228 On the trail of vanishing birds 



vireos, Tennessee warblers, three-toed woodpeckers are not pres- 

 ent, but are close at hand and sometimes may be seen or, at least, 

 heard in the distance. The same applies to tamarack-spruce species, 

 although these nearly overlap the birds of the crane ponds, with 

 interesting variations. Actually the region is one of very small 

 shallow ponds with bottoms that are soft and boggy, but with 

 sedge, bulrush, spike rush, and muskgrass growing along their 

 borders, and cattails here and there. In this they differ from ponds 

 of a typical muskeg region. The higher ground between the ponds 

 is covered by thickets of mixed birch, willows, stunted black 

 spruce, and tamarack. If there is any plant succession that can be 

 noted it is probably toward a black spruce-tamarack association, 

 although white spruce takes over on the higher ground not far 

 distant. However, one has the impression that plant succession in 

 this area has been arrested, delayed, put off in some manner. We 

 are told that this portion of the Athabaska-Slave River drainage 

 basin was covered by the Keewatin Glacier, and the present flora, 

 of course, has developed since then, a slow, plodding development, 

 probably still incomplete because of the short growing season and 

 the slowness of decay in this latitude. 



The limestone escarpments running across the Alberta Plateau, 

 of which this region is a part, are of Paleozoic age. Raup described 

 four planes of elevation within Wood Buffalo Park, of which the 

 third seems to apply to the pond region occupied by the cranes: 

 a lower plain at about the 800-foot contour; level, but with oc- 

 casional rolling areas and morainic hills, poorly drained clayey 

 soils, and small ponds. A map of the park prepared by Dewey 

 Soper in 1939 shows an elevation of 925 feet near the upper Sass 

 River, and 780 feet to 640 feet along the final escarpment west of 

 the Little Buffalo River, near Lobstick Creek. Farther down the 

 course of the little Buffalo this elevation drops to 545 feet, be- 

 tween the Klewi and the Nyarling. It is 681 feet near the mouth 

 of the Sass, and 495 feet at Great Slave Lake. Thus, although the 

 Sass River drainage, by way of the Little Buffalo, drops some 430 

 feet within a relatively short distance to the level of Great Slave 

 Lake, adjacent pockets such as those within which the crane ponds 



