Results of sample counts of waterfowl in 
fresh estuarine bays from September to April 
are shown in table 5. Approximately 135.5 
Square miles were covered in the surveys. 
The counts of different areas were quite 
variable, primarily because of the very large 
local concentrations of diving ducks. The 
highest populations were in December, and 
the lowest in September. 
The gullet and gizzard food contents of 147 
waterfowl collected in fresh estuarine bays 
were examined. From these, certain general- 
izations can be made concerning food habits. 
The principal foods were: wildcelery (leaves, 
stems and rootstalks); various pondweeds, 
chiefly sago pondweed, claspingleaf pondweed, 
grassleaf pondweed, and southern naiad 
(leaves, stems, rootstalks and seeds); and 
various species of small gastropod (univalve) 
mollusks, chiefly Ozytrema virginica, Gyraulus sp., 
and Amnicola imosa. Other foods occasionally 
taken in fairly large quantities include: corn 
(taken as illegal bait or innearby grainfields); 
aquatic insect larvae, chiefly caddisflies({Tri- 
choptera) and mayflies (Ephemeroptera); and 
small fish, chiefly minnows (Cyprinidae) and 
sunfish (Lepomis sp.). 
SLIGHTLY BRACKISH ESTUARINE BAYS 
Slightly brackish estuarine bays (fig. 2) in 
the Upper Chesapeake region amount to ap- 
proximately 182,000 acres. This includes about 
24,000 acres of shoal waters. 
There are two major and several minor 
areas of this habitat. One major area is the 
central portion of the Potomac River estuary, 
from Cobb Island to Maryland Point (Charles 
County, Maryland), including the Wicomico 
and Port Tobacco Rivers and Nanjemoy Creek. 
The other major area is along the upper 
western shore of Chesapeake Bay, from Pine- 
hurst in Anne Arundel County to Leges Point 
on Gunpowder Neck (Harford County), including 
the Patapsco River, Back River, Middle River, 
Seneca Creek, and the lower portion of the 
Gunpowder River. A minor area extends along 
the upper eastern shore of Chesapeake Bay in 
Kent County from Swan Point to Worton 
Point. Other smaller areas are in the upper 
portions of the Magothy and Severn River es- 
tuaries. 
Vegetation 
Luxuriant growth of submerged aquatic 
plants occurs in the shallower zones of all 
areas, except for areas that have been heavily 
polluted with domestic or industrial wastes. 
The predominant species are claspingleaf 
pondweed, wildcelery, and widgeongrass, Other 
Species that are widely distributed and fairly 
common locally include sago pondweed, horned 
pondweed, southern naiad, common waterweed, 
grassleaf pondweed, muskgrass, and certain 
types of red algae. Scattered patches of 
muckweed and coontail also are present ina 
few areas. Many of the more sheltered coves 
and tributary tidal streams in the Potomac 
River area are choked with dense, nearly 
pure, stands of the introduced Eurasian water- 
milfoil. This aggressive plant has become a 
serious pest and a real danger to the remain- 
ing beds of native submerged plants. 
Invertebrates 
Invertebrates were not studied in detail. 
General observations indicated that the bi- 
valve Macoma phenaz is one of the major spe- 
cies. Barnacles (Balanus sp.) also were noted 
occasionally. The invertebrate fauna in gen-~ 
eral probably is somewhat intermediate be- 
tween that of brackish estuarine bays and that 
of fresh estuarine bays. 
Waterfowl 
In early fall and in winter, approximately 
7% of the waterfowl population of the Upper 
Chesapeake occurs in slightly brackish es- 
tuarine bays. From 9% to 14% of the population 
is here in the late fall and early spring. 
Most waterfowl areas in this habitat are 
subject to considerable human disturbance in 
the form of boating, excessive hunting pres- 
sure, artillery firing from adjacent military 
reservations, and domestic and industrial 
pollution from nearby cities and factories. 
These activities definitely limit waterfowl use. 
Characteristic species of transient and win- 
tering waterfowl are: 
Primary Species 
American Widgeon 
Redhead (local) 
Canvasback 
Lesser Scaup 
Ruddy Duck 
American Coot 
Secondary Species 
Ring-necked Duck 
Common Goldeneye 
Bufflehead 
Common Merganser 
Whistling Swan 
Canada Goose 
Black Duck 
Gadwall (local) 
Other species occasionally observed in small 
numbers include the Mallard, Pintail, Green- 
winged Teal, Greater Scaup, Oldsquaw, Hooded 
Merganser, and Red-breasted Merganser. 
The Ruddy Duck usually is the most abundant 
species in this habitat and also is commoner 
here than in any other habitat. Often there 
are large local concentrations of Redheads, 
especially in the lower Gunpowder River - 
Seneca Creek area during the spring flight. 
Canvasbacks normally are common and wide- 
spread throughout the late fall, winter, and 
