Drinking and bathing behaviour of raptors in an arid, warm environment: Insights from a long-term camera trapping study in Namibia

Raptors are thought to obtain much of their water from their food as pre-formed and metabolic water, and therefore not by drinking. However, there are few publications about their behaviour at waterholes to test this idea. This study analysed 6 291 camera trap observations of raptors over 11 years at waterholes in a game reserve located in the warm, arid environment of north-central Namibia. Of 45 species recorded in the area, 12 were never recorded at water, whereas another 13 species were recorded 100 or more times at water. While there, raptors spent most time drinking, standing in the water, or bathing. Diurnal raptors usually visited water in the middle – and heat – of the day while owls were present throughout the night. Most visits to water were between May and November which were the driest months of the year. We found a strong inverse correlation (p < 0.0001) between the number of visits and the relative humidity in that month, suggesting that water balance is an important factor driving this behaviour. In general, these findings indicate that many raptors make much greater and seasonally changing use of water than is commonly assumed and appear to do so to help meet their physiological needs for water and thermoregulation. Many other raptors, for example most falcons and kestrels, however, have little or no need for drinking or bathing, begging answers to questions about why and how these differences and variations exist. This study also raises questions about how raptors that visit water frequently will respond to increasing heat and aridity.