SUMMARY AND CONCLUSIONS 
The Upper Chesapeake region is the chief 
focal point along the Atlantic coast for vast 
numbers of migrating waterfowl. Average 
wintering populations of Whistling Swans, 
Canada Geese, Black Ducks, and Canvasbacks 
in the years 1953-58 were the largest known. 
Very large numbers of American Widgeons, 
Redheads, Lesser Scaup, and Ruddy Ducks 
also winter in the region and migrate through 
it. Fairly large numbers of many other species 
also are present. Breeding populations of 
waterfowl in the region also are of considerable 
importance, at least locally: breeding Black 
Ducks are common in certain areas along the 
eastern shore of Chesapeake Bay, and scat- 
tered pairs of breeding Wood Ducks are fairly 
evenly distributed throughout the region. 
Wintering waterfowl populations in the region 
during recent years have averaged more than 
1,000,000 birds, and represent about 4% of the 
continental wintering population and 23% of 
the Atlantic population. The diving ducks are 
more abundant than other groups of waterfowl. 
The predominant species, however, include 
a general mixture of diving ducks, dabbling 
ducks, and geese. The combined numbers of 
Canvasbacks, Canada Geese, Black Ducks, 
and scaup, constitute more than half of the 
average wintering population. 
Waterfowl populations gradually increase 
during the fall migration, reaching a peak in 
December. A slight reduction normally occurs 
in winter and then a gradual decrease during 
the spring flight. Dabbling ducks generally 
predominate in the fall, whereas diving ducks 
are proportionally more numerous in winter 
and spring. American Widgeons are the com- 
monest waterfowl during the early fall flight; 
Canada Geese, Black Ducks, Canvasbacks, 
and scaup are among the more numerous 
waterfowl during late fall, winter, and early 
spring. 
Thirteen major types of waterfowl habitat 
are defined, and the annual and seasonal 
variations in their waterfowl populations are 
described. These habitats include six in open 
tidewater areas: fresh, slightly brackish, 
brackish, and salt estuarine bays, coastal 
bays, and the littoral zone of the ocean. Five 
of the habitats are types of tidal marshes: 
coastal embayed marshes, salt, brackish, 
and fresh estuarine bay marshes, and estuarine 
river marshes. The other two major habitats 
are within the coastal plain interior and are 
designated as wooded bottomlands and interior 
impoundments. 
The brackish estuarine bays are the most 
important habitat for waterfowl populations as 
a whole. Certain waterfowl such as Whistling 
Swans, American Widgeons, Canvasbacks, and 
American Coots occur regularly in winter 
throughout brackish estuarine bays. Others, 
including Canada Geese, Mallards, and Black 
62 
Ducks, are more restricted to areas that are 
adjoined by extensive grainfields. Fresh es- 
tuarine bays, brackish estuarine bay marshes, 
and estuarine river marshes also attractlarge 
numbers of waterfowl of many kinds. Other 
habitat types are of importance to fewer 
species. 
Local differences in waterfowl populations 
within the region prove to be closely corre- 
lated with local variations in the preponderance 
of the different habitats. In some years, the 
distributional pattern also is influenced by 
extreme weather conditions. Locally, pollution 
and turbidity of estuarine waters, and exces- 
sive human disturbance, are important in 
affecting the distribution of waterfowl popula- 
tions. Fifteen biogeographical sections are 
defined on the basis of kinds and proportions 
of habitats and abundance and kinds of water- 
fowl, These sections include: Upper Potomac, 
Central Potomac, Lower Potomac, Patuxent 
River, Lower Western Shore, Central Western 
Shore, Upper Western Shore, Susquehanna 
Flats, Upper Eastern Shore, Chester River, 
Eastern Bay, Choptank River, Blackwater- 
Nanticoke, Lower Eastern Shore, and Coastal. 
The greatest concentrations of transient 
and wintering waterfowl occur along the central 
eastern shore of Chesapeake Bay in the 
Chester River, Eastern Bay, and Choptank 
River sections. Brackish estuarine bays with 
large adjoining agricultural fields are the 
principal waterfowl habitats in these sections. 
During some years, the Blackwater-Nanticoke 
section, which contains extensive fresh and 
brackish estuarine marshes, also had large 
numbers of waterfowl. The Susquehanna Flats, 
with their luxuriant beds of fresh-water sub- 
merged plants, were one of the principal 
concentration areas during the spring and 
fall migration periods. Sections that contained 
moderate numbers of waterfowl were: Central 
Potomac, Upper Western Shore, Upper Eastern 
Shore, Lower Eastern Shore, and Coastal. 
Sections with relatively few waterfowl were: 
Upper Potomac, Lower Potomac, Patuxent 
River, Lower Western Shore, and Central 
Western Shore. 
The quality of habitat in many areas form- 
erly important to waterfowl has deteriorated 
greatly during recent years, Factors respon- 
sible include: pollution and turbidity of fresh 
and slightly brackish estuarine waters; en- 
croachment of pest plants and animals, in- 
cluding the waterchestnut, Eurasian water- 
milfoil and carp; use of marshes and other 
habitats for spoil and trash disposal, and the 
commercial development of these so-called 
waste lands; ditching of marshes for mosquito 
control; and destruction of beds of submerged 
aquatic plants through clam-dredging opera- 
tions or by more direct control measures 
designed to improve swimming and boating. 

