Human-facilitated feeding on Date Palm Phoenix dactylifera sap by trans-Saharan warblers during spring stopover in a Tunisian oasis

Capsule: Some trans-Saharan warbler species feed on human-extracted Date Palm Phoenix dactylifera sap during spring migratory stopoverAims: To investigate the behaviour of birds feeding on Date Palm sap at a Tunisian oasis during the spring migration season.Methods: Birds feeding on Date Palm sap were monitored during the peak of spring migratory passage of trans-Saharan birds in southern Tunisia by recording the species involved and their numbers, and noting whether there were agonistic interactions between them. Data were used to describe the assemblages of birds feeding on Date Palm sap.Results: We recorded five trans-Saharan warbler species feeding on Date Palm sap, either in single- or mixed-species flocks. Aggressive conflicts were common, suggesting competition by interference within this bird assemblage. However, other abundant fruit-eating trans-Saharan warbler species were never seen feeding on Date Palm sap, possibly due to the potential inability to assimilate some of its components, or simply because they did not need to ingest it for reasons related to their migration strategy.Conclusions: Our findings reveal that Date Palm sap is a food resource for some trans-Saharan warbler species, highlighting a rarely documented human-facilitated feeding behaviour in birds. They also underline the high ecological plasticity of these warbler species, capable of using different food resources to meet the needs of their challenging migratory journey.