Water visitation patterns by Eleonora’s falcon at its breeding grounds: a case study using visual observations and camera traps

Abstract

Water is a vital resource providing multiple services to many organisms, including birds. Eleonora’s falcon is an iconic, long-distance migrant bird of the Palearctic region. While various aspects of its life history have been thoroughly studied, its dependence on water sources has been poorly documented. In this study, we examine for the first time the species’ visitation patterns at a complex of small, natural ponds of karstic water on a Greek island and provide a detailed description of its bathing and drinking behaviour using visual observations and camera traps. Our results indicate that the species visits the ponds systematically from spring until autumn to bathe and drink. Water visitation patterns suggest communal behaviour, most probably benefitting from increased vigilance in greater numbers. In spring, male falcons prevail during water sessions and the reverse pattern is observed in autumn, whereas morph ratio remains stable, close to the expected 3:1 ratio. Temperature, affecting the falcons’ foraging activity and/or their heat dissipation requirements, together with seasonal differences in labour division between sexes can explain a significant amount of the observed variability in water visitation patterns. Freshwater sources in most islets hosting breeding colonies are scarce, thus natural ponds in nearby larger islands are an important resource many falcons could rely on while at their breeding grounds. The identification and preservation of bathing and drinking spots where falcons gather in numbers across its breeding range is thus highly recommended. Considering the forecasted impact of climate change on karstic water we also encourage an in-depth analysis of the role of water in the adaptation of Eleonora’s falcon to a life in insular environments experiencing global warming. Last but not least, further investigation of the species’ communal behaviour regarding water use can also offer interesting insights in the species’ natural history. HIGHLIGHTS•Eleonora’s falcons visit the water ponds systematically and communally to bathe and drink •Temperature variability and differences in labour division between sexes explain water visitation patterns to a large extent