368 
BIRD-LIFE. 
feathered summer guests prepare for their usual migra¬ 
tion. Before they leave, though, they once again sing 
their spring ditties; once more revisit their accustomed 
haunts, even the deserted nest; and then take their 
departure for sunnier climes. Few remain where they 
were horn, singing rarely and softly the songs they sang 
in spring. By far the greater portion emigrate to foreign 
lands, whither they bear their own sweet music. The 
song of the Nightingale passes away with her; its tones 
die away with the flowers till spring comes again, 
bringing them both in its embrace. 
It is plain that such departure and return is interesting 
to man: chained, as he is, to this earth, it is clear that 
where experience is insufficient the power of the imagin¬ 
ation must intervene. It is only lately that we have been 
able to collect the results of reliable observation, though 
insufficient after all. 
The migratory movements of birds may be divided into 
three classes; they are as follows: first, a regular and 
definite passage; secondly, one less defined and regular 
in its character; and thirdly, one which is very arbitrary 
and limited in its extent. The causes for all three alike 
are twofold: dearth of food in their native home, and 
the irresistible desire to migrate, which Nature herself 
has implanted in them. 
The first of these three is a necessity to many birds, 
and is the result of an inborn restlessness developed at 
certain seasons: it takes a definite direction, requires no 
guide, and is annual. No bird of passage is taught this, 
nor is a leader necessary; if the bird is free, love for its 
parents or its partner are the only powers which can in 
any way arrest this longing. On this account we may 
regard the “ passage” as one of the most poetical actions 
