38 THE MOLT. related species molt differently, but the manner and time of molting among individuals of the same species may vary according to their sex, age, and physical condition. At the close of the nesting season all birds renew their entire plumage by molting. The following spring, before the nesting season, most birds molt their body feathers, retaining those of the wing and tail. A few, however, like the Bobolink, have a complete molt at this season also. Others molt only a few of the body feathers, while some birds are adorned at this season with special nuptial plumes. The beautiful aigrette plumes of the Heron consti- tute a nuptial dress of this kind. It is for these plumes that the birds have been slaughtered in such enormous numbers that if the demand continues they will speedily become extinct. Some birds, whose fall plumage is edged with a dif- ferently colored tip to each feather, do not molt in the spring, but acquire their wedding dress by the slow wear- ing off of the fringes to the feathers which have dis- T October. Fig. 23, March. June. January. Feathers from back of Snowflake, showln.fr seasonal changes in form and color due to wearing off of tips. (Natural size.) them during the winter. The Snowflake, for instance, changes from brown and brownish white to pure black and white by losing the brown tips which have concealed the black or white bases of his feathers.
