Tyrosinase activity in relation to plumage color in weaver birds ( Steganura paradisaea)

Abstract

1. 1. In male weaver birds ( Steganura paradisaea) the nuptial plumage consists of black dorsal feathers with white breast and orange collar. The female is at all times grey-brown on the dorsal surface with white breast and is indistinguishable, w with respect to plumage color, from males when the latter are not in nuptial plumage. 2. 2. Measurements of tyrosinase in the skin from which feathers arise (feather tracts) were made in relation to sex and season. It was found that tyrosinase activity is low in feather tracts at all times, except that when the male enters nuptial plumage, the dorsal feather tracts show relatively high levels of this enzyme. 3. 3. In general, dorsal tracts show greater activity than ventral tracts; this difference is greatly accentuated in males entering nuptial plumage. 4. 4. Since the activity of feather tract tyrosinase appears to vary in accordance with gross changes in feather color, it is concluded that variations in the activity of this enzyme may play an important role in the hormonally regulated plumage cycles of male S. paradisaea.