The Role of Thyroxine on the Production of Plumage in the American Kestrel (Falco Sparterius)

Abstract

In a prior study (Quinn et al. 2002), we examined the effects of Aroclor 1242 (a mixture of polychlorinated biphenyls [PCB]) on feather production in the American Kestrel (Falco sparverius). The development of plumage is heavily influenced by the action and tinting of thyroid hormones (Owens and Short 1995, Kuenzel 2003). Although Aroclor 1242 was shown to cause decreases in plasma thyroxine (Quinn et al. 2002), no significant differences were observed in feather production or appearance between PCB and control treatments. The data presented here illustrate the relative roles of thyroxine on molt and plumage pigmentation in the American Kestrel.