OCTOBER, 1902. 
THE MIGRATION OF BIRDS. 
203 
elusion that these birds were following migratory routes of lesser 
importance. 
A feature of special note in Plate VIII., showing the direc- 
tions of flight at Madison, is that there are two general directions 
followed here. From the preceding discussion, in which it was 
found that physiographic features are followed very closely, we 
might infer that the peculiar lake topography about Madison has 
brought about these two general directions. 
It is, however, noteworthy in the plate that of th^se two direc- 
tions one predominates in April and the other in May, though the 
percentage of the May-flight, if we may refer to it by that name, 
is not as marked over the April-flight in May as in the latter over 
the May-flight in April. Of the more common migratory species 
of this region something over 70 per cent of those that arrive here 
in April, and perhaps the first few days in May, are summer resi- 
dents. Of those that arrive after that time about 60 per cent are 
mere migrants for this region ; that is, they pass through here to 
breed farther north. Since these figures are only rough estimates, 
and furthermore would need to be modified considerably by the 
abundance of the number of individuals in the species, we can only 
hint at a possible interesting line of investigation that suggests 
itself here. It may be objected that this consideration is at pres- 
ent too vague even to allow of suggestion. However, if we take 
the list of one hundred species, with the dates of arrival and de- 
parture, prepared by Mr. F. M. Chapman (43), it will be seen 
that the percentages given above have not been overestimated in 
favor of the principle to be involved (44). About 64 of these 100 
species arrive here before the end of the first week in May, and 36 
after that date. Of the former, 52, or 81 >4 per cent, are summer 
residents ; of the latter, onlv 14, or about 38 8-10 per cent, are sum- 
mer residents, the remainder breeding farther north. Moreover, 
the proportion of the number of individuals in those species that 
arrive here in May and are summer residents is in all but a few 
cases far below those that merely pass through here. Of fourteen 
summer residents that arrive here in Mav about ei^ht are gener- 
allv included among the rarer species, while only six are abund- 
antly found, which would seem to show that in all probabilitv the 
greater number of birds that flv through Madison in Mav breed 
farther north, and hence that different routes are followed by the 
two groups of birds. 
43. Handbook of Birds of East. N. A.. K". Y., 1897. pp. 15-17. 
44. This list has been slightly modified by notes taken in Wisconsin in 
recent years. 
