African Fish Eagle Visarend Haliaeetus Vocifer

Accipitridae: vultures, kites, hawks, eagles, buzzards and harriers 205

African Fish Eagle Visarend Haliaeetus vocifer

An Afrotropical species, the African Fish Eagle is fairly It is usually recorded singly or in pairs, but occasionally widespread in the higher-rainfall east and extreme south in flocks of up to 75 birds, e.g. in the Okavango Delta and southwest of southern Africa. Concentrations of high (Pryce 1990). It can occur at high densities under suitable reporting rates were associated with the eastern and south- conditions. The highest recorded density in the atlas region ern coastal regions (estuaries), major rivers, such as those is along the Boro River in the Okavango Delta where in the Transvaal lowveld and the Limpopo and Zambezi breeding pairs are about 400–500 m apart (Brown 1980). rivers, and on the main floodplain systems, such as the In a wider survey of 761 km of the Okavango, Linyanti, Okavango, Linyanti and Chobe rivers. In the dry west, it Chobe and Boteti rivers in northern Botswana, an average extends along the entire length of the Orange and Vaal density of 1 bird/1.9 km of river frontage was measured rivers, and into the central regions of Namibia, where it is (M. Herremans unpubl. data). At Lake Kariba, densities of presumably associated with large dams, such as Hardap 1 bird/3–6 km have been recorded (Irwin 1981; Eriksson Dam (2417BD). The association with high rainfall and & Skarpe 1989), while occupied nests were 1.9–3 km apart wetlands is due to its diet of fish and waterbirds. Locally (Douthwaite 1992c). On the Zambezi River, linear densi- its occurrence is patchy, owing to the nature of its habitat. ties of 1.1–3 km were observed, and territories were 2.8 km 206 Accipitridae: vultures, kites, hawks, eagles, buzzards and harriers apart on average (Ewbank 1991; Francis et al. 1992). In the The conservation status of the African Fish Eagle is Transvaal lowveld, inter-pair distances ranging from 5– reasonably sound. Some populations have been negatively 11 km have been recorded (Tarboton & Allan 1984). It is impacted by disturbance, development and wetland degrad- conspicuous and adults are easily identified. ation, especially in coastal areas and along lakes and rivers Habitat: It is associated with estuaries, coastal and inland (e.g. Douthwaite 1992c). Balancing this, artificial impound- lakes, larger rivers and pans, floodplains and artificial im- ments have provided additional habitat. Critical levels of poundments. Immature birds have been recorded at smaller eggshell thinning, caused by the ingestion of DDT, have dams, marshes and even sewage works. It can occasionally been exceeded in certain localities (e.g. Douthwaite be found far away from water. When temporary rivers of 1992c). As yet there is no firm proof that it is threatened the Okavango dry up (e.g. Boteti, Kunyere, Thamalakane, by organochloride residues (Davies & Randall 1989), but Boro), Fish Eagles remain for prolonged periods with no the situation should be monitored. Breeding populations standing water, and prey on birds (e.g. doves and sand- may be limited by the availability of safe nest sites (Douth- grouse) or feed on livestock carcasses (M. Herremans pers. waite 1992c). comm.). A.F. Boshoff Movements: The models show increased reporting rates in the north of the range coinciding with the breeding season when the eagles are territorial and conspicuous. Immatures and subadults disperse widely from their natal areas (Brown et al. 1982). A late-summer/early-winter influx of immature birds has been recorded in the southern Cape Province (Boshoff & Palmer 1988a); this may rep- resent an annual congregation. Breeding: Atlas records came from throughout the range, mainly during the period May–February, with a variable late-winter/early-summer peak. The models suggest a slightly later season with increasing latitude. Egglaying Reporting rates for vegetation types peaks have been recorded for April–June in Zimbabwe, % 04080 May–June in Botswana and the highveld and lowveld areas of the Transvaal, and June–August in the south (Brown et Okavango 66.4 al. 1982; Tarboton & Allan 1984; N.J. Skinner in litt.). East Coast Littoral 40.2 Historical distribution and conservation: There has Mopane 34.9 not been any apparent change in distribution in the Cape Miombo 23.3 Province (Boshoff et al. 1983) but it is now more wide- Arid Woodland 23.3 spread, especially in arid areas, as a consequence of the Moist Woodland 20.0 building of large dams. Overall, the current distribution is Valley Bushveld 19.1 considered to reflect the historical distribution. Fynbos 17.7 Northern Kalahari 16.2 E Zimbabwe Highlands 13.0 Grassy Karoo 10.4 Succulent Karoo 8.2 Central Kalahari 8.1 Recorded in 1379 grid cells, 30.4% Sweet Grasslands 7.9 Total number of records: 23 967 Nama Karoo 7.6 Mean reporting rate for range: 23.1% Sour Grasslands 7.3 Mixed Grasslands 5.9 Namibian Escarpment 1.2 Accipitridae: vultures, kites, hawks, eagles, buzzards and harriers 207

14û

AFRICAN FISH EAGLE 5 1 18û

22û 2 6

26û

3 7 30û Reporting rate (%) > 32.7 11.8 — 32.7 2.0 — 11.7

< 2.0 34û 4 8 18û 22û 26û 14û 30û 10û 34û

40 1 5 40 20 20

40 2 6 40 20 20

40 3 7 40 20 20

40 Occurrence reporting rate (%) 4 8 40 Breeding reporting rate (%) 20 20

J ASONDJ FMAMJ J ASONDJ FMAMJ Models of seasonality for Zones. Number of records (top to bottom, left to right): Occurrence: 510, 59, 327, 599, 2667, 2726, 2162, 635; Breeding: 17, 4, 13, 69, 112, 150, 89, 20.