28 
A COMMUNITY OF BIRDS. 
exceptions. For instance, the male weaver-birds work quite as assidu- 
ously as their mates. In most cases the male is responsible for the 
safety of the home ; it is only among polygamous birds that he takes 
no interest in its defence. Certain birds construct their nests on the 
socialistic principle ; the females lay their eggs side by side, and sit 
upon them indiscriminately. Others build for the benefit of the com- 
munity an enormous pile, divided into numerous compartments, each 
of which is appropriated to a family. Thus Mi-. Paterson says of the 
sociable grosbeak, which, in all probability, had learned the value of 
association, and congi-egated in communities long before man himself, 
that on one tree, a mimosa, in a South African grove, he saw from eight 
hundred to a thousand of its nests under one general roof " I call it a 
roof," he says, " because it resembles that of a thatched house, and pro- 
jects over the entrance of the nest below in a very singular manner. 
The industry of these birds seems almost equal to that of the bee. 
Throughout the day they appear to be busily employed in carrying a 
species of fine grass, which is the principal mateiial they employ for 
the jiurpose of erecting this extraordinary work, as well as for addi- 
tions and repairs. When the tree which is the support of this aerial 
city is obliged to give way to the increase of weight, it is obvious that 
they are no longer jirotected, and are under the necessity of rebuilding 
in other trees. One of these deserted nests I had the curiosity to break 
down, to inform myself of the internal structure ; and found it equally 
ingenious with that of the external. There are manv entrances, each 
of which forms a regular street, with nests on both sides at about two 
inches' distance from each other. The grass with which they build is 
called the ' bushman's grass.' From every appearance, the nest which 1 
dissected had been inhabited for man}- years, and some parts were more 
complete than others. This, therefore, I conceive to be an additional proof 
that the animals added to it at diff"erent times, as they found necessary 
from the increase of the famil}', or, rather, of the nation or communit}'." 
MIGRATIONS. 
The bird is a great traveller. Many families, after they have 
brought up their young to take care of themselves, undertake voyages 
