26 
as a basis of comparison, but also to serve as a model for observers in 
future years. 
The expression “bird wave” has been used many times. The term 
is capable of two interpretations; consequently, two methods of, study 
are possible. 
(1) A “bird wave” may be considered to consist of a very large num- 
ber of individuals, of one or many species, which suddenly invade a 
certain area. In studying such a wave it is necessary to ascertain the 
species of which it is composed gnd the boundaries of the area over 
which it extends. : 
(2) Certain species, known to be migrating in company on a given 
day, may be considered to constitute a “‘ wave,” and their progress may 
be watched from day to day and from week to week. 
This latter mode of study is applicable to the earliest waves only, for 
it is only early in the season, if at all, that the same species which are 
together in the south keep together during the entire journey. In all 
the later waves the species migrating in company change from day 
to day. Hence no attempt will be made to follow waves of this char- 
acter; and the first, or bird waves proper, will alone be dealt with. 
It is usually believed that all birds reach their winter quarters by 
the end of December, but in this respect the winter of 1883-84 was 
exceptional. The fall of 1883 was very warm, and from latitude 39° 
southward there was no cold weather before Christmas. About this 
time, however, the real winter set in, and by January 2 it had extended 
southward to latitude 33°. Hence, fall migration did not end until the 
first week in January; and since spring migration began in central 
Mississippi on January 11, but little time was left between the end of 
the southward and beginning of the northward movement. It is to be 
observed, however, that the southward movement of January 1 was con- 
fined chiefly to the Thrush and Sparrow families, while the northward 
movement consisted wholly of water-birds. As examples of this late 
staying of birds at the north the following may be selected: Dr. G.S. 
Agersborg reported from Vermillion, Dak. (latitude 42° 56’), that ‘in 
early January birds were few, probably owing to previous mild weather. 
On January 5 winter set in, with the thermometer at 343° below zero, 
and by the end of the month all our winter residents were here except 
the Bohemian Waxwing, the Evening Grosbeak, and the Magpie. Pur- 
ple Grakles and Cowbirds did not leave until December 26, a later date 
by twenty-seven days than any noted since 1867, when I commenced 
to record arrivals and departures.” 
At Saint Louis, Mo. (lat. 38° 40’), the cold spellset in with a snow- 
storm January 1, causing most of the Bluebirds, Shrikes, Red-tailed 
Hawks, Red-shouldered Hawks, and Gulls to retreat southward, and 
bringing down large numbers of Crows. ' 
From Anna, Ill. (lat. 37° 30’), C. W. Butler reported: “Until Janu- 
ary 2, I could pick strawberry blossoms growing out of doors and 
