148 
POPULAE HISTORY OF BIRDS. 
their own nest^ which^ like the roof^ they construct of coarse 
grass ; these are placed side by side against the under sur- 
face of the general covering; and^ by the time they are all 
completed^ the lower surface of the mass exhibits an appear- 
ance of an even horizontal surface^ freely perforated by small 
circular openings. 
^''They never use the same nests a second time^ though 
they continue for many years attached to the same roof. 
With the return of the breeding season^ fresh nests are 
formed upon the lower surface of those of the previous year^ 
which then form an addition to the general covering. In 
this manner they proceed^ year after year adding to the 
mass^ till at last the weight often becomes such as to cause the 
destruction of its support^ upon which a new building-spot 
is selected. They appear to prefer constructing these nests 
upon large and lofty trees ; but^ where such do not occur^ 
they will even condescend to form them upon the leaves of 
the arborescent aloe^ as occasionally happens towards the 
Orange river. 
"The commencement of the roof is firmly interwoven 
with the branches of the trees to which it is intended to be 
suspended ; and often a great part of a principal branch is 
actually included within its substance.''^ Dr. Andrew Smith 
