Introduction. 
75 
conclude this partly from my acquaintance with the “Great 
Wood,” spoken of later, partly and principally from the experi 
ence that the largest flocks are seen most often in the above 
named peninsula towards evening or during the afternoon. 
That Ihe migration of warblers takes place during the night 
is, I think, indubitable. When they were seen on the peninsula 
towards evening it seems highly probable that they arrived at 
the stopping point a little south of Shiocton in the morning, 
and that they slowly moved about in the course of the day in 
search of food. Perhaps only under certain conditions the newly 
arrived flock reached as far as the peninsula. On many warm, 
still days the birds were seen only scattered and singly. When 
a large flock was seen in the afternoon, it was usually bad 
weather—rain or high wind. On such days the birds were 
very restless. The flocks hurried from tree to tree. If the 
wind became a storm they were unable to continue migra¬ 
tion. They sat dishevelled and disheartened in bushes and 
brush or even on the ground. If the storm continued several 
days, hosts of birds were seen from morning till evening. That 
was merely testimony that the migration was arrested. I think 
for this reason that one should by no means conclude that the 
greatest migration corresponds to the time when one sees the 
most birds in a day. The migration is certainly for the most 
part unobserved. Most of the flocks go over the observer’s 
head while he sleeps. It is therefore largely accidental what 
birds he sees. I suppose however, that after a heavy migration 
there are almost always scattered individuals to be seen that for 
some reason have become separated from the flocks. In this way I 
explain the appearance of single individuals of Sylvania pusilla. 
If this be true the observations have still some value. I have 
sought to give in a list — even if very incomplete — an idea of 
the numbers of the different warblers seen. It cost me much 
labor, but I consider it no longer of much value now that I have 
come to see the conditions under which the observations were 
made. Many of the gray-green warblers (such as Dendroica 
palmarum , D. vigorsii and Helminthophila celata ) were probably 
seen oftener than is specified; but they are not easy to identify 
at a distance, and I was unwilling to shoot a large number. 
