Most organisms occupy environments that vary in space and time. Environmental conditions often change rapidly, with little or no advance warning. Survival and reproduction depend on animals' ability to perceive these unpredictable events and to adjust physiology and behavior quickly and appropriately. The stress response is one mechanism by which animals can redirect behavior and physiology to cope with unpredictable events in the environment. When white-crowned sparrows return to their mountain breeding grounds each May, weather conditions are extremely unpredictable, and fresh snow can temporarily cover all available foraging areas. The birds' behavior can change rapidly and dramatically in response to these storms. They often abandon breeding territories and move temporarily to lower elevations (i.e., make facultative altitudinal migrations), where weather conditions are less severe and food is available. This proposal includes three kinds of studies. First, in a series of field studies the relationships between food availability, body condition, stress physiology and facultative altitudinal migration will be investigated. Second, in the laboratory, interactions between these factors (food availability, body condition, stress physiology and activity) will be tested under more controlled conditions. Third, reproductive success will be measured, permitting the evaluation of the functional relationships among the environment, physiology, and fitness. Broader impacts: This study will make several general contributions. It will provide research and training opportunities for several undergraduates and graduate students. The PIs place strong emphasis on undergraduate involvement in research, and this project will reflect that. Several aspects of this project (determination of changes in snow cover, food availability, territory quality, nest location and individual localization of birds using radiotelemetry) are ideal for undergraduate projects. The project also lends itself to involvement of undergraduates in laboratory studies; the birds are extremely tractable in captive studies. As an integrative, collaborative project, it will foster interactions among universities, and help to develop field-bridging approaches to the study of physiology and behavior. This study will also serve to maintain a long-term database on the breeding biology of this species, started by Martin L. Morton in 1968. With the continuing data on environmental conditions (snow depth, snow cover, temperature), body condition, and timing of reproduction, we can examine long-term trends in features of the population that may be affected by global climate change, such as overall population reproductive output or inter-year adult survivorship.
