Effects of dietary fluoride on reproduction in eastern screech-owls

Sixty-six eastern screech-owls (Otus asio) were paired and randomly assigned to dietary treatment groups of 0, 40, or 200 ppm (mg/kg) fluoride (as sodium fluoride) in November 1981. Hatching success was adversely affected at the 200 ppm (mg/kg) level, suggesting potential detrimental impacts to wild populations exposed to fluoride pollution. Eggshell thickness was unaffected. Although fluoride concentrations were elevated in bone and eggshells, large variations among individuals were observed as well as a trend for eggshell residues to increase with sequence of laying. Females had higher residues of fluoride in bone than males. Although fluoride levels in bone and eggshells are useful indicators of exposure, the variability in residues among individuals makes residue data from field collections of limited usefulness in assessing hazards in wild birds.