Utility of a small temperature logger to monitor the breeding phenology at nest boxes of passerine bird species

We tested a temperature logger for monitoring the breeding schedule of cavity nesting birds, and concluded that they provided accurate and valuable data with which to deduce nesting activity. The temperature sensors were attached to the bottoms of the nest boxes for Ryukyu Robins Erithacus komadori, Varied Tits Parus varius, Great Tits P. major, and Red-cheeked Starlings Sturnus philippensis. The temperature data within the nest boxes were compared with ambient air temperatures. From changes in the temperature difference between the internal nest box temperature and the ambient air temperature (nest box - air temperature) we could deduce the start of incubation, hatching, and fledging for Varied Tits, Great Tits, and Red-cheeked Starlings. We could deduce those periods for Robin nests if we attached the sensor 1.2cm above the bottom. Therefore, specially designed attachment methods are needed for some species. These trial studies confirm that research on reproductive ecology can be enhanced by use of a temperature sensor and data logger when studying cavity nesting birds.