OCTOBER, 1902. 
THE MIGRATION OF BIRDS. 
209 
Although Dr. Brewster has not found it so at Point Lepreaux, 
telescopic observations tend to show that certain individuals may 
be collected into fairly compact flocks, numbering from a few to 
a large number. Thus in the data collected at Beloit, May 12, 
1900, from 1:45 to 3:00 A. ^i., there are five records (see ap- 
pendix, pages 238 to 240) where birds appeared in comparatively 
large numbers, in such rapid succession — often a number in the 
field at the same time — that it leaves little room for doubting that 
these birds did belong to fairly compact flocks. To say that in 
some instances as many as ten or more birds crossed the field 
in less than one-third that many seconds would not be an over- 
statement of the case. Moreover, the actual number recorded 
must have been only a small number of all that were associated 
in one flock. In fact data obtained by listening for bird calls on 
dark nights seem to indicate that it is not an uncommon occurrence 
for nocturnal migrants to fly in fairly compact flocks. 
That flocks and single individuals flying side by side, are mov- 
ing independent of one another is evident from the range of speed 
exhibited. Throughout the observations it was common to see 
birds, at times, apparently side by side, flying at rates that varied, 
from the extremely slow to the very highest rate of speed. On 
the other hand it is quite obvious that the general movement of the 
stream may have a guiding influence to such birds as have had 
little or no experience. 
Although it is only in rare instances that species can be identi- 
fied, the general outline, the size and the motion of the birds as 
they are seen silhouetted against the moon leaves little doubt 
to the observer that he has a diversity of species passing through 
the field of vision. The large number of routes that lead to the 
more important highways would bring individuals from diverse 
regions together along these courses. On the other hand, birds 
that become associated do not necessarily continue thus to the 
end of their journey. Dr. Brewster makes the following state- 
ment in this connection : "During even its earliest stages their 
members must become separated from one another and become 
associated with birds of the same or different species belonging 
to other flocks which may have started from various localities, 
but which are traveling in the same direction and along the same 
or parallel paths" (52). 
As to how these birds separate again. Dr. Brewster says : ''An 
answer to this question was suggested at Point Lepreaux by the 
52. Brewster. Mem. Nutt. Ornith. Club, Xo. 1. 1885, p. 13. 
