402 
SAND MARTIN. 
them to protrude their heads, and they will thus 
suspiciously survey the cause of their alarm until 
it is either removed or forces them to leave the 
nests. Tlie nest is formed of clay agglutinated 
together, and is of a circular form, suited to the 
shape of the rock or building which supports it, 
but completely closed round, except a small hole 
at the upper side for access. The inside is first 
lined with dried grasses, and within with a warm 
coating of feathers. The eggs are of a delicate 
white with reddish brown spots. 
This Swallow is generally distributed over 
middle and southern Europe, but we are igno- 
rant of its range elsewhere. Temminck states 
that it does not extend beyond the tropics. The 
American species, H. bicolor, for some time con- 
founded with it, is distinct, the bird of Europe 
not being known in the New World. 
The upper parts, with the exception of the 
rump, glossy bluish black, with a steel blue 
lustre ; the wings and tail, the latter slightly 
forked, brownish black glossed with bluish ; the 
rump pure white, appearing most conspicuously 
during flight ; under parts of the same pure 
colour. Difference between the sexes is very 
trifling. 
The Sand Martin, Hirundo riparia, Linn. 
— II. riparia of authors. — Cotile riparia, Boje. 
— Sand or Water Swallow or Martin of British 
authors. This Swallow, with a few others, has 
