ECOLOGY OF ISLE ROYALE. 121 



THE ECOLOGICAL SUCCESSION OF BIRDS.* 



BY CHARLES C. ADAMS. 



"Of all truths relating to phenomena, the most valuable to us are those which 

 relate to their order of succession. On a knowledge of these is founded every 

 'reasonable anticipation of future facts, and whatever power we possess of in- 

 fluencing those facts to our advanta-ge." — Joha' Stuakt Mill. 



"Indeed, some geologists seem to take pride in lack of knowledge of principles 

 and of their failure to explain the facts observed "in the terms of the elementary- 

 sciences. I have heard a man say: 'I observe the facts as I find them, unpreju- 

 diced by any theory.' I regard this statement as not only condemning the work 

 of the man, but the position as an impossible one. ...The geologist must select 

 the facts which he regards of sufficient note to record and describe. But such 

 selection implies theories of their importance and significance. In a given case 

 the problem is therefore reduced to selecting the facts for record, with a broad 

 and deep comprehension of the principles involved, a definite understanding of 

 the rules of the game, and appreciation of what is probable and what is not prob- 

 able; or else making mere random observations. All agree that the latter alter- 

 native is worse than useless, and therefore the only training which can make 

 a geologist safe, even in his observations, is to equip him with such a knowledge 

 of the principles concerned as will make his observations of value." — Pbesidekt 

 C. R. Van Hise. 



I. Introduction. 



Almost every observer of animals has noted that certain kinds of 

 birds are usually found associated in certain conditions, as, for ex- 

 ample particular species of sandpipers and plovers upon the sandy 

 beach, or the Meadowlark and Dickcissel upon certain prairies; but 

 this is rarely considered a subject worthy of serious scientific study. 

 To discuss the significance and value of such ecological study and sug- 

 gest phases for investigation is the object of this paper. By the ecologi- 

 cal distribution of birds is meant that correlation between environ- 

 mental conditions and the occurrence and association of certain species 

 of birds. In such study special attention must be devoted to the places 

 of breeding; nevertheless the associations of birds at all seasons of the 

 year are of importance. It is not the isolated occurrence of these 

 species, but their relative abundance, the association of certain species, 

 and their persistent occurrence in such conditions which is signifi- 

 cant. In the literature of ornithology there is a vast amount of isolated 

 data bearing on this subject, but very little of it has been organized 

 and systematically studied. 



When once the facts and general ecological relations have been de- 

 terjuined, so that the representative bird associations or societies of 

 given localities have been correlated with their proper environ- 

 ments it will then be possible to determine how one society becomes 

 transformed into another, whether this is due primarily to other birds 

 or to other environmental influences. A knowledge of the succession 

 of bird societies and of the laws of changfe will not only lead to new 

 ideas as to the influence of the environment, but will also have a 



* Reprinted, with the addition of chapter VI, from tlie Aulc, 25, pp. 109-153, 1908. 

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