Effects of perchlorate on growth and behavior of a granivorous passerine, the Zebra finch (Taeniopygia guttata)

Perchlorate (ClO4-) is a thyroid hormone inhibitor and persistent environmental contaminant that has been shown to impair thyroid function and growth in ground-dwelling birds. In this study, we used the zebra finch (Taeniopygia guttata) as a model to examine the effects of environmentally relevant perchlorate concentrations on growth and behavior of a granivorous passerine. On post-hatch days (PHDs) 3-14, finch chicks were orally dosed once per day with either 0, 10, 100, or 1000 mu g sodium perchlorate/g body mass, and multiple endpoints of growth and behavior were examined in birds up to 72 days of age. Mean (+/- SE) body mass and tibiotarsal length were significantly reduced in the 100 and 1000 mu g/g dose groups from PHDs 3-14, and this reduction persisted until PHD 40. Mean liver mass (PHD 15) in the 100 and 1000 mu g/g dose groups were significantly greater than controls. Mean brain mass and mean nuclear volume of the song control nucleus area X in brains of 72-day-old males did not differ among dose groups. All endpoints of finch behavior were significantly influenced by perchlorate exposure at the highest dose level. Compared to controls, birds in this dose group exhibited a greater begging intensity, decreased motivation for spontaneous movement (e.g., attempts to fly), and reduced capacity to wean themselves from parental care. On PHD 15, flight attempts were also significantly reduced in the 10 and 100 mu g/g dose groups, and the proportion of perchlorate-dosed birds attempting flight was less than half that in the control group. This study demonstrates a dose-dependent alteration of multiple growth and behavioral endpoints in zebra finches exposed to environmentally relevant concentrations of perchlorate. Comparable exposures in the wild may also affect normal development and behavior in similarly sensitive avian granivores.