d that it must have been a social
bird. For all the domestic races are highly social, and none are known to
build or habitually to roost on trees. The awkward manner in which some
pigeons, kept by me in a summer-house near an old walnut-tree, occasionally
alighted on the barer branches, was {181} evident.[317] Nevertheless, Mr.
R. Scot Skirving informs me that he often saw crowds of pigeons in Upper
Egypt settling on the low trees, but not on the palms, in preference to the
mud hovels of the natives. In India Mr. Blyth[318] has been assured that
the wild _C. livia_, var. _intermedia_, sometimes roosts in trees. I may
here give a curious instance of compulsion leading to changed habits: the
banks of the Nile above lat. 28 deg. 30' are perpendicular for a long distance,
so that when the river is full the pigeons cannot alight on the shore to
drink, and Mr. Skirving repeatedly saw whole flocks settle on the water,
and drink whilst they floated down the stream. These flocks seen from a
distance resembled flocks of gulls on the surface of the sea.

If any domestic race had descended from a species which was not social, or
which built its nest or roosted in trees,[319] the sharp eyes of fanciers
would assuredly have detected some vestige of so different an aboriginal
habit. For we have reason to believe that aboriginal habits are long
retained under domestication. Thus with the common ass we see signs of its
original desert life in its strong dislike to cross the smallest stream of
water, and in its pleasure in rolling in the dust. The same strong dislike
to cross a stream is common to the camel, which has been domesticated from
a very ancient period. Young pigs, though so tame, sometimes squat when
frightened, and thus try to conceal themselves even on an open and bare
place. Young turkeys, and occasionally even young fowls, when the hen gives
the danger-cry, run away and try to hide themselves, like young partridges
or pheasants, in order that their mother may take flight, of which she has
lost the power. The musk-duck (_Dendrocygna viduata_) in its native {182}
country often perches and roosts on trees,[320] and our domesticated
musk-ducks, though such sluggish birds, "are fond of perching on the tops
of barns, walls, &c., and, if allowed to spend the night in the hen-house,
the female will generally go to roost by the side of the hens, but the
drake is too heavy to mount thither with ease."[321] We know that the dog,
howeve