GEORGRAPHY OF BIRD STUDY. 67 
with the lowest showing on the map, only 7 have over 1000 
Juniors in 1921; only one of the latter (Nebraska) has over 
2000 and the average of the 18 is about 900. For 15 states 
having 3 of more local clubs, the average is over 8000, only 
one (Maine) having less than 4000. 
The reasons for such distribution seem to be several, and 
to relate to both bird and human population. The following 
list may be useful as a basis for study: 
1. People—number, character and. education. 
2. Birds—number, whether resident or migratory. 
3. Environment—topography, plants, climate. 
These conditions are rather complex, one often affecting 
one or more of the others. Density of population is probably 
more important than any other single one, since only a cer- 
tain number of people may be expected to be naturally in- 
terested in birds. This proportion increases to a certain extent 
with education and may also vary in-different sections ac- 
cording to the character of the population. Comparing the 
map of density of population (Literary Digest for Oct. 29, 
1921) with the one here presented, a fairly close agreement is 
noted. Bird study runs lower in the south-eastern states 
except Florida where it is higher. It is high also in Indiana, 
Michigan, etc. These differences can probably be accounted 
for by character of population. 
As to number of birds, migration plays a prominent part. 
Of the 1200 kinds of birds found in the United States and 
Canada, one-fourth or more may be seen in a single state. The 
phenomenon of migration makes one of the strongest appeals 
to the mind of man but it is to the majority of people of more 
temporary interest than the study of nesting habits. Thus 
while migration adds very greatly indeed to interest in birds, 
the matter of summer residence probably offers the strongest 
permanent interest. The counts thus far made have indicated 
a higher number of summer residents for the eastern states. 
The character of the country has important influences of 
-many kinds. Lack of trees and especially of thickets reduces 
the number of tree nesting species. A country of varied to- 
pography will have many kinds of birds as there will be ponds 
for water birds, meadow or prairie for ground dwellers, tall 
