Large nocturnal roosting aggregations and mass movements of Whiskered Terns in Liuwa Plain National Park, Zambia

Abstract

The Whiskered Tern (Chlidonias hybrida) is little studied in southern Africa. In Zambia, it is primarily found in the south and west of the country, where the Barotse Floodplain and Kafue Flats are known to contain substantial numbers of terns. Although the species is common in Liuwa Plain National Park, there are no high counts. While in Liuwa in July 2021, we observed over 1,600 Whiskered Terns at a nocturnal roost, which was located on floating vegetation in the middle of a pan. In June 2022 we observed three large nocturnal roosts ranging from 400–725 terns as well as large early morning movements of as many as 850 terns dispersing towards floodplains outside Liuwa. Our observation in 2021 represents one of the highest concentrations of Whiskered Terns recorded in southern Africa and those in 2022 suggest terns may commute tens of kilometers to forage during the day but return to Liuwa to roost communally.