The Annual Cycle of Plasma irLH and Steroid Hormones in Feral Populations of the White-crowned Sparrow, Zonotrichia leucophrys gambelii

Abstract

Plasma levels of immunoreactive luteinizing hormone (irLH) and 5 steroid hormones have been measured through the course of the winter breeding season and vernal and autumnal migration in both sexes of the White-crowned Sparrow, Zonotrichia leucophrys gambelii. Birds were captured in mist nets or traps on wintering grounds in Washington and California and on the breeding area in the vicinity of Fairbanks, Alaska. Blood samples were collected from a wing vein as soon after capture as possible. Birds were then individually marked with a unique combination of 1 or 2 colored leg bands for identification in field observations and laparotomy performed to assess the reproductive state. After sampling, all birds were released for subsequent observation and recapture.