Many aspects of migration have been studied extensively, but little is known of how environmental conditions influence the behaviors displayed by migrants. Field studies suggest that such environmental factors as atmospheric conditions, nocturnal illumination, and food availability can affect migratory activity. We used 24 hr locomotor activity records and specific behaviors displayed by captive migrants to determine how nocturnal illumination and food restriction altered the migratory behavior of Gambel's White-crowned Sparrows (Zonotrichia leucophrys gambelii). Our results indicated that nocturnal locomotor activity was enhanced with increased nocturnal illumination at the source from 0 to 9 lux, even though the intensity of illumination that reached the birds remained <1 lux. Food deprivation had little effect on migratory restlessness per se, but resulted in increased locomotor activity during daylight hours and behaviors associated with attempts to escape from the cage. Thus, we suggest that migrants respond to variations in environmental conditions by altering both day and nighttime behaviors. Plasticity of behavior would allow free-living migrants to respond quickly to changes in the environment, thus enhancing the likelihood of successfully reaching their destinations.