28 
ANAS BOSCHAS 
dead salmon. Near Juneau, Alaska, they live during the winter on mussel and bar- 
nacle beds and get very rank (A. M. Bailey, MS.). Decaying vegetable matter also 
is occasionally consumed. In Scotland, C. St. John (1882) found them eating the 
remnants of diseased potatoes, and preferring them even to corn. In Ayrshire forty 
or fifty Mallards would visit one potato pit (R. Gray, 1871). One writer speaks of 
their going to potato fields at night to feed on the small potatoes which lie about 
upon the surface, and they are said to eat rotten apples in Sussex (Owen, 1895). The 
following fruits have occasionally been found in their stomachs: blackberries in 
Cheshire (H. W. Robinson, 1917), blueberries in Norway (Collett, 1869), plums 
and similar fruits (Naumann, 1896-1905). Their habit of feeding in oak woods has 
already been mentioned, but this practice is probably not so common as formerly. 
A large flock feeding in a wood is said not to run along the ground as might be sup- 
posed, but the hindmost ones constantly fly over those in front, leap-frog fashion, 
so that the progress is at least ten miles an hour, the whole producing a “roar like 
distant thunder” (Gasper, 1893). During a hard winter they fed so commonly on 
acorns in an English park that the following year hundreds of acres were covered 
with seedling oaks (Feilden, 1891). 
Attention has recently been called to the swallowing of mosquito larvae by 
Mallards (McAtee, Auk, vol. 28, p. 287, 1911) and Dixon has gone so far as to recom- 
mend the keeping of tame Mallards as a means of exterminating mosquitoes on in- 
fested ponds. He quotes his own experiments in this direction (Journ. Amer. Med. 
Assoc., p. 1203, 1914). Tame birds have been very useful in exterminating slugs from 
vegetable gardens. W. Thompson (1851) enters into this subject in some detail. 
Very degenerate habits are occasionally developed among semi-domesticated birds. 
They have been known to kill and eat sparrows, and to plunder the nests of smaller 
birds (Liebe, Ornith. Monatsschr., 1894, p. 15; Wacquant, ib{d., p. 89). 
Before leaving the subject of food, the Mallard’s habit of eating shot should be 
mentioned. It w’as noted in Italy as long ago as 1786, and has apparently caused the 
death of many birds there (Savi, 1827-31, vol. 3, p. 161). G. B. Grinnell (1901) 
called attention to this phenomenon as seen in specimens taken in Texas and North 
Carolina. The subject has often been discussed in sportsmen’s journals in this coun- 
try, and W. L. Dawson and Bowles (1909) mention two Mallards found on the 
Nisqually Flats, Washington, one of which contained nineteen and the other twenty- 
seven pellets, while there were marked pathological lesions in the stomachs and large 
intestines. Recent experiments by the United States Biological Survey (Wetmore, 
1919) show that two or three number-six shot ingested will sometimes cause death, 
and that six pellets are always fatal. Mallards seem to eat shot much oftener than 
other ducks, but Pintails, Canvas-backs and Whistling Swans have been found 
suffering from lead poisoning. 
It is necessary for ducks to fill the crop at least twice a day, if not oftener. On 
