Data loggers are very useful sensors, which allowed us to take measurements of Relative humidity and Temperature every half hour, during three months (June to September).
We installed 10: one in each face of both of our stocks, and two exterior ones (which serve as control).
Since we wanted to imitate the conditions of a burrow, we excavated a 5 cm wide hole, 70 cm deep into each stock face. Then we introduced a cylinder made out of mesh, so that if our hole collapsed, we would still be able to rescue the sensors. The material of the cylinder had to allow temperature and air exchange. Finally, we closed the entrance of the cylinders with more mesh, so that Sand Martins wouldn’t be able to get in.
The results of these sensors will be posted soon!