Importance of Topography in the Selection of Drinking Sites by Sandgrouse

Undulating ground resembles cover in offering opportunities for vertebrate predators to remain hidden from prey and vice versa. Some species prefer to forage in the open so as to avoid being surprised by predators while others remain close to cover and use it as a refuge when attacked. To determine if topography was important in influencing the sites chosen by sandgrouse for drinking, we measured a range of variables at water-holes used by blackbellied, pin-tailed and crowned sandgrouse (Pterocles orientalis, P. alchata and P. coronatus) in Spain and Israel. All species drank at sites reasonably close to their feeding and nesting areas. In Spain, water-hole selection was quantified using stepwise logistic and linear regression analysis. The amount of dead ground surrounding each water-hole (i.e. ground not visible to drinking sandgrouse) was the most important factor influencing the birds' choice. These regression relationships were used to predict the pattern of use of water-holes at two localities in Israel. The agreement between observed and expected levels of exploitation was good, confirming the strong aversive influence of dead ground. Predatory birds were the biggest source of disturbance at drinking sites. By choosing sites with the least dead ground, sandgrouse probably reduced their risk of being surprised by predators while drinking.