Incubation routine of Saunders's Tern Sternula saundersi in a harsh environment

Abstract

Saunders's Tern (Sternula saundersi) is a small ground-nesting seabird which breeds in the coasts and islands of Africa and Asia bordering the northern Indian Ocean. Despite having a wide distribution, little information is available on the breeding biology of this species. This study was carried out on Farasan Islands, Saudi Arabia, to document some aspects of the breeding biology of this species using a small trail camera. Such camera systems can reveal the incubation routine of this species in such a harsh environment. The midday ground temperature in March may reach up to 50 °C, while the midnight ground temperature may only reach 20 °C, thus leaving the eggs unattended even for few minutes, especially during the hottest and coldest parts of the day, may cause nest failure. This huge variation in ground temperatures between day and night gave us an excellent opportunity to test the behavioural mechanism used by the parents for maintaining the optimal egg temperature so as to protect their eggs. We found that nest attendance increases when the temperatures deviated from the optimal egg temperature, and nests were incubated for more than 90% of the time during the hottest and coldest parts of the day to prevent eggs from harmful temperatures.