of submerged aquatics also occur in the 
marshes along the ''necks'' of Baltimore and 
Harford Counties. Principal species include 
wildcelery, southern naiad, common water- 
weed, grassleaf pondweed, muckweed, coon- 
tail and muskgrass. 
Waterfowl 
The characteristic species of waterfowl 
during the migration periods are: 
Primary Species 
Canada Goose Black Duck 
Secondary Species 
Whistling Swan Shoveler 
Mallard American Widgeon 
Gadwall Ring-necked Duck 
Pintail Common Merganser 
Green-winged Teal American Coot 
Blue-winged Teal 
Wintering and breeding populations of water- 
fowl in the fresh estuarine bay marshes 
usually are comparatively small. Wintering 
populations are extremely variable from year 
to year. During mild winters, fairly large 
populations are often present, whereas during 
severe winters, when most of the ponds and 
creeks freeze over, waterfowl are scarce or 
absent. Only a few scattered pairs of Black 
Ducks breed in the fresh estuarine bay 
marshes. 
Canada Geese and Black Ducks are the two 
commonest waterfowl during the migration 
periods. Canada Geese come to the larger 
shallow ponds, particularly those that con- 
tain stands of Olney three-square and its 
associates. Black Ducks, Green-winged Teal 
and Blue-winged Teal are more numerous 
along ponds and creeks of the central drainage 
systems, where mud flats are exposed at low 
tide, Large numbers of Mallards and Pintails 
occasionally concentrate near managed draw- 
down impoundments and grain fields, Ring- 
necked Ducks (and occasionally other diving 
ducks) generally prefer the deeper ponds, 
whereas Whistling Swans, Gadwalls, American 
Widgeons, and American Coots prefer ponds 
with water that is clear enough to contain 
submerged plants. 
Sample counts, covering approximately 6 
square miles of habitat in Dorchester County, 
were made during the period 1946-57, Results 
are shown in table 12. Numbers probably are 
higher than they would be for the habitat as 
a whole, because most of the counts were 
made on Savannah Lake, which is unusually 
favorable for waterfowl. 
The gullet and gizzard food contents of 28 
waterfowl collected in fresh estuarine bay 
marshes of Dorchester County during the 
18 
migration periods were examined. The most 
important plant foods were twigrush (seeds), 
Olney three-square (seeds and rootstalks), 
common three-square (rootstalks), clasping- 
leaf pondweed (leaves and rootstalks) and 
widgeongrass (leaves and rootstalks). Animal 
foods of some importance, particularly to Black 
Ducks, include killifish (Fundulus sp.), amphipod 
crustaceans (Gammaridae), and midge larvae 
(Chironomidae), 
ESTUARINE RIVER MARSHES 
Estuarine river marshes have become es- 
tablished wherever tidewaters have extended 
inland from the broad estuarine bays along 
narrowed valley floors of tributary streams. 
This habitat occupies about 67,000 acres in’ 
the Upper Chesapeake region. Because the 
channels become progressively narrower in- 
land, variation in tide levels usually is greater 
than it is farther out toward the bay. Estuarine 
river marshes of various sizes are scattered 
throughout the Upper Chesapeake region. The 
largest, along the Nanticoke River, is as 
much as 2 miles wide in places. Other large 
marshes are along the Patuxent, Elk, Chester, 
Choptank, Transquaking, Chicamacomico, 
Wicomico (Wicomico Co., Maryland) and Poco- 
moke Rivers. Small marshes are along nu- 
merous small tidal streams. 
Vegetation 
Vegetation varies from one area to another, 
The major differences are produced by dif- 
ferences in salinity. 
The largest area of fresh estuarine river 
marsh is along the Patuxent River, above 
the mouth of Lyons Creek, Other fairly large 
areas are along various tributaries of the Poto- 
mac River between the District of Columbia 
and Potomac Creek; on the Elk River; and 
along the upper tidewater portions of the Chop- 
tank and Wicomico Rivers (Wicomico River 
of Wicomico County), 
The vegetation of typical fresh-water areas 
is composed of a great variety of emergent 
marsh plants, including many species that 
occur in the interior beyond tidewater, Charac- 
teristic species include: 
Primary Species 
Dotted Smartweed 
Halberdleaf Tearthumb 
Tidemarsh Waterhemp 
Narrowleaf Cattail 
Broadleaf Arrowhead 
Rice Cutgrass 
Wildrice Spatterdock 
Walter Millet Jewelweed 
River Bulrush Rosemallow 
Arrow-arum Marsh Beggartick 
Pickerelweed 
