Does the desert adapted Grey Falcon rely on food for water more than its congeners?

Abstract

To understand the various adaptations of endothermic desert adapted species to their hot arid environment it is crucial to understand their drinking habits. Birds of prey, including the species of the genus Falco, are said to be able to survive without drinking even in hot arid environments, and acquire the water they require (for evaporative cooling, for example) through their food. The Grey Falcon (Falco hypoleucos), a rare Australian endemic, stands out among its congeners in that its entire population is absolutely restricted to a hot arid environment. These birds have fewer and less reliable surface water sources than congeners in more mesic environments. Surprisingly, we have only two observations of Grey Falcons drinking in the wild. We describe these here, the first such records, and relate them to the extended periods spent observing these birds. We propose that water intake through food plays a greater role in the biology of the desert adapted Grey Falcon than in any other species of the genus Falco. Further investigations into the dependency of the Grey Falcon on food for its water will help to understand the complex interplay of physical, physiological, behavioural and environmental characteristics that allow these and other animals to persist in extreme desert environments. The issue appears relevant to many desert-living animal species because frequency and severity of weather extremes are predicted to increase under a changing climate.