THE COMMON SWALLOW. 
383 
then influences them is, the production of their species ; and no 
matter how favourable every circumstance may be for migration, 
they do not leave the country. I have attended to the departure 
of the Hirundines for many years, and to the influencing causes, 
and was at first surprised at the suddenness of their disappear- 
ance when favourable weather arrived. At the end of August, 
I have known the great body to depart, and at other times re- 
marked them evidently waiting for weeks, and on to the month of 
October, before they would take their flight. 
Perching. In perching, the swallow, unlike the swift, occasion- 
ally rests upon the ground by choice, roads being not uncom- 
monly thus resorted to. On the sandy, and even the gravelly 
sea-beach, I have remarked them to alight in the autumn to 
repose, though objects were rarely picked up from the sand. 
I have observed a number of these birds daily frequenting 
a large mound of clay in the vicinity of houses throughout 
the month of August, long subsequent to the time that such 
material is required for their nests. On the occasions upon 
which I particularly remarked the circumstance, food was cer- 
tainly not the object — the birds were simply resting. Mr. Mac- 
gillivray says of the swallow, that “ it sometimes alights [on the 
ground] as if to pick up insects, which it has observed there,” 
(Brit. Birds, vol. iii. p. 564.) and such, we may expect is 
occasionally done. On betaking themselves to trees, they generally 
exhibit a singular choice in avoiding the flourishing branches and 
alighting on those which are dead. It has been remarked to me 
by Mr. Wm. Sinclaire, that so soon as the young can provide for 
themselves, they do not return to the nest in which they were 
reared ; from which circumstance, and from seeing large flocks of 
swallows fly in the autumnal evenings around the highest trees at 
his residence, and invariably disappear in their direction, he con- 
cludes that they roost on trees. White of Selborne, speaking 
generally of these birds, mentions their thus roosting late in 
autumn. 
Frequenting the sea. The same author remarks, that “the 
swallow is a bold flyer, ranging to distant downs and commons 
