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

ABSTRACTCapsule Some trans-Saharan warbler species feed on human-extracted Date Palm Phoenix dactylifera sap during spring migratory stopover.Aims 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. AcknowledgementsThe authors thank the farmers and palm tappers in Kettana Oasis for their kind support during the fieldwork. The authors also thank all members of the Ecology of Terrestrial Fauna research unit for valuable discussions on this work. Comments provided by the Editor and an anonymous reviewer greatly improved the manuscript and were much appreciated. This study complies with the current laws of Tunisia. Permits were obtained from the Forest Service of the Tunisian Ministry of Agriculture (permit reference: 437-07/02/2022).Disclosure statementNo potential conflict of interest was reported by the authors.Additional informationFundingThis study was funded by the Spanish National Research Council (CSIC), project COOPA20475, and was part of the activities of the ‘Ecology of Terrestrial Fauna’ research unit, supported by the Tunisian Ministry of Higher Education and Scientific Research.