Approximately 85% of the Black Ducks were 
in the sections along the eastern shore of 
Chesapeake Bay; 8% were in the sections west 
of the Bay, including Susquehanna Flats, Pa- 
tuxent River and Potomac River sections; and 
7% were in the Coastal section. Nearly one- 
third of the wintering population was in the 
Chester River section alone. Other large 
populations (39% of the total) were inthe East- 
ern Bay, Choptank River, and Blackwater- 
Nanticoke sections. 
Seasonal changes in numbers during 1958-59 
are shown in table 56. The Chester River 
section was the outstanding Black Duck area 
in the region. The Coastal, Choptank River, 
Eastern Bay, Lower Eastern Shore, and Black- 
water-Nanticoke sections also had large num- 
bers of Black Ducks during all five surveys. 
The Upper Eastern Shore section contained 
fairly large populations during fall andspring, 
but only relatively small numbers in winter. 
The central Chester River was the most 
important local concentration area, Other 
local concentration areas included the lower 
Chester River, outer Chincoteague Bay, upper 
Eastern Bay, and the Hooper Island-Elliott 
area of the Lower Eastern Shore section. 
During the warmer months, breeding Black 
Ducks are common in the Chester River, 
Eastern Bay, and Blackwater-Nanticoke sec- 
tions. They are fairly common in the Choptank 
River and Lower Eastern Shore sections; 
uncommon in the Upper Eastern Shore, Sus- 
quehanna Flats, Upper Western Shore, Central 
Western Shore, and Coastal sections; rare in 
the Lower Western Shore and Patuxent River 
sections and in the Upper, Central, and Lower 
Potomac River sections. A very few breed 
locally in the coastal plain interior. 
Food Habits 
The gullet and gizzard food contents of 212 
adult (or fully fledged immature) Black Ducks 
were examined (tables 57-63). In addition to 
the records shown in the tables, food contents 
were analyzed for four Black Ducks shot at 
impoundments in Kent County in November 
and December; and three shot at impoundments 
at Patuxent Wildlife Research Center during 
October, November, and March. The pre- 
dominant foods in the complex of brackish 
estuarine bays and agricultural fields of the 
Chester River, Eastern Bay, and Choptank 
River sections were (table 57): claspingleaf 
pondweed (seeds, leaves, stems, and root- 
stalks), widgeongrass (seeds, leaves, stems, 
and rootstalks), eelgrass (stems and leaves), 
corn (taken chiefly from grain fields), and the 
bivalve mollusk Baltic macoma (Macoma balthica). 
In the fresh estuarine bay marshes in the 
Blackwater-Nanticoke section, the more im- 
portant foods included (table 58): twigrush 
(seeds), Olney three-square (seeds), and fish. 
In the brackish estuarine bay marshes of the 
38 
Blackwater-Nanticoke section, the more im- 
portant foods were (table 59): Olney three- 
square (seeds), widgeongrass (seeds, root- 
stalks and leaves), saltmarsh snails (Melampus 
bidentatus), and fish (chiefly Poecilidae). In the 
salt estuarine bay marshes, the more impor- 
tant foods were (table 60): fish (chiefly Poecili- 
dae), and the seeds, stems, leaves, and root- 
stalks of widgeongrass. The few birds from 
the coastal salt marshes (table 61) had fed 
chiefly on saltmarsh snails (Melampus bidentatus), 
ribbed mussels (Volsella demissa), and the seeds 
of widgeongrass. In estuarine river marshes 
(table 62), seeds of dotted smartweed were 
taken in greatest quantity; other foods taken 
in considerable amounts included: the seeds 
of halberdleaf tearthumb, pickerelweed, ar- 
rowleaf tearthumb, wildrice, common burreed, 
giant burreed, and arrow-arum. In the wooded 
bottomlands along the Patuxent River (table 
63), the principal foods were beechnuts and 
oak acorns; seeds of hornbeam and other 
woody and herbaceous plants; and the gas- 
tropod Amblozis decisum, and other species of 
small mollusks. In the interior impoundment 
areas of Kent County, corn was the predomi- 
nant food. On the impoundments at the Patuxent 
Wildlife Research Center, the more important 
foods were seeds of a variety of herbaceous 
plants. The principal species were: dotted 
smartweed, arrowleaf tearthumb, largeseed 
smartweed, common burreed, rice cutgrass, 
warty panicum, weak bulrush, and cyperus 
(C. strigosus and C. erythrorhizos). 
Data concerning seasonal changes in food 
habits were obtained from the Black Ducks 
shot in brackish estuarine bay marshes of the 
Blackwater-Nanticoke section (table 59), The 
principal foods (those occurring in more 
than 20% of the birds) each month were: 
September, widgeongrass (leaves, stems and 
rootstalks) and saltmarsh snails (Melampus 
bidentatus); October, high-tide bush (seeds), Olney 
three-square (seeds), widgeongrass (seeds), 
saltmarsh bulrush (seeds), and saltmarsh 
snails; November, widgeongrass (seeds, 
leaves, stems and rootstalks), Olney three- 
square (seeds), and twigrush (seeds); Decem- 
ber and January, widgeongrass (seeds, leaves, 
stems and rootstalks), Olmey three-square 
(seeds), and fish (chiefly Poecilidae); March, 
saltmarsh snails; and June, mosquitoes 
(Culicidae, larvae and pupae), saltgrass 
(leaves, stems and rootstalks), adult beetles 
(Coleoptera), and saltmarsh bulrush 
(seeds), 
Food contents of three juvenal Black Ducks 
were examined. All were collected on June 
11, 1954, in salt estuarine bay marshes of 
Somerset County in the vicinity of Dames Quar- 
ter. Two from one brood (less than one-fourth 
grown) had fed entirely on seeds of widgeon- 
grass. The other (about one-third grown) 
contained more than 60 saltmarsh snails 
(Melampus bidentatus) and numerous seeds and 
fruiting stalks of widgeongrass. 
