Spring migration phenology of trans-Saharan migratory birds at a southern Tunisian oasis

North African date palm oases are regarded as important stopover sites for trans-Saharan migratory birds after their Sahara crossing during spring migration. However, little is known about the timing of migration through these areas. In this study, we investigated the spring migration phenology of trans-Saharan birds in a southern Tunisian oasis. Using daily bird captures spanning the entire spring season across two non-consecutive years, we determined the start, peak and end dates of migratory passage for 18 trans-Saharan passerine species. We found that the spring migratory passage through this area (Kettana oasis) extended from late March to late May, with migration windows spanning 3-6 weeks depending on the species. The start, peak and end dates of migratory passage were negatively correlated with wintering latitude, indicating that species wintering in the Sahel passed earlier than those wintering farther south, and highlighting an effect of migration distance on passage timing. For three species (the Eurasian Golden Oriole Oriolus oriolus, Common Whitethroat Curruca communis, and Tree Pipit Anthus trivialis), captured individuals were marked, and their sex was determined genetically using blood samples. Results suggested that the Eurasian Golden Oriole is transient, as there was a low recapture rate (one individual recaptured out of 147 marked). However, individuals of the Tree Pipit and Common Whitethroat, two species with relatively wide migration windows (>30 days), had minimum stopover durations of up to 7 and 10 days, respectively. For these two species, males tended to migrate earlier than females, supporting the protandry hypothesis, although there was no significant difference in minimum stopover duration between the sexes. Overall, our findings provide new insights into the spring migration patterns of trans-Saharan birds across southern Tunisia, emphasising the significance of this stopover area for these species.

Museo Nacional de Ciencias Naturales
Universite de Gabes