300 
BIRD-LIFE. 
while they are engaged in constructing their nests and 
rearing their young as one of the most pleasurable 
occupations of the naturalist. This offers to man an 
extensive field: he can glance deeply into the household 
life of birds, and thus study their every-day economy. 
Almost every bird has its peculiar habits, and each 
displays some characteristic exclusively its own; their 
social or unsocial habits are never more openly displayed 
than during the breeding season. The construction of 
their different nests is so various, that the examination 
of these alone is a highly interesting employment. 
Most birds build their nests in the centre of their 
particular beat, and in the situation best adapted for 
that purpose, without troubling themselves further 
about other members of their own species ; yet there are 
many which flock together in great numbers during the 
breeding season, and proceed to build, in company, as 
soon as they have found a suitable locality. Such 
colonies may equally consist either solely of members of 
one species or of different species, some even belonging 
to very opposite families ; but a certain community of 
habits is necessary for the formation of such assem¬ 
blages. Marsh and swimming birds, aquatic in their 
habits, are drawn together by their common necessity— 
water, and though the colony may embrace a great variety 
of species they live together in the greatest harmony, 
while similar assemblages of land-birds consist always 
of one and the same species. Common nesting places 
are generally used repeatedly, whereas isolated nests, 
with the exception of those of the larger birds of prey, 
Crows, Woodpeckers, and especially of those birds which 
breed in holes, and of some solitary breeding marsh- 
bird, are renewed every year. The situation and 
