24 BULLETIN 672, U. S. DEPARTMENT OF AGRICULTURE. 
and mallards were not far behind in this respect. Some of the birds 
treated in this way became tame at once, while others seemed never 
to lose their sense of fear. 
Birds vary somewhat in the degree to which they are affected and in 
the manner in which they recover. A few pintails and green-winged 
teal handled during 1916 seemed to suffer some breakdown of the 
nervous system as a result of the severe paralysis. As these indi- 
viduals recovered from their helpless condition they had little or no 
control over their muscular movements, though they seemed normal 
in other ways. There was a constant trembling of the head, and 
with any attempt at movement head, wings, and feet were thrown 
about convulsively. As it raised its head in attempting to drink, 
such a bird might throw itself completely over, or in trying to swim 
to shore might dash in circles about the pen, turning over and over. 
Birds affected in this way, however, were comparatively rare. None 
of those under observation recovered. 
Birds that are seriously sick get very thin as they recover, but 
soon regain their normal flesh. Sick ducks in captivity should be 
fed morning and evening. The writer used wheat and barley mixed 
in equal parts as food for the larger ducks. Teal seldom eat any- 
thing but wheat. The grain was placed in shallow wooden troughs 
5 feet long, from 4 to 6 inches wide, and 1^ to 2 inches deep. These 
troughs were placed across the pen a foot or so from the edge of the 
water. In this way the grain was brought to the notice of the birds 
as they went in and out of the water. In addition to grain it is well 
to have a small pan of grit in each pen. 
During hot weather half of each pen should be covered with rushes 
in order to protect captive birds from the sun. Though able to 
endure intense heat when free, birds may succumb when confined in 
a narrow space unless protected. On Bear River it was necessary 
to inclose that part of the pens projecting into the water as a pro- 
tection against the inroads of the numerous carp. Along the river 
banks in low water during summer a margin of mud is exposed that 
separates the roots of the riparian vegetation from the water. This 
deprives the carp of a large part of their natural f eeding grounds, so 
that grain and excrement about the duck pens proved a great attrac- 
tion to them and they frequently dug out the mud under an entire 
pen in the course of a night. Racks 6 or 8 feet long were made of 
lath sharpened at one end and nailed to crosspieces, with half -inch 
spaces. With these a fence was built in the water 3 feet beyond the 
pens and the same distance from either end. This permitted free 
circulation of water and at the same time kept the carp from digging, 
as the lath were sunk from 6 to 12 inches in the mud. It is neces- 
sary to fill in the duck pens from time to time, as the more active 
ducks continually dig away the mud from the shore. 
