Effects of electromagnetic fields on body mass and food-intake of AmericanKestrels

Raptors commonly nest and roost on transmission towers and hydroelectric po les which exposes them to electromagnetic fields (EMFs) From power lines. O ur objective was to determine whether EMF exposure affected the body mass o f reproducing adult American Kestrels (Falco sparverius), and consequently, whether increased body mass was a function of increased dry matter intake related to EMF exposure. Captive kestrels were paired for one (short-term) or two (long-term) breeding seasons to determine EMF effects on body mass o f adults. Short- and long-term EMF exposure of males affected overall mean body mass during the reproductive season, with EMF males heavier than contr ols when molting began. In contrast, the body mass and pectoral muscle scor es of females were unaffected by EMF exposure during egg laying, 20 days po st-laying, and after 70 days of EMF exposure. There were no significant eff ects on body mass or food-intake of wintering kestrels related to 10 days o f EMF exposure. Our results can be explained by EMFs affecting the birds' r esponse to the photoperiod as indicated by altered melatonin levels in thes e male kestrels. The onset of molt was advanced in EMF male kestrels.