VOL. VIII.] A STUDY OF BIRD (ECOLOGY. 185 



a vast number of circumstances ; we must inquire into 

 its food and nesting requirements, into its comparative 

 abundance in different types of country, different 

 climates, and different latitudes : into the extent of its 

 daily movements as well as the extent and even the 

 causes of its migration. Indeed, in a sense, cecology 

 includes the whole life of a bird ; for to understand the 

 relation of a bird to its environment we must know 

 not only everything about the environment but also 

 everything about the bird. The only essential differ- 

 ence between the oecological study and any other study 

 of birds is in the aim of the student. 



The whole science, therefore, will not be compassed, 

 even for any one species of bird (indeed, no species can 

 be isolated from its fellows), in a short time. But it is 

 on this account all the more worth while to consider 

 by what methods of study we may expect to arrive 

 at the most satisfactory results. So many ornithologists 

 have provided exact information on the nesting-habits 

 of birds, including the position and structure of the 

 nest, the number of eggs and the proportion hatched 

 and reared in different parts of the range of each bird, 

 the amount and kind of food brought by the parents, 

 and all the circumstances of family life, that I do not 

 propose to refer to this side of cecology at all. In some 

 ways it is the easiest part of the study ; certainly it 

 has been more adequately treated than any other part. 



Very little, however, is known of what I might 

 call the minutiae of bird-distribution and migration. 

 We know, roughly — less roughly than a generation ago — 

 the geographical hmits of each species and the routes 

 by which it travels from and to its breeding-quarters. 

 A vast amount of exact information must still be dis- 

 covered, however, before we can hope to understand 

 the meaning of these things. In this country, for 

 instance, we may set to work to discover whether each 

 of our species is increasing or decreasing — such as the 

 Land-Rail — hoping, as we pursue our investigations, 



