18 ILLINOIS 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 (Botaurus 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 distribu- 
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 Linn.). The 
pied-billed grebe (Podilymbus 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 mollusks 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 FAUNA 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 
