Carola Haas - US grants

Many migratory birds demonstrate a remarkable fidelity to breeding sites over a period of years. In some of these species, individuals that nested successfully in one year are more likely to return the following year than are individuals whose nests failed. It is not clear, however, whether this difference is due to increased dispersal or increased mortality among birds that fail. This study is an attempt to demonstrate experimentally a causal relationship between nest failure and dispersal. Three species of migratory birds breeding in shelterbelts in south- central North Dakota will be examined. The research is designed so that short-distance dispersal can be observed on the study area and so that comparisons can be made between return rates of birds with naturally successful, naturally failing, and experimentally failing nests. Understanding whether birds make dispersal decisions based on previous experience yields insights into the study of learning and long-term memory in animals. An accurate description of how birds choose their breeding territories and move between habitat patches is important for studies of gene flow, population structure and dynamics, evolutionary change in small populations, and individual response to changing conditions. The results of this study can also have practical applications in the field of conservation biology. Because this study examines birds breeding in isolated patches, it yields information on movements within and between small habitat "islands." Such information can be useful in the design and management of nature reserves.