OCTOBER, 1902. 
THE MIGRATION OF BIRDS. 
199 
long at one stretch. It is, therefore, advisable to have two observers so as 
to relieve each other every half hour or even every fifteen minutes, the 
one writing the observations while the other is observing). 
The time should be divided into periods of fifteen minutes each, i. e., 
the observations should be made for periods of this length. 
The following data should be noted wit., every bird that crosses the 
field of vision: 
The number and approximate tenths (as indicated by the hair-lines) at 
which the bird enters and likewise at which it le-aves the field of vision. 
The speed at which it is flying — slow, fast, like a shot, etc., etc. 
His approximate size as compared to Goldfinch (size 1), Robin (size 
2), and Crow (size 3). If slightly smaller add — sign, if larger a -[- sign. 
State if the bird is out of focus. 
State if its wing-strokes are plainly seen. 
Other remarks that you may think of value. 
The notes should look like this : 
Madison, Wis., May 14, 1900. Warm, with quite strong southwest 
wind; sky perfectly clear. 
Period, 
8:15—8 
:30. 
I. 
II 
III. 
IV. 
In. 
Out. 
Speed. 
Size. 
4.d 
1.2 
very slow 
2 
3.8 
8.1 
fast 
1 
3.8 
8.1 
fast 
1 
5.2 
8.8 
very fast 
1 
4.1 
" 8.5 
fast 
2 
Remarks. 
Small hawk soaring. 
Flight like goldfinch. 
Flight like golafinch. 
Curved below center. 
III. and IV. are of less importance than I. and II. 
These instructions resulted in eight excellent sets of data, and 
much credit is due Mr. Leon J. Cole of Ann Arbor, Faculty Uni- 
versity of Michigan ; Mr. H. S. Warren, of Detroit, Secretary 
Michigan Ornithological Society; Mr. William James Rice, Fac- 
ulty Lake Forest University ; Mr. O. S. Dart, student University 
of Minnesota, and Mr. Wegemann, student Beloit College, and 
their assistants, for their hearty co-operation in the collection of 
these data. A set consisting of one evening's observations was 
contributed from each of the following places : Ann Arbor, De- 
