% 
104 Bulletin Wisconsin Natural History Society. [Vol. 10, Nos. 1 & 2. 
passing Northwards in the direction of Neenah. As dusk was 
coming on, the midges were beginning to fly in larger numbers, 
as is commonly true of these insects, so that it seemed unnecessary 
from my standpoint that the flocks of birds should move further 
north. At this season of the year when flocks tend Southwards, I 
cannot but correlate a Northward trend with a sudden appearance 
of midges from the lake attracting all birds towards such fortui¬ 
tous and phenomenal feeding ground. In the midge article 
referred to above, climatic reasons for the sudden appearance of 
the enormous numbers of this midge are dwelt on in detail. 
Can it be possible that the reason for so many of these birds 
which normally appear in flocks at this time of year, making their 
gathering foci about marshes and lakes, is due to this very abund¬ 
ant emergence of this midge or other insect life inhabiting wet 
places and maturing in August or September? If so, the disap¬ 
pearance of such abundant food in these marshes would certainly 
urge the gathering flocks Southward to later maturing broods of 
similar insects in like abundance long before all food has disap¬ 
peared in the coming on of the winter’s cold in Wisconisn. This 
would then be another factor in the migration period favoring the 
food scarcity idea. It does not argue, however, that the birds are 
forced Southward by an entire lack of their normal food, but that 
the failure of some superabundant favorite food species is the 
cause for the Southward movement. This relieves observers of 
the need of proving that all favorite foods are gone in watching 
for the cause of migrations of each species. It is to be under¬ 
stood, of course, that the sudden appearance of such excessive 
midge swarms is followed within a week by their sudden demise, 
due to the particular species having passed its normal span of 
life. If this be true, have we not the right sort of answer as to 
why the birds know enough to start even before cold weather 
sets in? 
In the same way, it might be shown that the superabundance 
of insect life reappearing from hibernation in the spring, causes 
the birds’ return Northward. By this, I do not mean that there 
are necessarily any more insects in the regions Northward emerg¬ 
ing from their winter sleep, but that there may be greater abund¬ 
ance of species highly delectable to each particular species as is 
shown by the difference in date of migration of the different bird 
