Departure of terns in spring 1999 from Namibia
Atlantic seabirds , Volume 5 - Issue 3 p. 111- 118
During a study of terns wintering along the Namibian coast in February-April 1999, departing terns were recorded. Most terns departed in the evening when other terns went to roosts. Departing flocks consisted only of Sandwich Sterna sandvicensis, Common S. hirundo and White-winged Black Chlidonias leucopterus Terns, of which the first two species originate from north-western European breeding grounds. A major drop in roosting numbers occurred from late February onwards and also a decline in body mass of Common and Sandwich Terns was noted during this period, while departure was observed from early March onwards. Even though the observational data are anecdotal, they suggest that the three tern species migrate not only at night, but also that they may well cross at least part of their route in a straight line. The dominant tern migration strategy remains obscure, but time constraints seem an unlikely cause of jump migration. The jump migration strategy might indicate that the number of suitable stop-over sites is limited.
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