EVIDENCE FOR SEASONAL MOVEMENTS BY ROCK KESTRELS FALCO-TINNUNCULUS AND LANNER FALCONS F-BIARMICUS IN SOUTH-AFRICA

Patterns of seasonal movement by Rock Kestrels Falco tinnunculus and L anner Falcons F, biarmicus in South Africa were determined using data from the Southern African Bird Atlas Project, road transect; counts, r inging recoveries and other sources. Both species were found to be par tial, facultative migrants, and Lanner Falcon movements involved mostl y immature birds. Rock Kestrels were found to concentrate in the south west of the country in the breeding season, and to move north and east in the non-breeding season. Lanner Falcons concentrated in the east o f the country during the breeding season, and moved into the west in t he non-breeding season. The movement by both species into the arid nor thwest of the country is probably associated with dramatic increases i n prey abundance, in turn associated with summer rain events. Lanner F alcon movement into the southern Cape apparently coincides with cereal farming practices, affecting the availability of prey (granivorous bi rds and rodents). Rock Kestrel movement into the east of the country i s probably to exploit increases in insect abundance associated with su mmer rain. The pattern of Rock Kestrel movements suggests that it does not compete for food with the Lesser Kestrel F. naumanni, a Palearcti c migrant to the east of the country.