Rock Kestrel

264 Falconidae: falcons and kestrels

brooding young. Therefore the small increase in reporting rates in six of the eight Zones during winter is probably related to seasonal changes in conspicuousness, rather than to any large- scale influx of migrants from outside the region. Reporting rates for the Tarkastad district, for example, increased during winter, while direct observation showed that over half of the population actually left the area (Van Zyl 1994b). Although the models do not suggest movements within southern Africa, a more detailed analysis of Rock Kestrel movements in South Africa, largely based on a more refined examination of atlas reporting rates, suggested a northerly and easterly movement away from south- western breeding areas during winter (Van Zyl et al. 1994). Breeding: Breeding was recorded in all Zones, mainly September–January, peaking October–December. There are no obvious seasonal differences between the Zones, although in the eastern Cape Province (Zone 8) it bred slightly later than in the rest of the region. Interspecific relationships: It overlaps widely with Greater and Lesser Kestrels in southern Africa. It moves into the eastern grassland habitats most exploited by the Lesser Kestrel during the winter when that species is absent (Van Zyl et al. 1994). Historical distribution and conservation: Boshoff et al. (1983) found no difference in distribution in the Cape Prov- ince, comparing the periods 1700–1969 and 1970–79. The distrib- ution map similarly shows no change in distribution, the species being largely absent from the central Kalahari regions and the far northeast during all three time periods, although the map shows Rock Kestrel many more records from the western Karoo, presumably due to Rooivalk better coverage. The Rock Kestrel is the most common of the small breeding falcons in southern Africa and it cannot be con- Falco tinnunculus sidered threatened. It has adapted well to humans, even breeding on buildings (Mendelsohn 1990). Its distribution has probably The Rock or Common Kestrel is a widespread species found changed little because its principal habitats are little altered by throughout most of the Old World. The southern African popu- agriculture; however, large-scale poisoning of locusts is likely to lation belongs to the race F. t. rupicolus. Although it was recorded have a considerable influence on local population numbers. from all the countries of southern Africa, the distribution map shows marked differences in abundance, reflected in reporting A.J. van Zyl rates, in different regions. It is most abundant in western Namibia, southern and western South Africa and Lesotho. It is less com- Recorded in 2582 grid cells, 56.9% mon, but still widespread in most of northeastern South Africa, Total number of records: 26 892 extending into western Swaziland. In Zimbabwe it is restricted to Mean reporting rate for range: 21.2% the high-lying central and eastern regions, and it occurs widely, but sparsely, in Botswana. It is scarce in northeastern Namibia, central and northern Kalahari, and the tropical low-lying regions Reporting rates for vegetation types of Zimbabwe, the Limpopo Valley, the eastern Transvaal low- % 0204060 veld, and northern KwaZulu-Natal. The Transvaal population was estimated to be in excess of Alpine Grasslands 54.0 1000 pairs (Tarboton & Allan 1984) with densities of at least Succulent Karoo 46.4 2 pairs/100 km2 in prime habitat. Breeding densities of 19 and 29 Grassy Karoo 42.1 pairs/100 km2 were measured in the Tarkastad district (3126CC) Nama Karoo 41.9 (Van Zyl 1993). Namibian Escarpment 35.8 The Rock Kestrel is a relatively easy bird to identify although it Fynbos 29.3 may be confused with the Greater Kestrel F. rupicoloides and Southern Kalahari 25.1 especially the male Lesser Kestrel F. naumanni (Steyn 1982b). Namib 23.6 Habitat: The large number of vegetation types in the vegeta- Valley Bushveld 21.5 tion analysis reflects the wide variety of habitats exploited by this Sweet Grasslands 20.9 versatile species. The highest reporting rates came from the Alpine Mixed Grasslands 20.3 Grasslands, Karoo and Fynbos regions, and the species appears Sour Grasslands 13.8 capable of inhabiting the entire span of arid to mesic conditions Central Kalahari 13.8 in the region. The distribution, especially for breeding, is strongly E Zimbabwe Highlands 11.1 influenced by the distribution of mountainous areas. Arid Woodland 8.9 Movements: It is highly conspicuous as it often hunts from Moist Woodland 6.1 roadside telephone poles and electricity pylons (Steyn 1982b). Mopane 5.5 However, it uses such structures less frequently during the breed- Miombo 4.5 ing season, when it tends to hunt closer to nest sites, usually Northern Kalahari 4.0 situated on cliffs. In addition, the visible breeding population is East Coast Littoral 4.0 also effectively halved when females are incubating eggs or Okavango 2.6 Falconidae: falcons and kestrels 265

14û

ROCK KESTREL 5 1 18û

22û 2 6

26û

3 7 30û Reporting rate (%) > 34.3 16.7 — 34.3 2.0 — 16.6

< 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

Occurrence reporting rate (%) 40 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: 323, 815, 1481, 3018, 260, 639, 2594, 1504; Breeding: 6, 6, 30, 56, 6, 19, 18, 64.