BREEDING COLONIES. 
339 
scarcely be constructed by human hands. Near the town 
of Koptos there is an island sacred to Isis, which these 
Swallows have fortified in a similar manner to preserve 
themselves from the flood. In the early spring they 
strengthen the facade with straw and chaff, continuing 
their labours night and day for three consecutive days, 
with such assiduity that many expire from exhaustion. 
This work has to be renewed every year.” Many travellers 
have mentioned these Swallows, whose habits of nidifica- 
tion they have only observed at a distance, and speak of 
them, if not in terms so eulogistic as those employed by 
Pliny, yet with astonishment. 
Both Northern and Southern Europe afford similar 
examples of these colonies. In the North they are Sea¬ 
birds, which we find congregating together in such vast 
flocks during the breeding season; and in the South 
certain species of Marsh-birds, and also Bee-eaters. The 
latter much resemble Sand Martins, both in their general 
habits and mode of building. I have often visited their 
nesting-places on the banks of the Blue Nile. A smooth 
face of the bank is selected, and is regularly perforated to 
a depth of some nine inches, the holes being placed so 
close together as to leave only a very thin partition 
between the oven-like excavation at the further end of 
each hole. In front of the entrances a flock of these 
graceful birds may be seen gliding to and fro in every 
direction; each individual, however, knows his own 
residence, and does not hesitate an instant when swooping 
at the hole. This, be it remembered, occurs where often 
from fifty to sixty holes are to be found bored in a 
surface of less than four-and-twenty square feet, and 
every entrance is alike ! Every prominent branch and 
twig on the neighbouring trees are covered with these 
