Abstract

The migratory strategy of the Garden Warbler Sylvia borin, a long-distance passerine migrant, has been the subject of many studies. Garden Warblers stop-over to refuel at suitable sites both in Europe and in sub-Saharan Africa as they migrate to their wintering grounds. This strategy therefore provides an excellent opportunity of understanding the movement and energetics of migratory birds in general. In this presentation we will present data from several sites along the migratory journey: Southeastern Sweden (Ottenby Bird Observatory 1950-2008), Northern Nigeria (Malamfatori near Lake Chad 1999-2000), Central Nigeria (Amurum near Jos 2001-2006) and Southeastern Nigeria (Becheve Nature Reserve, Obudu Plateau Oct-Dec 2005 and Dec 2007-Jan 2008). Garden Warblers start to migrate towards SW over Europe in July-August and start to arrive in Northern Nigeria from the end of August. After spending a short time in the Sahel zone, they move down to Central Nigeria in the Guinea savanna where conditions deteriorate in the north. At the Amurum site, they start to increase their body mass again in October-November and then, after being quite numerous, they disappear, probably migrating towards Southeast Nigeria and their final winter quarters. Garden Warblers begin to turn up in Southeastern Nigeria from mid-October and numbers gradually increase. The average fuel loads at the different sites vary markedly and probably reflect the migratory strategy and the distance of the next migratory leap. At Obudu the average fuel load was relatively lower as compared to the autumn mean at Amurum, suggesting that they may not embark on a longer journey further south. The highest fuel loads was found in spring at Amurum when birds are heading straight north over the migratory barrier imposed by the Sahara and most likely also the Mediterranean Sea. Very few Garden Warblers were trapped at Malamfatori in spring indicating that the Guinea savanna region serves as the departure point for the final trans-Saharan migration.