. and go silently and unawares.’ No one sees the wren or the sp 
, 
* 
uncommon bird in northern New Jersey during fall, is è 
“ingly rare in spring; while, on the other hand, the Blackburnian 
340 THE MIGRATION OF BIRDS. 
distant specks against the sky, are seen floating slowly south 
after their departing prey. But the vast majority of birds co 
row on its migration; no one knows how long, they are on í 
way, or by what route they reach their destination. We know — 
that they come from the south in the spring and return in the fall, — 
and there our knowledge ends. 
Most birds move north and south in their migrations; but ab 
though this is the general direction of the movement, it is aff 
more or less by various circumstances. On the seaboard, it 
“follows the general course of the coast, and in the west it is i 
enced by the border line between the prairies and the forests 
which, throughout Minnesota and Wisconsin, lies in a northw 
and southeast course. Mountain ranges and the interior lakes 
alter: the general north and south direction more or less, an 
isothermal lines point out other variations. Some birds appeat 
to follow different routes on the autumnal migration from 
which they take on the vernal. The Connecticut warbler, & 
warbler is far more abundant in spring than in fall. Other 
again, appear to take a fancy to some particular line of flight, al 
adhere to it for a number of years, then deserting it for some 97 
I have known the golden plover, for instance, to be quite abun® 
spring, on arriving at the mouth of the Minnesota, Soph” 
follow up one valley and sometimes the other ; one of the two” 
variably attracting by far the larger proportion, though wi? 
any apparent reason. ee 
The regularity which marks the arrival and departure of Ei 
birds is quite remarkable. For five successive years, I wie 
first coming of the crow and red-winged blackbirds on the e 
February, and so punctual were they, that at last I came to 
them almost as certainly on that day, as though they had y 
company of players, announced to appear at a certain time 
arrival was a day or two later or earlier. Between the m 
19th of October, I expected tọ see the southward fight 
