Hormonal Induction of Feather Pigmentation in Ptarmigan

The study investigates the hormonal induction of feather pigmentation in ptarmigan species, focusing on the effects of various hormones on feather color changes. In Willow Ptarmigan, injections of posterior pituitary extract, MSH, LH, or FSH (effective only in females) led to pigmented feathers in plucked areas, while control birds grew white feathers. Similarly, White-tailed Ptarmigan implanted with hormone-cholesterol mixtures, including MSH, TSH, thyroxine, and an FSH/LH mixture, developed pigmented feathers, unlike controls that grew white feathers. The research suggests that MSH, gonadotrophins, and testosterone in males are involved in the natural control of plumage color. Previous studies indicated that daylength and ambient temperature influence molting and feather pigmentation, with hormones likely mediating these effects. The role of the thyroid and testosterone in plumage changes was also explored, highlighting the complex hormonal regulation of seasonal feather pigmentation in ptarmigans.