migration period extends from February 20 - 
March 1 to May 1-10, with the peak between 
March 1 and April 20. A high local count 
of 19,000 Surf Scoters was made on March 1, 
1955, in the littoral zone of the ocean between 
Ocean City, Maryland, and the Delaware - 
Maryland line. Another high count of 5,400 was 
made in the Ocean City area on December 
27, 1954, 
COMMON SCOTER 
Oidemia nigra (Linnaeus) 
Transient and wintering Common Scoters 
usually are restricted to the Coastal section, 
where they frequently are quite common, 
although usually less so than either the Surf 
or White-winged Scoters. The largest popu- 
lations of Common Scoters generally are in 
the littoral zone of the ocean. A few Common 
Scoters occur regularly on the coastal bays, 
and occasionally on salt and brackish estua- 
rine bays of Chesapeake Bay proper. 
The fall migration usually is during the 
period from September 10-20 to November 
20-30, with the peak between October 10 and 
November 10, The normal spring migration 
period extends from February 10-20 to May 
5-15, with the peak between February 25 and 
April 25. High local counts include 6,300 on 
April 6,1946, in the littoral zone of the ocean 
between Ocean City, Maryland, and the Dela- 
ware - Maryland line; and 2,400 in the Ocean 
City area on December 27, 1954, 
RUDDY DUCK 
Oxyura jamaicensis (Gmelin) 
Migrant and wintering Ruddy Ducks are 
very numerous in the Upper Chesapeake re- 
gion, although their distribution usually is 
somewhat "spotty'', In certain areas, Ruddy 
Ducks are abundant, whereas in other areas 
they are quite scarce, January inventories 
for 1953-58 showed that the wintering popula- 
tions ranged from 21,400 in 1956 to 102,700 
in 1953, averaged approximately 62,400. This 
average figure represents about 27% of the 
continental wintering population, and about 59% 
of the Atlantic population. Ruddy Ducks are 
unwary, and most hunters consider them 
third-rate gamebirds and shoot them only as 
a last resort, when other ducks are not 
available, Fall migration of Ruddy Ducks usu- 
ally is during the period from September 15- 
25 to December 5-15, with the peak between 
October 25 and November 30. The normal 
spring migration period extends from March 
1-10 to May 10-20, with the peak between 
March 15 and April 10. 
58 
Habitats 
The largest concentrations of transient and 
wintering Ruddy Ducks are on the slightly 
brackish estuarine bays of the Upper Western 
Shore and Central Potomac sections. Con- 
siderable numbers also are in brackish es- 
tuarine bays and occasionally fairly large 
flocks are present on salt and fresh estuarine 
bays. Ruddy Ducks ordinarily are not present 
on the coastal bays or ocean. Scattered in- 
dividuals or small flocks may sometimes occur 
on ponds and creeks of the various tidal 
marshes, and, during the spring and fall, 
migrating flocks may stop at interior im- 
poundments for short periods, 
January inventories for 1955-58 showed 
the wintering populations distributed over 
the major habitat types as follows: slightly 
brackish estuarine bays - 54%; brackish es- 
tuarine bays - 41%; salt estuarine bays - 
5%; and fresh estuarine bays - 1%, 
Ecological distribution during the 1958-59 
season is shown in table 141. Ruddy Ducks 
differ from other common species of water- 
fowl in that they occur in the greatest con- 
centrations in slightly brackish estuarine bays, 
chiefly on the Patapsco and Potomac Rivers, 
and are present there throughout the season. 
Considerable numbers also are present on 
fresh and brackish estuarine bays. The high 
count shown in the table for salt estuarine 
bays during January probably is exceptional. 
Biogeographic Sections 
The average distribution of wintering popu- 
lations during 1955-58 is shown in table 142. 
Nearly four-fifths of the wintering population 
was in the Lower Potomac, Central Potomac 
and Upper Western Shore sections. The prin- 
cipal concentration area on the Potomac River 
lies between Nanjemoy Creek and Breton Bay, 
whereas the major area within the Upper 
Western Shore section is along the Patapsco 
River. Other areas where there were local 
populations of considerable size include: Fish- 
ing Bay and the Nanticoke River onthe eastern 
shore; the Magothy, Severn, South, Rhode, and 
West Rivers of the central western shore; and 
the Patuxent River. Ruddy Ducks were rela- 
tively scarce or absent elsewhere. 
Seasonal changes in numbers during 1958-59 
are shown in table 143. The population peak 
was reached during the fall migration in No- 
vember, but the greatly lowered population 
in January may have resulted from the un- 
usually severe weather that winter, The 
Upper Western Shore and Central Potomac 
sections were the major concentration areas 
during the surveys. The unusually large pro- 
portion of Ruddy Ducks recorded in the Lower 
Western Shore section in January probably 
was due to the severe weather conditions at 
that time, for the comparatively deep, salt 
