Productivity of the declining Bearded Vulture Gypaetus barbatus population in southern Africa

Abstract

Recent research has shown that anthropogenic influences are driving the abandonment of breeding territories in the declining southern African Bearded Vulture Gypaetus barbatus meridionalis population. Survival rates appear to be low (86% for adults) due to poisoning and collisions with powerlines, which are the primary causes of death from tracked birds. However, there is no information published on the population’s current productivity levels, and whether this may be a contributing factor in the declines of this population. This information is vital for a more holistic approach to the conservation of the population. In this study we use data from breeding territory surveys between 2000 and 2016 to estimate productivity for this population. Only around 54% ± 74% (17–91%) of pairs attempted to breed each year, and although nesting success for pairs attempting to breed was relatively high (0.75 ± 0.22; 0.44–1.00), this resulted in low productivity of only 0.42 ± 0.65 (0.28–0.67) young per pair per year. These results contrast with previous surveys, suggesting the productivity may have declined over the last three decades, principally due to many pairs not attempting to breed in each year. Understanding the factors influencing productivity amongst pairs could be useful to guide conservation actions.

Keywords: breeding rate, conservation, nesting success, population decline, productivity