A pulse-position-modulated multichannel radio telemetry system for the study of the avian nest microclimate

A multichannel biotelemetry system using pulse position modulation has been developed to monitor continuously the environment in birds' nests. Probes to measure temperature at six points, relative humidity, light and egg attitude, together with a transmitter and power supply are contained in a fibreglass shell, having the shape, size and weight of the egg of the species being studied. The sensing egg is placed in the nest at the completion of a clutch and not removed until the young have hatched. A low-power transponder is used to relay the signals up to 2 miles to a data-logging system in the laboratoy.