Populations increased in the mid-1960s as a result of better 
conditions on the breeding grounds and to restrictive hunting 
regulations. Canvasback numbers, however, decreased again in 
the late 1960s, and in 1972 the hunting season on canvasbacks 
was closed. The long-term average population of canvasbacks in 
the Chesapeake Bay was 104,012 in the 1980s the population 
averaged 52,931, which was 54% lower than the pre-1980s average 
of 115,811. In 1986 canvasback in the Bay were at an all-time 
low of 34,300. Canvasback populations in the Chesapeake Bay 
during the 1970-80s have been relatively stable despite in¬ 
creasing number of canvasbacks in the Atlantic Flyway and North 
America. The phenomenon led Perry et al. (1981) to speculate 
that habitat degradation in the Bay was adversely affecting 
numbers of wintering ducks. 
When SAV beds in the Bay declined the canvasback was forced 
to seek alternate food sources. It did this much more effec¬ 
tively than other duck species, and now the Chesapeake Bay 
canvasbacks feed predominantly on molluscs (Perry et al. 1981). 
This food source, however, is not considered to be as nutri¬ 
tionally sound as the high energy plant tubers upon which it 
formerly fed (Perry et al. 1986). 
Redhead 
Redhead (Aythya americana) population numbers in the 
Chesapeake Bay are on a long-term downward trend (Table 1; Fig. 
5). Although there was a peak number of redheads in 1956 
(118,800), this population has steadily declined to a low of 
only 800 ducks in 1983. The long-term average was 35,288 
redheads. During the 1980s the average winter population 
recorded in the Bay was only 3,506 which was 92% less than the 
pre-1980s average of 42,240. Most of these ducks are seen in 
the Tangier Island area. An average of 97,914 redheads were 
recorded in the Atlantic Flyway during the 1980s, indicating 
that population declines in the Chesapeake Bay have been more 
drastic than in other areas. 
Unlike the canvasback, the redhead did not change its food 
habits as habitat conditions changed. It still feeds on the 
upper vegetative parts of submerged aquatics. With the loss of 
SAV in the Bay, redhead populations in the Bay declined, and now 
redheads are most abundant in North Carolina, Florida, and Texas 
where SAV is abundant. Because the redhead is now wintering in 
different areas than the canvasback, hunting regulations are no 
longer the same as they were historically. 
Scaup 
Scaup populations in the Chesapeake Bay consist of two 
species, the greater (Aythya marila) and lesser (Aythya affinis) 
scaup. Scaup (Table 1; Fig. 6) in the Chesapeake Bay peaked in 
1954 at 403,658 and then declined in the late 1950s. 
151 
