Vernal migratory behavior in captive white-crowned sparrows, Zonotrichia leucophrys

Abstract

Avian migration, the biannual movement of birds from non-breeding to breeding grounds, is a global phenomenon that has fascinated scientists for centuries. The presence of seasonal unrest in caged birds coincident with migration in free-living individuals led to the identification of migratory restlessness, or the expression of migration specific locomotor activity and behaviors characteristic of migration in captivity. This thesis establishes a paradigm for testing the expression of migratory restlessness in captive white-crowned sparrows (Zonotrichia leucophrys). First, given the role of circadian oscillators in regulating the expression of locomotor activity in other migrant species, as well as the effects of light cues on locomotor activity of migrants, I investigated the interplay of endogenous and exogenous input in the complete expression of migratory restlessness in Gambel's white-crowned sparrow (Z. 1. gambelii). Exposing birds to constant conditions of dim and bright light, I determined that expression of intense nocturnal activity is controlled by a circadian oscillator but expression of migration specific behaviors requires dim light conditions. Second, the resident race of white-crowned sparrow (Z. 1. nuttalli ) expresses some migratory activity. However, investigating the development of this activity from late fall to spring, I showed that patterns of locomotor activity are fundamentally different from the migratory congeners. While migration specific behaviors are present in a few individuals, nuttalli does not express complete migratory tendencies. Finally, considering speciation of the 3 Pacific races of Zonotrichia leucophrys, I tested the step-wise evolution of migration strategies from long-distance migrant to resident life history using previously established characteristics of captive migrants. I concluded that Z 1. gambelii, pugetensis and nuttalli express tendencies proportionate to the migratory distances covered. Thus the 3 races represent a spectrum of step-wise evolution from a long-distance migrant ancestor. In summary, my research has demonstrated that the complete expression of migratory restlessness in captive birds is a reliable measure for the analysis of multiple facets of avian migration.