18 ^ ILUNOIS BIOLOGICAL MONOGRAPHS [116 



HIGHER VERTEBRATES 



Vertebrates characteristic of aquatic environments were fairly common 

 in most parts of the Big Vermilion River valley. Three species of turtles 

 were observed: the western painted terrapin {Chrysemys cinerea Bonna- 

 terre), the snapping turtle (Chelydra serpentina Linn.) and the soft shelled 

 turtle {Platypeltis spinifera LeSusur). The garter snake (Thamnophis 

 sirtalis Linn.) was observed swimming across the stream in several places. 

 The fox snake (Elaphe vulpinus Baird and Girard) was seen on several 

 occasions near the margin of Salt Fork above St. Joseph. Frogs, among 

 which the pickerel frog (Rana palustris LeConte) was noted, were abun- 

 dant in many places, and tadpoles of all ages were abundant in both the 

 Big Vermilion and Sangamon rivers. 



Aquatic birds were occasionally seen in both river valleys. The little 

 green heron {Ardea virescens Linn.) and the great blue heron (Ardea hero- 

 dias Linn.), as well as the American bittern (Boiaurus lentiginosus Mon- 

 tague) were seen repeatedly, especially in the old river cut-offs between 

 Urbana and St. Joseph. Where high banks occur the kingfisher {Ceryle 

 alcyon Linn.) made the woods resound with its rattle-like notes. These 

 birds feed largely on young fish and in this way affect the mussel distribm- 

 tion by reducing the number of fish that may bear glochidia. Shore birds, 

 among which were noted Wilson's snipe {Gallinago delicata Ord.), solitary 

 sandpiper {Helodromus solitarius Wilson), yellowlegs (Totanus), sora rail 

 {Porzana Carolina Linn.), and killdeer (Oxyechus vociferus Lion.). The 

 pied-billed grebe (Fodilymbus podiceps Linn.) is seen frequently during 

 spring and autumn on Crystal Lake and in the more pond-like reaches of 

 the Salt Fork. Many of the shore birds feed on moUusks and insects which 

 they find along the shores of the Big Vermilion River system. During 

 migrations, the river valley and its tributaries are fairly alive with birds of 

 all kinds, and at such times the region is well adapted for bird study. 



The presence of the muskrat {Ondatra zibethica Linn.) is attested by 

 the number of piles of opened mussel shells, the animals of which have 

 provided this mammal with many a meal. In these muskrat piles have 

 been found the shells of many species that are rare or difficult to find alive 

 in the streams. 



The abundance of all groups of animal life in the Big Vermilion system 

 indicates that it is a favorable environment for an optimum biota. With 

 the exception of the upper twenty miles more or less seriously affected by 

 sewage pollution, the stream is one of the best collecting grounds in the 

 State, a condition indicated by the very large mussel fauna of thirty-eight 

 species and races, recorded in the following pages. 



FISH PAUNA OF THE BIG VERMILION RIVER 



The close relationship between the mussel fauna and the fish fauna, 

 through the breeding habits of the former, render a knowledge of the fish 



