Effects of electromagnetic fields on the growth of nestling American Kestrels

We studied nestling American Kestrels (Falco sparverius) in a laboratory se tting to determine whether exposure to electromagnetic fields (EMFs) affect ed their growth. Captive nestlings were raised by their parents under contr ol or EMF conditions similar to those occurring near transmission lines in the wild. Nestlings also were exposed to EMFs as embryos when incubated by their parents. Measurements of body mass, and lengths of tarsi, antebrachia , and feathers were taken every three days after hatching. EMF exposure aff ected the growth of female and male nestlings. EMF nestlings and fledglings were heavier and had longer tarsi. The periods of maximal weight gain and antebrachial growth were delayed in EMF males compared to controls, althoug h EMF males were heavier and had similarly long antebrachia to controls by 21 days of age. Growth of ninth primaries and central rectrices of nestling s were unaffected by EMF exposure. Growth patterns of male and female kestr el nestlings were similar to those previously reported for this species, al though the periods of maximal weight gain and bone growth did not occur ear lier in EMF males than females as it did in controls.