354 
CONCORD AND DISCORD IN BIRDS. 
By combination birds may perhaps discern food, 
and eligible situations the readier; and it is not 
unusual at these times for sentinels to be appointed 
to warn of danger. During migration, a combination 
of individuals may give more facility to their 
transits, and leading birds are often observed to 
be appointed. Yet as before said, many kinds do 
not associate when food is scarce; many birds 
also do not migrate in concert.—Upon the whole, 
we should naturally think it would be more advan¬ 
tageous for birds to remain separate during times 
of scarcity, and therefore, though we do not know 
why they act oppositely in this respect, or why 
many kinds migrate singly, seeing also that asso¬ 
ciations of single birds take place when danger is 
threatened by a rapacious animal or such like 
causes, and that strife concerning food is common 
among apparently very harmonious communities 
in other respects it seems to follow that there is 
some other principle at work inducing them to 
congregate in the several emergencies of their lives. 
This principle I take to be a desire of society, and 
mutual commiseration of suffering. It is worthy 
of note that severity of cold has a most decided 
influence on this propensity to associate. Magpies 
collect in small parties only when the weather is 
severe; at other times they keep pretty much aloof, 
and when thus combined their chances of finding 
sufficient sustenance for the party must, one would 
think, be greatly diminished. The Cirl Bunting 
joins the flocks of Yellow Hammers only in those 
seasons which are very severe; ordinarily they 
keep together in winter in small assemblages, near 
the seat of their summer abode, these little com¬ 
panies being perhaps families. This propensity in 
families to remain united is a very common obser¬ 
vance among birds. I believe also it is more usual 
for pairs to continue together during winter than is 
