A genetic and stable isotope interpretation of behaviour and social structure in Pale-winged Starling Onychognathus nabouroup

Abstract

Starlings have received much attention in the field of vocalisation and the link between song and social structure. The aim of the present study was to use the microsatellite markers developed in this study alongside carbon and nitrogen isotope ratios (δ13C and δ15N) to understand the population structure and social structure in Pale-winged Starlings (Onychognathus nabouroup), songbirds found in southern Africa. Using next-generation sequencing, 48 microsatellite markers specific to the Pale-winged Starling were isolated and developed. A total of 77 birds were sampled from the Augrabies Falls Nature Reserve in South Africa (n=53) and the Ai Ais-Richtersveld Transfrontier Park in Namibia (n=24), respectively and genotyped using fifteen polymorphic microsatellites. STRUCTURE analysis revealed a lack of genetic structure and low genetic variation between the two populations. Each population has a high degree of genetic diversity present between individuals. Movement of individuals between the two populations appear frequently and maintains gene flow between them. Stable carbon and nitrogen isotope ratios (δ13C and δ15N) in feathers revealed a clear distinction between the two populations of Pale-winged Starlings sampled from the Augrabies Falls Nature Reserve and the Ai Ais-Richtersveld Transfrontier Park. Male Pale-winged Starlings are larger than females and were found to occupy higher trophic levels than females in samples from both the populations. Based on differences in male and female physiology we can propose that males have access to food of higher trophic levels because of their size. Individual foraging specialisation within each population is also apparent. Regardless of genetic relationships these birds maintain a stable social environment and harbour strong social bonds between same and opposite sex group members as well as mates