Comparison of time-activity budgets and population structure for 18 large-bird species in the Kruger National Park, South Afric

Abstract

The activity, age, sex and group size was recorded for 10 177 instantoneous samples of 18 species of large (> 1 kg) birds in the Kruger National Park, South Africa, during 1991–94. The samples (75–2816 per species) were compared for four foraging guilds, of terrestrial (4 spp.), predatory (5 spp.), scavenger (5 spp.) and aquatic (4 spp.) species. Most results for individual species were similar to focal-animal studies and to other information in the literature. Members of the terrestrial guild were most often on the ground (58–78%). Predators and scavengers were most often in flight or perched (90–100% and 67–96%, respectively) but scavengers were more often standing on the ground (2–23%). Aquatic species were most often feeding or standing (49–65%). Predatory species were most often alone or in pairs, as were predatory members of other guilds (Sagittarius, Terathopius, Trigonoceps). Two terrestriol species were in small social groups (Struthio, Bucorvus), while scavengers and aquotic species were most often in larger groups. The proportion of immatures recorded within species was 3–35%. For seven dimorphic species, the sex ratio deviated from equality for the two social terrestrial species (Struthio, Bucorvus). Differences between species within guilds were often related to detailed differences in their ecology