Power lines rewire avian hormone

Science News, Nov 20, 1999 by J.R.

Birds roosting along high-power electric-transmission lines may get more than a lofty perch. A new study suggests they may also undergo a shift in biochemical signals controlled by melatonin, the nighttime hormone that sets their biological clocks.

Kimberly J. Fernie of McGill University in Quebec City observed that several conservation groups had begun providing platforms on transmission-line towers for roosting raptors. She and her colleagues duplicated the conditions on the platforms by exposing captured American kestrels to electromagnetic fields (EMFs) of 30 microteslas throughout two breeding seasons.

Ordinarily, the concentrations of melatonin in males' blood drop gradually during the roughly 70-day breeding season. However, a decline that normally takes 10 weeks in unexposed males happened in 6 weeks in the EMF-exposed birds, Fernie reports. Although adult females appeared unaffected by the fields, fledglings of pairs that had roosted for two breeding seasons in the EMFs also produced less melatonin than normal, her team reports in the November ENVIRONMENTAL HEALTH PERSPECTIVES.

Fernie says her findings suggest that "the birds might be responding to the EMFs as if they were light." Although the degree of melatonin suppression was only moderate, she would like to investigate whether it's shifting the birds' calendar in ways that might affect migration or other seasonal changes.