Molecular insights on re-colonization of the Limpopo Valley, South Africa, by Southern Ground Hornbills

Southern Ground-Hornbills (Bucorvus leadbeateri) are co-operative breeders that occur in groups of
2–9 individuals. Long life spans, large territory sizes
(100 km2
), and low reproductive rates render these birds
vulnerable to threats such as loss of habitat, persecution,
poisoning and loss of suitable nesting sites. In the Limpopo
Valley of South Africa, the species is currently re-establishing after a serious decline in numbers. In this study, we
use observation, capture and population genetics approaches to gain insights into the nature of the re-colonisation
of the Limpopo Valley. We determined the effective
population size, genetic diversity estimates, relatedness,
parentage, sex ratios, age structure and productivity. The
re-colonisation of the Limpopo Valley was shown to have
occurred by a number of unrelated individuals. This was
demonstrable by the very low levels of average relatedness
of the population, as well as the favourable levels of
heterozygosity across age and sex categories. Within-group
relatedness was as expected, with juveniles related to at
least one parent from their natal group. Inferences on
breeding behaviour based on genetic testing results provides the first evidence that SGH are not as monogamous
as previously thought, with two instances recorded of extra
pair copulations. Finally, we demonstrate the application of
microsatellite markers to enumerate processes that are
difficult to quantify through observation.