34 TIMES OF MIGRATION 
tree. Food, therefore, rather than temperature is the all important 
factor in a bird’s life at this season. 
February—The conditions prevailing during January will be 
practically unchanged until the latter half of February. Then, should 
there be a period of mild weather, we may expect to hear the Meadow- 
lark, Song Sparrow, and Bluebird, inaugurate the season of song, and 
note the appearance of Robins, Purple Grackles, and Red-winged 
Blackbirds, which pass the winter such a short distance south that 
they appear at the first sign of returning spring. It is probable that 
in most cases the first individuals of our summer resident species to 
arrive remain to nest. (See beyond, under Nesting.) 
March.—While March is certain to witness a general northward 
movement among the birds, the date of their arrival is as uncertain 
as the weather of the month itself. Continued severe weather prevents 
the advance, which a higher temperature as surely occasions. When 
ice leaves the bays, ponds and rivers we may look for Ducks and Geese. 
When successive thaws have made the ground soft enough to probe, 
we may expect the Woodcock. With the advent of insects their enemy 
the Phcebe will appear. ; 
The weather which hastens the arrival of birds from the south, 
also prompts certain of our winter residents to begin their northward 
journey. 
April.—The developments in the plant world, in early April, which 
are apparent to the least observant, are accompanied by corresponding 
but less noticed activities in the world of birds. The migratory move- 
ment now gains strength rapidly and during the latter part of the month 
one may expect new arrivals daily. 
It will be noted that the earlier migrants of the month are largely 
seed-eaters, while those which come later are insectivorous, particularly 
those insect-eaters, which like the Swallows, Swift and Nighthawk 
feed upon the wing. 
May.—As the season advances, marked changes in temperature 
are less likely to occur, and the migration becomes more regular and 
continuous. In February and March there may be two weeks or more 
variation in the times of arrival of the same species in different years; 
in May birds usually arrive within a day or two of a certain date. 
Nevertheless the force of the migratory current is still closely dependent 
on meteorologic conditions, and under the encouragement of high 
temperature may reach the proportions of a ‘wave,’ which when dammed 
by a sudden return of cold weather, floods the woods with migrants. 
Birds are then doubtless more abundant than at any other season. The 
arrival of ten or a dozen species may be noted on the same date, and a 
total of as many as 144 species has been recorded by a single observer 
during one day. (Lynds Jones at Oberlin, O., May 13, 1907.) 
After the middle of the month birds begin to decrease in numbers 
as the transient visitants pass northward, and by the first week in June 
our bird-life is composed of permanent residents and summer residents. 
