During the past four winters an effort has been made to devise a satisfactory method of estimating the percent of young among the whistling swan population wintering in the Chesapeake Bay. Work to date indicates that this can be done by use of well distributed 35-mm. aerial color slides. Combining photography with direct visual appraisal was tried in the winter of 1965. The tentative conclusion from this was that use of aerial photos for large, densely packed flocks and visual appraisal for widely dispersed flocks would give accurate results at somewhat less expense than using the photographic method exclusively. In addition to percent young, average brood and family size can also be determined by these methods. It was also noted that the percent of "gray" birds observed decreases steadily throughout the winter. Data from the 1964 breeding season indicate that cygnets from the western areas have a higher mortality rate than those from eastern areas.
