Breeding Biology of a Globally Significant Population of African Openbills (Anastomus lamelligerus) in Zambia

Population data on the African Openbill (Anastomus lamelligerus, hereafter Openbill) are largely lacking. We surveyed Openbill colonies on the Barotse Floodplain of the Zambezi River in western Zambia, describing nest site characteristics, clutch size, and brood sex ratios. We also monitored the movements of a male with the first telemetry transmitter deployed on the species. He travelled an average of 16.4 ± 9.6 (SD) km roundtrip during 73 foraging trips from its nesting colony. In July 2023, we surveyed colonies and estimated nest abundance from the air, identifying three large colonies in dense Phragmites spp. reedbeds along the Zambezi River channel. There were approximately 70,000 Openbill nests in the three colonies combined, with the largest colony estimated to have 57,884 nests. This colony also had 546 African Spoonbill (Platalea alba) nests, making it the largest known Openbill and African Spoonbill breeding site in Africa and one of the world's largest known long-legged wading bird nesting sites. Our study provides a snapshot of a globally significant Openbill population but also shows that much more research is needed.