The status and distribution of three species of Sternula terns on the eastern coast of Africa and in the western Indian Ocean, with two species new for Mozambique

Abstract

The status of three Sternula terns in southern and eastern Africa and the Indian Ocean is updated based on observations in Mozambique during October 2009–August 2021. Damara Tern S. balaenarum and Saunders's Tern S. saundersi, both new to Mozambique, were found at the San Sebastian Peninsula in August 2018 and have been recorded regularly since. Damara Tern arrived in May, numbers were lower June–July, with a peak of 100+ in August–October. Breeding plumage was assumed by late October and all departed in early November; those aged were all adults. Observations of ringed birds suggested they originated from colonies in South Africa. Numbers of Damara Tern reached the Key Biodiversity Area designation threshold population for the site in 2020. These are the first records of large numbers of Damara Tern in the Indian Ocean, whilst timings suggest the species is partly transient at the site and may also occur further north. Saunders's Tern was recorded at San Sebastian in all months except March and April, with 5–80 regularly present, and peak numbers perhaps in October–December. Birds were observed in a range of plumages in all months, from non-breeding, transitional to full breeding. Courtship feeding was observed in September–November suggesting at least some attempt to breed locally, although disturbance is high. Birds in non-breeding plumage may stem from Northern Hemisphere breeding localities. Little Tern S. albifrons was a numerous migrant in southern Mozambique in October–May, peaking in April when large numbers were observed during pelagic trips to the continental shelf edge, and at onshore roost sites including San Sebastian. Smaller numbers fed in coastal lagoons and freshwater lakes. Three Little Terns had been colour-ringed in Israel.