Territoriality in the Willow Warbler Phylloscopus trochilus in its winter quarter in Lesotho

Territorial behaviour of the Willow Warbler Phylloscopus trochilus was studied in an urbanised habitat in Lesotho, southern Africa, in three consecutive wintering seasons (November–March 1999–2002). Contrary to expectation, the Willow Warblers were holding territories. As many as 34% of all territories were held permanently throughout the wintering season, and 33% were located at the same site for the three consecutive years. The intensity of territoriality (singing) tended to increase as spring migration was approaching (February–March). This was assumed to be a response to an increasing need to defend food resources required for fat deposition before departure. The birds showed a strong preference for feeding in Salix babylonica and Acacia dealbata.