Predation by free-roaming domestic cats on migratory and resident birds during spring passage in a southern Tunisian oasis

During migratory stopovers, migrant birds may face increased predation threats, particularly as they prioritize foraging to replenish energy reserves and resume migration quickly. Such predation risks are likely elevated in anthropized stopover sites because of increased activity of human-associated predators, notably domestic cats (Felis catus). In this study, we investigated the predatory impact of cats on birds during the spring stopover in a southern Tunisian palm oasis, an area known to attract migrants and where free-roaming cats are abundant. We monitored feather remains scattered on the ground as indicators of cat predation and investigated the temporal trend of bird mortality throughout the spring migration period. We also assessed whether trans-Saharan birds were more susceptible to predation by cats compared to resident birds, as would be expected if trans-Saharan birds showed reduced vigilance and/or poorer body condition compared to resident species. From a total of 121 feather piles recorded, we identified 20 bird species, including 13 migratory species that accounted for 44% of records. The highest rates of cat predation on birds were observed during the peak of migratory passage, coinciding with the period of highest bird abundance. During this period, the number of resident and trans-Saharan migratory birds killed by cats was proportional to the relative abundance of these bird groups. Overall, our study highlights the importance of recognizing free-roaming cats in North African oases as a potential threat to trans-Saharan migratory Palearctic birds. We advocate for sustained research and conservation efforts to be directed towards addressing this issue.