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Secretarybird Eagles, Buzzards and Harriers

Secretarybird Eagles, Buzzards and Harriers

152 : ,: kites, , , buzzards and harriers

Nylsvley (2428DA) numbers fluctuated widely and population shifts may occur in other areas, e.g. the Transvaal highveld and lowveld (Tarboton & Allan 1984). Breeding: The models indicate that breeding takes place throughout the atlas area, in all months, except in southern areas (Zones 4 and 8) where breeding was not recorded in midwinter. They also show a breeding activity peak July–January. These patterns generally concur with published accounts, including peak egglaying dates (Cyrus & Robson 1980; Brown et al. 1982; Tarboton et al. 1987b; Hockey et al. 1989; Maclean 1993b). Historical distribution and conservation: There has not been any apparent change in distribution in the Cape Prov- ince (see Boshoff et al. 1983). Locally the may have increased its abundance as a result of extensive bush-clearing programmes. Overall, the current distribution is considered to reflect closely the historical distribution, and any changes are likely to be in abundance rather than distributional limits. Several Secretarybird areas with particularly high reporting rates correspond with large Sekretarisvoël conservation areas, e.g. , Kalahari Gemsbok Park, Hwange National Park and Etosha. If these are representa- Sagittarius serpentarius tive of its ancestral abundance, then the species may have under- gone a massive decrease outside such areas. The Secretarybird is an Afrotropical species occurring through- Its provides cause for concern. It is sensi- out the atlas region. The map shows interesting patterns of abun- tive to habitat degradation due to overgrazing, , dance in different parts of its range. It occurs at low reporting rates disturbance and loss of habitat to afforestation and cultiva- in the southwestern Cape Province but is more common along the tion. Numbers may have decreased in the northwestern Cape south than the west coast in this region (cf. Hockey et al. 1989). Province and (Boshoff et al. 1983) and also in the south- In the eastern parts of South it is noticeably absent or rare western Cape Province since 1960, and particularly during the in the Lesotho highlands, in Transkei, along the east coast, in east- 1980s (Hockey et al. 1989). Bush encroachment is thought to have ern Swaziland, in the central highveld of the Transvaal, and along reduced the suitability of much of the Swaziland lowveld (Parker the Transvaal escarpment. In Transkei and the central Transvaal 1994). On the other hand, bush clearance has created additional highveld, high human densities probably largely exclude it, espe- habitat, for example in parts of the Transvaal, where the species’ cially as a breeding , and in Swaziland extensive bush conservation status is considered to be good (Tarboton & Allan encroachment is responsible for its scarcity (Parker 1994), particu- 1984). A survey is needed to determine the current conservation larly as it appears to be common in adjacent areas. The paucity status of the Secretarybird. of records from the Lesotho highlands, east coast and Transvaal A.F. Boshoff and D.G. Allan escarpment may be related to natural unsuitability of habitat. In Zimbabwe it prefers the central watershed regions compared with lower-lying adjacent regions to the north and south. It is wide- Recorded in 2034 grid cells, 44.8% spread in Botswana and Namibia but appears to avoid the Namib Total number of records: 15 792 Desert. Mean reporting rate for range: 13.7% Although the distribution map suggests that it is more common in the eastern half of southern Africa, compared with the western half, the models show little difference, suggesting that it is equally Reporting rates for vegetation types common in both regions and that better coverage in the east is % 02040 responsible for the larger number of records there. The models, however, do show a clear decrease in reporting rates from north Grassy Karoo 31.6 to south. Southern Kalahari 31.5 It usually occurs singly or in pairs, occasionally in par- Alpine 24.4 ties of 3–4 , with groups of up to 50 recorded at waterholes Mopane 22.2 in arid areas (Brown et al. 1982). Densities of 0.2–2.0 pairs/ Central Kalahari 16.2 100 km2 have been recorded at study sites in the Transvaal Miombo 15.1 (Tarboton & Allan 1984). Sweet Grasslands 14.8 Habitat: It chooses open country, mainly , open wood- Arid Woodland 13.8 land, and dwarf shrubland. These habitat preferences are Northern Kalahari 12.8 confirmed by the relatively high reporting rates in the Karoo, Kala- Nama Karoo 11.4 hari, Grassland, Mopane, Miombo and Woodland vegetation Mixed Grasslands 10.7 types. It is also attracted to man-made habitats such as airfields, Sour Grasslands 10.7 grazing paddocks and fallow fields. It is absent from mountain E Zimbabwe Highlands 10.4 fynbos, and avoids , dense woodland and very rocky, hilly or Moist Woodland 10.3 mountainous areas. Okavango 9.9 Movements: The atlas data do not reveal any regular seasonal Valley Bushveld 5.7 movements. The high monthly variation in the reporting rates in Namibian Escarpment 4.0 the arid westerly parts (Zones 1–3) suggests that the species is Fynbos 3.6 nomadic in low-rainfall areas. It is reported elsewhere to under- Succulent Karoo 2.8 take increased local movements outside the breeding season and East Coast Littoral 2.1 to be highly nomadic in arid areas (Brown et al. 1982). At Namib 1.8 Accipitridae: vultures,Sagittariidae: kites, hawks, Secretarybird eagles, buzzards and harriers 153

14û

SECRETARYBIRD 5 1 18û

22û 2 6

26û

3 7 30û Reporting rate (%) > 23.2 10.3 — 23.2 2.0 — 10.2

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

30 1 5 40 20 20 10

30 2 6 40 20 20 10

30 3 7 40 20 20 10

30 40 Occurrence reporting rate (%) 4 8 Breeding reporting rate (%) 20 20 10

J ASONDJ FMAMJ J ASONDJ FMAMJ Models of seasonality for Zones. Number of records (top to bottom, left to right): Occurrence: 374, 398, 474, 278, 1153, 911, 1512, 281; Breeding: 35, 7, 38, 22, 34, 54, 97, 36.

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