182 BRITISH BIRDS. 
it. Sometimes they will visit heaps of mortar, or the dusty roads which have 
just been watered. The outside shell of the nest is almost entirely com- 
posed of mud. The birds do not build much at a time, but allow one layer 
to dry before another is placed, so that each nest takes ten days or a fortnight 
to finish. The mud is brought in little pellets, and a few straws or dry 
grass, or even hair, are intermixed to bind it together. Sometimes two 
or three nests are built together; and in some localities they are placed in 
rows one under the other. The inside is lined with dry grass and a few 
feathers. The nest is rounded in form, the quarter of an upright oval 
globe, and the hole which admits the birds is at the top, generally in the 
middle, but often in one corner. The lining materials are chiefly collected 
as the bird is on the wing—straws and feathers which the wind blows into 
the air. If their nest is destroyed the birds soon commence another on 
the ruins of the old one, and this has been known to be repeated many 
times in succession. The nest is a somewhat large structure, often 
measuring eight or nine inches in external diameter; the mud walls vary 
from half an inch to three quarters of an inch in thickness. It has been 
said that the bird sticks the little mud pellets that form the outside of its 
nest together with its saliva. 
The Martin begins to build its nest or to repair its old one about a month 
after its arrival, and fresh eggs may be obtained in Greece and Asia Minor 
as early as the end of April, but seldom in this country before the end of 
May. In the extreme north of Europe eggs are not to be obtained until 
several weeks later. Curiously enough, in Algeria the Martin does not 
appear to breed any earlier than in this country ; at Philippeville, on the 
coast, Dixon remarks that their nests were unfinished in the middle of May. 
The eggs of the Martin are from four to six in number. They are pure 
glossy white, and the shell is very smooth. They vary in length from ‘8 to 
‘7 inch, and in breadth from *55 to ‘52 inch, and very closely resemble those 
of the Sand-Martin, but are a trifle larger, somewhat coarser grained, but 
more polished. 
Both birds assist in incubating the eggs ; and when the young are hatched 
the exertions of the parents are taxed to the utmost to find them a suf- 
ficient supply of food. A correspondent of Macgillivray’s (Mr. T. D. 
Weir) states that in one day they fed their young three hundred and seven 
times! During the whole period of incubation the male roosts in ,the 
nest with the female. When the young can leave the nest they are fed 
and tended by the old birds until they are strong on the wing, and during 
this time the little family-party always sleep in the nest at night. The 
young birds are fed upon the wing by their parents, and often perch on 
posts, fences, or even telegraph-wires, waiting for the old birds to catch 
flies for them. Probably most pairs of birds attempt to rear a second 
brood in the season; but in some cases the hereditary impulse to migrate 
