26 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 





Figure 23. — Mounds on Kavalga Island (July 1937). a and b, undisturbed 

 mounds, c, cross-section of a mound: 1, wind erosion to black soil; 2, 

 vegetation on surface; 3, lava sand 2 1 A incbes; 4, black earth % inch; 

 5, rotted moss 1% inches; 6, black earth % inch; 7, rotted moss 2 inches; 

 8, black earth 1 inch; 9, rotted moss 2V 2 inches; 10, black earth 4V 2 inches; 

 11, rotted moss 12 inches plus. 



to initiate the formation of the so-called bird mounds. Possibly, 

 the creation by the wind of these miniature dunes, together with 

 the perching of birds thereon, are both involved in the formation 

 of these mounds. 



Wind erosion is very severe on some exposures. In places, the 

 wind had eroded the soil in troughs, undermining the vegetative 

 turf to form a crude type of terracing. The woody roots of crow- 

 berry had been exposed and were already supporting a thin coat- 

 ing of lichens. With such constant wind action, one wonders how 

 the vegetation became established in the first place. As shown in 

 part c, wind erosion apparently had affected only the outer layer. 



Marine vegetation is well represented by the kelp beds, which 

 consist of a considerable variety of seaweeds that are prevalent 

 throughout the Aleutian district. The kelp is, of course, the 

 habitat of numerous marine organisms, and during the summer 

 it furnishes a favorite habitat for the sea otter. These kelp beds 

 disappear in the winter. 



The oceanic climate of this region, the high humidity and pre- 

 cipitation, and the prevalence of strong winds have combined to 

 shape the vegetative complex that we find in the Aleutian dis- 

 trict. In turn, this complex, together with climatic conditions, 

 topography, and the rich marine fauna, has influenced the compo- 

 sition of the indigenous fauna. 



