Pterylosis and Molt in Cassin's Finch

Abstract

Migratory birds which breed in the strongly seasonal high montane environment of middle and high latitudes must carefully integrate their limited time and energy to successfully reproduce, molt, and prepare for fall migration while environmental conditions are favorable. Generally these events are temporally segregated on the breeding area although some populations, including Carpodacus e. erythrinus, delay the postnuptial molt until arrival on the winter area (Stresemann and Stresemann 1966), thereby separating these energy-demanding processes. The nomadism of Cassin's Finch (Carpodacus cassinii) and inaccessibility of montane breeding populations to investigators presumably have precluded intensive field studies of this species. The few details known are from observations by resident naturalists or by those engaged in faunistic surveys (Ridgway 1877, Henshaw 1879, Grinnell 1908, Taylor 1912, Bailey 1928 and others). From the summer of 1971 through early summer 1974, I studied Cassin's Finches in an environment