Behavior of free-ranging and captive American kestrels under electromagnetic fields

Wild birds, particularly raptors, commonly use electrical transmission stru ctures for nesting, perching, hunting, and roosting. Consequently, birds ar e exposed to electromagnetic fields (EMFs). The amount of time that wild re producing American kestrels (Falco sparverius) were exposed to EMFs was det ermined, and the effects of EMFs on the behavior of captive reproducing kes trels were examined. Wild kestrels were exposed to EMFs for 25% to 75% of t he 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, capt ive kestrels were exposed to EMF levels experienced by wild kestrels nestin g under 735-kV power lines. Captive EMF females were more active, more aler t, 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 courts hip may be linked to changes in corticosterone, but likely not melatonin. O bserved behavioral changes were unlikely to directly result in the better g rowth of nestlings and fledging success, or poorer hatching success, of the EMF group, as previously reported. Behavioral changes of captive EMF kestr els may be observed in wild kestrels.