The habitat use and energetics of American black ducks (Anas rubripes) wintering at Chincoteague National Wildlife Refuge, Virginia, were investigated. Twenty-two female black ducks were systematically radiotracked on the 25,600 ha study area between 15 December 1985 and 28 February 1986. Diurnal time and energy budgets were constructed by distributing 1,471 scans (collected in 1985-86 and 1986-87) over a time-tide matrix within refuge, saltmarsh, and tidal water habitats. Sixty-four ducks were collected during early, mid, and late winter in 1985-86 to determine changes in carcass composition. The Habitat Suitability Index (HSI) model for wintering black ducks was evaluated. Age affected range and core areas but did not affect habitat selection. Tide, ice, and time of day affected habitat use. Refuge pools were used during the day and saltmarsh was used at night. Subtidal water was used during periods of icing. Black ducks fed least and rested most when in refuge pools but fed most and rested least when in tidal waters. Black ducks curtailed feeding and increased time spent in alert and locomotion behaviors in response to disturbance. Whole carcass analysis indicated that black ducks were at least as fat and heavy in the spring as they were in the fall. Comparisons with similar work in Maine suggested that black ducks wintering in Maine and Virginia expend the same energy at a given temperature. However, because of lower temperatures, black ducks collected at Chincoteague were in relatively better condition than ducks wintering in Maine. / Master of Science

The vegetation characteristic of the Back Bay area is largely Austroripariam. On the Back Bay National Wildlife Refuge about 330 species and varieties of 198 genera from 76 families were found. Of these plants, five are important submerged aquatic water-fowl foods and twenty-four are emergent or marsh food species. The present production of submerged waterfowl food plants is much below the potential for the area, though somewhat greater than in past years. The factor now most responsible for this limited growth is turbidity of the water. The chief cause of turbidity is wave action due to wind. The action of carp is a secondary cause. In the view of the extreme difficulties and expenses of controlling turbidity, no management practices can be recommended for increasing the growth of submerged aquatics other than continued prevention of pollution and maintenance of as low a carp population as possible. Marsh management, on the other hand, is thought to offer good possibilities for benefitting waterfowl conditions on the area. Therefore, it is believed that any management efforts to improve waterfowl food plant conditions on Back Bay can be more profitably applied to marsh and emergent species than to submerged aquatic species. / M.S.