68 THE AMERICAN MIDLAND NATURALIST 
trees, bushes, bank, cliffs or caves for their respective kinds. 
Such country offers also a greater variety of plants, insects 
end other animals which furnish food supplies. Trees, while 
desireble, have liv itations. A dense forest, especially, is com- 
pesed of only a few kinds of trees, offers only a limited range 
cf conditions and m2iyv be as barren of birds as the treeless 
plain. Fortunately the effect of such conditions often is re- 
lieved by proximity of arcas of different type. 
Climate is important as determining the distribution of 
birds. It controls their study as well to a considerable extent. 
The majority of people interested in birds are those who are 
drawn afield by pleasent weather rather than those who are 
out regardless of the temperature and moisture. The northern 
plains in winter or the southern plain in summer offer con- 
ditions which are favorable to neither bird nor student. 
Changes in population affect also the bird population. This 
greatly decreases the numbers of certain species (indeed we 
regret that it has even caused complete extinction of some), 
but has the opposite effect on others. With an even moderate 
protection any locality should retain an interesting bird life. 
The writer has felt that often the greatest need of bird study 
is for people with natural ability to direct the work. With 
less capable leaders much more time and energy must be used. 
This suggests that it is desirable to try especially to interest 
those who show such ability in other work. 
