‘vot. x1.} NESTING OF THE SWALLOW. 227 
Each time when one parent is heard bringing food, the other 
slips off the nest: it is unusual to see both at the nest 
together. After the food has been disposed of, the gapes 
of the young are examined, and undigested matter removed. 
This is necessary as the young are fed on many kinds of 
flies and small moths, and many parts of flies are quite 
impossible for young birds to digest. Then the feces are 
looked for and dealt with. If the bird remains at the nest 
the well of the nest is cleaned up, and then the bird broods. 
The parents seem to bring very little food at each visit 
and, as a rule, only one young one gets ied. Visits are, on 
an average, paid to the nest rather oftener than once in 
three minutes, according to my notes: at times very much 
oftener. The old birds are very alert while brooding, and 
the head is almost always on the move; this is not nearly 
so much the case during incubation. 
The usual length of the nestling period is twenty-one days. 
I have known the young stay as long as twenty-four days, 
and shorter periods than twenty-one have been recorded. 
The young can always fly well before they leave the nest. 
Sometimes they leave the nest to return to it to rest at 
intervals during the day. At other times this rest is taken 
on roofs: they will perch on wires, but cannot stand thus 
for long and do not seem to get real rest in such a position 
until they are somewhat older. At night the young all 
collect in the nest for a considerable period, especially the 
last brood of the year. The parent birds do not seem to 
roost anywhere near the young after some two nights or so 
before the end of the nestling period. 
While the young are in the nest they seem to recognize 
flying insects as food, for they always try to capture those 
that come within reach. After leaving the nest they have 
to be fed by the parents for some time. While they usually, 
and especially at first, receive the food while they are perched 
or sitting on a roof, it is a common enough sight to see them 
fed on the wing. Both birds fly upwards, as it were along 
the arms of an inverted V, and when they meet at the point 
there is a distinct pause long enough for the food to be 
transferred. 
