Evidence of partial migratory behaviour by the Cape Griffon Gyps coprotheres

Abstract

Migratory behaviour has been reported for several Old World vulture species, but not for the Cape Griffon (Cape Vulture) Gyps coprotheres. Analysis of opportunistically obtained Cape Griffon distributional data from the Eastern Cape province of South Africa showed that griffon location was dependent on time of year, corresponding to the breeding season (April–October) and the non-breeding season (November–March). This finding was corroborated by a survey of landowners/ managers in the so-called East Cape Midlands, wherein 59% of respondents who reported the occurrence of griffons had a level of interest and awareness that enabled them to note seasonal occurrences; all stated that the griffons were observed ‘only, or mainly, during the summer’, i.e. during the species’ non-breeding season. Further corroboration was provided by the results of systematic counts (over 12 consecutive months) at two roost sites in the Midlands area. At both sites, the griffons were absent during the autumn–winter period (breeding season) and present during the spring–summer period (non-breeding season). Since only a portion of the Eastern Cape population appears to migrate, the species is considered a partial migrant. The source of the griffons that migrate to the Midlands area is not known. The possible origins of the reported migratory behaviour are discussed.