Diet, body mass and condition of Lesser Kestrels Falco naumanni in South Africa

Diet of the Migrant Lesser KestrelsFalco naumanniin their Winter Quarters in South Africa

“…Our data, based on stomach contents from birds in their winter quarters, suggest that this is only partly true as approximately two fifths of the animal component by dry mass (39.3%) consisted of arthropods other than insects, notably solifugids and centipedes. Compared to the diet of breeding birds (Franco & Andrada 1976), the general lack of vertebrate prey during the wintering season is also striking, an aspect also mentioned by McCann (1994) and Anderson et al (1999). This discrepancy can probably be attributed to the higher energy demand during breeding, necessitating the predation on prey-groups with relatively high biomass (Glutz von Blotzheim et al 1971, Cramp & Simmons 1980, Rudolph 1982, Village 1990, as well as the occurrence of courtship feeding involving vertebrate prey (Franco & Andrada 1976, Cade 1982.…”

“…This indicates that the birds concerned chose food items available in large quantities on which they could gorge themselves. Indications are also that large discrepancies in the annual occurrence frequencies of prey items within the same invertebrate orders can be related to local variation in the relative abundance and availability of prey (Anderson et al 1999). The fact that orthopterans were predominantly consumed during late summer implies that larger-sized prey are involved in fat deposition and the consequent increase in body mass (Kok & Van Zyl 1996, Anderson et al 1999 prior to the birds' northward migration to their breeding grounds.…”

“…Indications are also that large discrepancies in the annual occurrence frequencies of prey items within the same invertebrate orders can be related to local variation in the relative abundance and availability of prey (Anderson et al 1999). The fact that orthopterans were predominantly consumed during late summer implies that larger-sized prey are involved in fat deposition and the consequent increase in body mass (Kok & Van Zyl 1996, Anderson et al 1999 prior to the birds' northward migration to their breeding grounds. By maintaining a high and rapid turnover in biomass, southern African grassland habitats seem ideally suited to support migratory birds of prey, especially insect-eaters, during the austral summer, a phenomenon also reported on by Moreau (1972) and McCann (1994).…”

“…This discrepancy can probably be attributed to the higher energy demand during breeding, necessitating the predation on prey-groups with relatively high biomass (Glutz von Blotzheim et al 1971, Cramp & Simmons 1980, Rudolph 1982, Village 1990, as well as the occurrence of courtship feeding involving vertebrate prey (Franco & Andrada 1976, Cade 1982. Lesser Kestrels are opportunistic (non-specialist) foragers with great potential to feed on locally and temporally abundant invertebrate food sources (Anderson et al 1999). This is well illustrated by the marked monthly variation in their dietary composition which hints at a possible relationship between the abundance of different prey species and the frequency of their capture.…”

Seasonal and annual dietary changes in Lesser Kestrels Falco naumanni wintering in Lesotho

“…1999, Kok et al 2000. Food composition was determined by means of stomach content analysis (Kopij 1998, Anderson et al 1999. Kok ef al.…”