A temperature-based monitoring of nest attendance patterns and disturbance effects during incubation by ground-nesting sandgrouse

Sandgrouse are birds of arid environments adapted to cope with extreme temperature variations. We used temperature data-loggers to remotely study incubation rhythms by pin-tailed and black-bellied sandgrouse in Spain. In both species, mates switched incubation roles twice a day, between 08:00 and 10:00 and between 19:30 and 21:30, when the nest and ambient temperature were most similar. During mate switches, sandgrouse preferred to risk a cooling rather than a warming of eggs. In the pin-tailed sandgrouse, the timing of morning switches was consistent within-pairs, while the timing of evening switches was more related to sunset time. Absences lasted longer following a disturbance than during a mate switch. During disturbances, changes in nest temperatures depended on the changes in outside temperature, and negatively correlated with absence duration. Absences following a disturbance were shorter when the outside temperature was higher. Nesting success was low (19%), with no noticeable effect of data-loggers. Our study highlights some of the constraints that birds breeding in arid environments, such as sandgrouse, face during incubation. It also stresses out the importance of evaluating the consequences of disturbances during incubation, in particular nest visits. Temperature data-loggers can provide an easy and effective way of monitoring nests, without the need of repeated nest visits.