18 ETON NATURE-STUDY 



birds of which all the individuals disappear at one time of the year 

 or another. 



The practice in observation will be considerable, and the interest 

 to the student equally great. The knowledge acquired, however, 

 will probably not include any facts hitherto unknown, and if the 

 pursuit is in the end adopted as a hobby, something in the way of 

 original investigation will be sought for. This can be found in 

 another branch of the subject, to wit : that which deals with 

 species of birds of which only the majority of the members vanish, 

 a few being always present. In this direction there is much still to 

 be discovered. 



Such partial migrants as the pied wagtail, the songthrush, and 

 the red-breast would certainly repay the closest watching. We are 

 still ignorant of many of the causes which determine the presence of 

 these birds in varying numbers in particular spots during different 

 seasons of the year. Careful observations made in different parts of 

 the country, as to the relative number of partial migrants in each 

 month, and a co-related table of the conditions as to climate, food 

 supply, presence or absence of special enemies, would therefore be of 

 the greatest use. To do this would certainly be a more difficult task 

 than the making of such a calendar as has been given above ; yet a 

 few notes taken daily by the nature student on the lines suggested, 

 would, at the end of a series of years, furnish valuable data for the 

 agriculturalist, the bird protector, and the expert naturalist to work 

 upon. 



When we see how dependent all forms of life are upon one 

 another, and how keen is the struggle for existence among 

 individuals of the same and allied species, it is obvious that the 

 causes which led to the present forms of living things must be looked 

 for in the relations of animals and plants to their surroundings. 



