THERMAL EFFECTS OF SHORT RADIO-WAVES ON MIGRATING BIRDS

Shortwave broadcast stations emit electromagnetic radiation and may th us affect organisms in their vicinity. On the basis of the design of a planned Voice of America station in the Arava Valley, Israel, and the station's broadcast specifications, we examined its potential as a ha zard to migratory and resident birds, We built a computer model to est imate the thermal effects of the station's projected radio-frequency ( RF) radiation on birds within its radiation canopy during horizontal f lapping flight, during takeoff, and at rest. Our model indicated that small- to medium-sized birds would not be in thermal danger during fli ght through the station's RF radiation canopy. Large birds that take o ff through the station's radiation canopy might incur an increase in t heir total heat load. Yet, even were no thermoregulatory mechanisms av ailable, the possible rise in body temperature would be within the bir d's sustainable range. With heat dissipation mechanisms available, and as long as the body surface:air temperature gradient remained in the bird's favor, even the largest bird would be able to contend with the heat increment imposed during takeoff through the radiation canopy. La rge birds landing on antenna structures might become vulnerable to ove rheating, but it is likely that these birds would depart rather than r emain where they are uncomfortably hot. Our approach can be generalize d to assess the impacts of shortwave radio stations on wildlife in the ir surroundings.