Thermoregulation of Budgerigars Exposed to Microwaves (2.45 GHz, CW) during Flight

Abstract

Budgerigars (Melopsittacus undulatus) flying at 37 km h⁻¹ in a wind tunnel were exposed to 2.45 GHz continuous wave (CW) radiation at power densities of 50 and 0 (control) mW cm⁻² for 600 s. Body temperatures were measured before and after flights, and thermoregulatory behavior was observed during and after flights. A power density of 50 mW cm⁻² induced thermoregulatory behaviors at ambient temperatures ( $T_{a}$ ) above 26 C. Budgerigars were forced to land before the end of the 600-s exposure period when $T_{a}$ was greater than 32 C. The specific absorption rate (W kg⁻¹ mW⁻¹ cm⁻²) of small bird species (<40 g) is greater than that for larger species and is more sensitive to the orientation of the long axis of the body to the electric (E) vector of the microwave field. Small bird species may be less susceptible to microwave-induced hyperthermia due to a greater ability to lose heat by convection, reradiation, and evaporation of water.