving large rivers to small and fast flowing rivers, especially backwater pools where perhaps fish are more visible or it is safe from the depredations of it chief competitor the African Fish Eagle (Liversedge 1980). It may first concentrate and subsequently move from these areas as the pools dry up (concentrating then eliminating the fish) and then it may be found in unusual locations such as farm dams (Mendelsohn 1997, Barnes & Parker 2000). It nests in hollows and forks of large trees with (2) eggs being laid in a peak from February-April (Skinner 1996) in the Okavango. There are four breeding records from Namibia (Jarvis et al. 2001) three of which were from April, May and June when it is likely that the calling of still dependent fledglings gave the nesting area away. The Okavango River is then at its peak flow (Mendelsohn & el Obeid 2004) suggesting birds time their breeding to peak availability of backwater pools and spawning fish.
Its food comprises almost exclusively medium to large fish, which are caught after dusk and before dawn (Liversedge 1980). Only a single youngster is reared which leaves the nest almost 4 months after eggs are laid (Liversedge 1980). There are no data on breeding success.
Population trends are unknown for this large owl, but it has almost certainly suffered riverine forest degradation and in future may suffer from water regulation in the Okavango River. This may occur as natural water levels and flooding is disrupted downstream of the proposed Divundu hydro-electric diversion weir on the Okavango River. Human population pressure on the Okavango River is as high as anywhere in Namibia (Mendelsohn & el Obeid 2004) and as a consequence fishing pressure there is intense (Hay et al. 2000). This has led in some areas to a depletion of fish populations and a degradation of the overall biotic integrity of the river (Hay et al. 1996). The only areas known to be unaffected by fishing and wood cutting on this river occur in sanctuaries such as Mahango Game Reserve (Hay et al. 1996), comprising the last 20 km of river. Even within the Mahango Game Reserve habitat quality is likely to have declined given the high density of elephants that have destroyed large areas of suitable trees (M Paxton pers obs). The effect of this human pressure and disturbance became apparent when guerilla activity starting in 1999 forced local inhabitants to move away from their Okavango River homes. Within months, monitoring of the wetland bird populations indicated a twofold increase in species richness and a three-fold increase in abundance (M Paxton in Simmons 2003). Fish populations rebounded similarly (C Hay unpubl data), neither of which were associated with any above average river flow in 1999/2000 (Mendelsohn & el Obeid 2004) which might also explain the rapid increase. Given that Pel's Fishing Owls will be affected by depressed fish populations and the clearing and cutting of large trees, their habitat has clearly been degraded and will continue to decline in quality with a high human growth rate.
This species is designated as Critically Endangered because of the small population size of less than 120 mature individuals with an inferred decline of 25% over the last generation of this long-lived species (C1). Both factors arise from the continuing degradation of riparian vegetation on all rivers, especially the Okavango and Zambezi. This may lead to the birds eventual extinction in Namibia because of the rapidly growing human population (doubling every 23 years), with the densest concentrations along the large northern rivers (Mendelsohn et al. 2002). Even within the protected areas such as Mahango both fish populations and suitable nest trees are under pressure from upstream activities (over-fishing, and soil erosion from the cutting of trees) and the high elephant populations. Despite its small overall representation in Namibia, this owl is likely to come under pressure in many riparian areas of Africa as the continent becomes drier under global change scenarios (IPCC 2001, Midgley et al. 2001) and human populations migrate towards the region's rivers. This may happen in all except perhaps the largest wetland reserves (eg the Okavango Delta) or further afield in the Congo River basin.
It is not threatened globally (Birdlife International 2004) but it is designated as Vulnerable in South African Red Data assessments based on the same small localized populations and degradation of habitat outside reserves (Barnes & Parker 2000).
The most urgent need for this species as a large sensitive flagship icon for riverine birds is a conservation area on the Okavango which protects both the fish and the large riparian trees on which it depends. The Mahango Game Reserve satisfies some of these criteria but burning regimes and elephant populations also need to be managed to preserve suitably large nesting trees. The Zambezi River that runs through Namibia from Katima Mulilo to Kasane, has no protected sections at all and riparian woodland near Katima and eastwards at Impalila island with their high bird species diversity (Mendelsohn & Roberts 1997) would both be prime candidates for woodland reserves.
Research, using recorded voice playbacks (Kemp & Kemp 1989), is required to establish breeding densities in Namibia and to understand which areas need to be given priority and protection. This is especially true of the Kwando River which should support owls, but does so apparently only sporadically (Mendelsohn 1997), and the Impalila woodlands at the junction of the Chobe and Zambezi Rivers near Kasane. None were recorded in the 24 yr bird atlas period (Mendelsohn 1997), but one was subsequently recorded there shortly there after (R Randall in Mendelsohn 1997) suggesting it may be overlooked elsewhere too. While all these areas fall within the East Caprivi Important Bird Area (Simmons et al. 2001) the IBAs conveys no formal protection.
From: Simmons RE & Brown CJ 2006. Birds to watch in Namibia: red, rare and endemic species. National Biodiversity Programme, Windhoek, Namibia
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Hay, Clinton Fisheries biologist, Ministry of Agriculture, Water and Rural Development (firstname.lastname@example.org).
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