ECOLOGY OF ISLE ROYALE. 127 



reason be overlooked. His position is clearly stated (p. 43) as fol- 

 lows : "Owing to the dependence of forms of life on their enviroii- 

 meut, biotic changes are necessarily closely related to environmental 

 changes. These biotic changes may occur in two ways ; the forms must 

 either be able to respond to the new conditions, or be supplemented 

 by other forms. That they tend to become adjusted cannot be ques- 

 tioned, but in many cases at least, this adjustment lags behind the 

 changing conditions, and the forms are replaced by others from ad- 

 jacent habitats which are adjusted to the conditions toward which the 

 particular habitat is cha,nging, thus bringing about a succession of 

 societies." In speaking of the biota of the hard-wood forest he further 

 says: "This region has been reserved for the last, for the conditions 

 are evidently those toward which the 'other habitats tend to be changed 

 under the present conditions. . . .This society thus represents the climax 

 society of the region. It consists of the forms that are adapted to or 

 associated with the conditions which prevail in this region in the last 

 stages of the mutual adjustment of all the environmental processes. 

 As the processes become adjusted to one another, the habitat of the 

 climax society is increased at the expense of the other habitats, and 

 the associated biota tends to become of general geographic extent in 

 the region." 



The only other paper discussing avain succession is that by Frothing 

 ham ('06), and this is not a "natural" succession but one influenced 

 primarily by man. He clearly expresses a bird succession correlated with 

 the reforestation of burned lands. The area studied is the Michigan 

 forest reserve on Higgins Lake. The region was originally covered with 

 White and Norway pine, but repeated flres first killed off the pines, later 

 the oak and maple; and finally the dominant vegetation is sedge, sweet 

 fern, huckleberry and prairie willow. With the fire protection afforded 

 by the reserve, Frothingham anticipates a reversal of the above succes- 

 sion of destruction, and further remarks: "With the types of vegeta- 

 tion which mark the different stages of the plant succession just de- 

 scribed there seem to be correlated certain definite bird forms. These 

 forms are for the miost part such as frequent observations in northern 

 Michigan have identified as generally characteristic of the respective en- 

 vironments." This is followed by lists of birds characteristic of differ- 

 ent kinds of vegetation. While these lists do not correlate perfectly 

 with the implied succession, yet the general statement of the problem 

 i? clearly expressed. 



The burning of forests has long been known to change the character 

 of the vegetation and fauna of areas, but this is often referred to as the 

 change of a "life zone." Thus Merriam {'99, p. 47) states that ai fire 

 in the Canadian zone on Mt. Shasta is followed by the Transition 

 zone and remarks: "But in the meantime a new growth of Shasta 

 fir has started, and in ten or twenty years is likely to overtop and 

 drown out the Transition zone species, enabling the Canadian zone to 

 reclaim the burn .... But on the steeper slopes, especially rock slopes, 

 if the vegetable layer is burned off, the (lower) zone which creeps up 

 to replace the (higher) one destroyed becomes permanent or nearly 

 so ... . Def orestration of an area therefore tends to lower its zone posi- 

 tion." Birds are not mentioned in this discussion nor the relation of 



