Associations of endemic Anas wyvilliana (Koloa Maoli or Hawaiian Duck) are non-random but not influenced by plumage or genetic relatedness

Abstract

Island endemic birds are under greater threat than their mainland counterparts. Restricted geographic ranges and historically reduced predation may affect island bird sociality, making such data important for conservation and management. However, detailed studies evaluating their sociality are uncommon. The federally endangered Anas wyvilliana (Koloa Maoli or Hawaiian Duck) is primarily threatened by hybridization with feral A. platyrhynchos (Mallard) and avian botulism outbreaks. Understanding A. wyvilliana social associations can shed light on preferences for or against A. platyrhynchos and hybrids and inform planned translocations. Microgeographic spatial genetic structuring where genetic relatedness scales with geographic distance is a potential liability for maintaining genetic diversity, and would particularly be detrimental during highly localized botulism outbreaks that could result in the removal of entire lineages. Using capture–mark–recapture and genetic data from the island of Kaua‘i, a stronghold of remaining A. wyvilliana, we constructed social networks and examined associations (inferred from trap co-occurrence) and spatial genetic structure. We found non-random social associations among adult and first-year A. wyvilliana, including evidence of preferential associations lasting longer than a month. These associations were not apparently influenced by plumage traits or body mass, suggesting a lack of social preference for A. platyrhynchos-like individuals. Importantly, we found no spatial patterns of relatedness within the species’ most heavily used site, Hanalei National Wildlife Refuge. Consequently, while botulism outbreaks remain a demographic threat, they are unlikely to remove correlated genetic diversity. Further, the lack of evidence of spatial genetic structure among both sexes and the presence of many unrelated conspecifics may enable A. wyvilliana to limit inbreeding and retain genetic diversity, even if sex-biased dispersal were to be limited. For future management, our results suggest that translocating A. wyvilliana captured in the same trap together will reduce the disruption of preferred social associations while also retaining genetic diversity among translocated individuals.