Sometimes, the only option for a nest-box is a south-facing wall. In such cases, one needs to defend the nesting space from the sun. Experiments with a single double-skinned nest-box kept the temperature to 37°C on a day when the temperature reached 34°C in the shade. 40°C is thought to be the maximum safe limit. This cabinet has been installed on a house in Cambridge with a max-min thermometer inside for testing this summer. It has a double roof and the the front is an "air sandwich" made of 12mm marine ply. There are ventilation holes on the back with 12mm spacers to allow an air gap next to the wall. It is painted white to reflect the sun. The internal dimensions of each nest-box are roughly 400mm x 200mm x 175mm. The birds need to traverse an entrance (30mm x 75mm) through 36mm of plywood. During the summer of 2010, on a day when the temperature in the shade reached 29.1°C, the temperature in the box reached 30°C.
|