Behavior of Free-Ranging and Captive American Kestrels Under Electromagnetic Fields

Abstract

Wild birds, particularly raptors, commonly use electrical transmission structures for nesting, perching, hunting, and roosting. Consequently, birds are exposed to electromagnetic fields (EMFs). The amount of time that wild reproducing American kestrels (Falco sparverius) were exposed to EMFs was determined, and the effects of EMFs on the behavior of captive reproducing kestrels were examined. Wild kestrels were exposed to EMFs for 25% to 75% of the observed time. On a 24-h basis, estimated EMF exposure of wild kestrels ranged from 71% during courtship, to 90% during incubation, similar to that experienced by captive kestrels (88% of a 24-h period). Additionally, captive kestrels were exposed to EMF levels experienced by wild kestrels nesting under 735-kV power lines. Captive EMF females were more active, more alert, and perched on the pen roof more frequently than control females during courtship. EMF females preened and rested less often during brood rearing. EMF male kestrels were more active than control males during courtship, and more alert during incubation. Increased activity of kestrels during courtship may be linked to changes in corticosterone, but likely not melatonin. Observed behavioral changes were unlikely to directly result in the better growth of nestlings and fledging success, or poorer hatching success, of the EMF group, as previously reported. Behavioral changes of captive EMF kestrels may be observed in wild kestrels.

Clutch size and egg volume in great tits (Parus major) increase under low intensity electromagnetic fields: A long-term field study

“…A behavioural study with captive American kestrels reported that birds were more active and alert just prior to egg laying under EMF exposure (Fernie et al, 2000b). This increase in locomotor activity was hypothetically attributed to EMF-induced changes in corticosterone titres (Fernie et al, 2000b). Experimental administration of corticosterone increased egg size in Uta stansburiana lizards (Sinervo and DeNardo, 1996), suggesting a potential link between EMF exposure and the increase in egg size observed in our study.…”

“…The answer will probably be found when looking at the physiological systems responsible for egg formation (Fernie and Reynolds, 2005). A behavioural study with captive American kestrels reported that birds were more active and alert just prior to egg laying under EMF exposure (Fernie et al, 2000b). This increase in locomotor activity was hypothetically attributed to EMF-induced changes in corticosterone titres (Fernie et al, 2000b).…”

“…Besides, all these studies were carried out in aviaries, with kestrels raised in captivity under ad libitum food conditions. Fernie et al (2000b) also estimated that free-ranging American kestrels breeding in nest-boxes ca. 1 m below 735 kV power lines in Canada were exposed to EMFs for 71% of the daytime during courtship and for 90% during incubation, thus suggesting that EMFinduced changes detected in captive kestrels may be observed in wild kestrels as well.…”