The bufflehead has traditionally been an invertebrate feeder 
although vegetation has formed a more important part of its diet 
in the past than it does now. During the 1970s the predominant 
food eaten by buffleheads was the duck clam (Mulinia lateralis) 
(Munro and Perry 1981). 
Ruddv Duck 
The ruddy duck (Oxyura jamaicensis) has shown a significant 
decline in numbers in the Chesapeake Bay during years of aerial 
surveys (Table 1; Fig. 8). Peak numbers occurred in 1953 
(124,740) and declined to a low in 1976 (4,703). The long-term 
population average for the Chesapeake Bay was 33,642. In the 
1980s the average population was 15,729 which was 58% less than 
the pre-1980s average of 37,560. Trends of the Chesapeake Bay 
ruddy duck populations have been different than those in the 
Atlantic Flyway and North America. Highest numbers of ruddy 
ducks in the Atlantic Flyway are recorded in North Carolina. 
Ruddy duck population trends in the Chesapeake Bay have 
paralleled trends in the Atlantic Flyway and in North America 
indicating that these changes are a continental phenomenon. 
Although the ruddy duck was traditionally a vegetative 
feeder (Cottam 1939), it now is feeding to a greater extent on 
invertebrates (Perry et al. 1981). Increasing numbers of ruddy 
ducks are recorded around cities like Baltimore and Washington, 
D.C. (Wilds 1979), where they are probably feeding on tubificid 
worms (Tubificidae) (Stark 1978). 
Scoter 
Scoter (Melanitta spp.) populations in the Chesapeake Bay 
have been variable (Table 1; Fig. 8). Peak population occurred 
in 1971 (130,900), and then reached a low of 1,551 in 1981. The 
long-term average was 16,760. The average in the 1980s was 
6,565 which is 65% lower than the pre-1980s average of 18,990. 
The average Atlantic Flyway scoter population during the 1980s 
was 57,386. 
Scoters are traditionally invertebrate feeders (Cottam 1939, 
Martin, Zim, and Nelson 1951) although no record of their food 
habits was made by Stewart (1962), Rawls (1978), or Munro (1981) 
for the Chesapeake Bay. Changes in their distribution within 
the Chesapeake Bay may be due to changing food resources and 
should be investigated. 
153 
