APRIL, 1902. SOME RECENT OBSERVATIONS ON MIGRATION OF BIRDS. 
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Some Recent Observations on the Migration of Birds. 
By H. A. WINKENWERDER, 
( Preliminary Report ) . 
The following paper is designed merely as a report of progress. 
During the fall of 1897 Dr. O. G. Libby called the attention of 
the writer to the excellent facilities the telescope offers for the 
study of bird migration, and during the summer of 1899 upon his 
advice the following work was undertaken. Although it was 
originally intended that the course of investigation should com- 
prise several series of telescopic observations and such material as 
could be obtained from a season's observation at one of the largest 
lighthouses on our Great Lakes, the work has broadened consider- 
ably since then. Since much of value in the study of bird' migra- 
tion depends upon the migratory routes followed in these spring 
and fall flights, some little attention has been paid to this subject. 
Also the history of the study of migration, as well as discussions 
upon the origin and causes of these semi-annual journeys, have 
been included in this work. These phases of the subject are about 
completed, but it will be impracticable to treat them in this article. 
It was intended that the entire work should be completed with 
the present writing, but, owing to the quantity of material col- 
lected and the pressure of other work, this has become impossible. 
Hence the present paper is merely a preliminary report, designed 
to call attention to the progress of the work and the methods of 
procedure. 
Although two visits were made to Spectacle Reef lighthouse, 
near Mackinac, Mich.,* the weather proved unfavorable for the 
collection of data from this source both times. 
TELESCOPIC OBSERVATIONS. 
Telescopic observations were begun at the Washburn Observa- 
tory at Madison, Wisconsin, in the fall of 1899, but the real work 
did not commence until the spring of 1900. During the months of 
April and May of that year five good sets of observations were 
obtained. In the fall of the same year one set was obtained Oc- 
tober 8. During the spring of 1900 interested persons from sev- 
eral of our western universities were asked to co-operate in the 
collection of data, and the result was excellent. The following 
*The writer spent two weeks at Spectacle Reef during the falls of 1 899 and 1900- 
