122 MICHIGAN SURVEY, 1908. 



marked influence upon the practical field studies of the bird student. 

 It should lead to a more intelligent understanding of the relation of 

 birds to the world about them, or even better, to the world of which 

 they form a part. 



Attention should further be directed to the fact that simply the 

 occurrence of the bird in a definite habitat is not by any means the 

 sole aim of such work. The influence of the environment should be 

 studied in its bearing upon all phases of bird life. Not only should 

 the most favorable habitat or optimum) be recognized, but also the in- 

 fluence of the less favorable conditions; thus the nesting site, composi- 

 tion of the nest material, food, abundance, feeding grounds, migrating 

 habits and all like relations are needed for an adequate and exhaustive 

 study of the ecological distribution and succession of birds. 



It is therefore not surprising that such requirements will be diflS- 

 cult to. meet because the facts themselves are diflBcult to secure. Thea 

 there are further diificulties which are due to the limitations of the 

 student himself, and are psychological in their natui-e. As examples of 

 this class of difficulties two may be cited, because they are of frequent 

 occurrence in all kinds of scientiflc work and not by any means confined 

 to the study of birds. For, contrary to our youthful ideas, naturalists 

 have the same limitations as humanity in general ! We may divide 

 naturalists into two classes, depending upon their primary type of mind. 

 First, those who tend to see only the infinite detail of isolated facts and 

 observations. This type of mind is particularly impressed with the 

 multiplicity and variety in nature, and is one to which a general state- 

 ment is almost a cause of irritation because there are usually exceptions 

 to any general statement. The consti'uctive imagination seems feebly 

 developed in this type. To this class belongs many extremely valuable 

 and useful students, because of the data which they, often with extreme 

 conscientiousness, collect. They are collectors of facts rather than stud- 

 ents of relations. To the second class belongs that type of mind whose 

 primary interest is in generalizations, principles, relations, and which 

 tends to neglect isolated facts and observations. The constructive im- 

 agination is liable to be developed in this type. This includes many 

 extremely valuable and useful students on account of their tendency to 

 condense, sift and formulate great masses of isolated facts. They ai*e 

 students of ideas and relations rather than collectors of "facts." 



Each class, especially the well-marked types and extremes, often finds 

 it difBcult or impossible to understand the point of view of the other 

 class. This frequently leads to misunderstandings and often to mutual 

 contempt. Cope and Marsh clearly illustrate these two types of minds- 

 among our American naturalists. 



By this time some may Avonder why this subject has been introduced. 

 It has been with a definite purpose, because frequently these opposed 

 points of view cause delays in the development of many subjects. Thus 

 a forewarning to students of bird ecology may produce good results if 

 the individual student makes a conscious effort to counterbalance such 

 deficiencies as go with his particular type of mind. In the past, details 

 have tended to produce confusion through the neglect of general ideas. 

 It is rarely that a word of warning on this subject is out of place, be- 

 cause the balanced "golden mean" investigator is never too abundant. 



