Density of bird population.—In June, July, and August, 1907, a special survey was made under the direction of Pro fessor S. A. Forbes to determine the abundance of birds in Illinois. Two observers traversed 428 miles in the southern, central, and northern parts of the state. They counted all the species and all the individuals on a total area of 7,693 acres. They found 85 species and 7,740 individuals. This gives a density of 645 birds per square mile, or almost precisely 1 bird per acre. On this basis, Illinois contained 36,000,000 birds. The English sparrow was the most numerous, making up 7S per cent of the individuals observed; the meadow lark consti tuted 13 per cent ; the bronzed grackle 11 per cent; the mourn ing dove 6 per cent; and the dickcissel 5 per cent. Others, constituting more than 1 per cent, and in order of abundance, were: red-winged blackbird, prairie horned lark, flicker, robin, field sparrow, American goldfinch, kingbird, bobolink, grass hopper sparrow, brown thrasher, cowbird, red-headed wood pecker, barn swallow, quail, Bartramian sandpiper, and crow. These 21 species included S5 per cent of the individuals observed.
The English sparrow decreases in abundance from north to south. The meadow lark increases in abundance from north to south as does the total of bird life. For every 100 birds counted in northern Illinois, 133 were found in central Illinois and 1S1 in southern Illinois. These Illinois birds showed a decided preference for prairie and woodland conditions. Fifty per cent of the birds were found in pastures and meadows which constituted only 36 per cent of the land surveyed. Birds were about one-third as abundant in cornfields as in grasslands; and in small grains they were twice as abundant as in corn. In orchards they averaged 41 times as numerous as in fields of grain, 2,471 to the square mile. Among native trees and shrubbery the density of birds averaged 1,451 per square mile.
Reptiles and batrachians.—Reptiles include snakes, lizards, and turtles; batrachians include mud-puppies, salamanders, toads, and frogs. Natural conditions in Illinois were favorable for the development of a varied and somewhat abundant life of reptiles and batrachians. The march of the white man, however, has made the existence of these forms of life more difficult than formerly. The poisonous rattlesnake, once abundant, has been nearly exterminated. Garter snakes, bull snakes, moccasins, grass snakes, and blue racers are com mon in Illinois at the present time. Turtles are common, especially along the Illinois river, and they are of commercial importance; $15,000 worth have been marketed in a single year. The extensive drainage of swamps has greatly reduced the number of frogs of the state.
Fishes of Illinois.—The entire fish life of Illinois comprises 150 species. A comprehensive study of them has been pub lished by the Natural History Survey of the state.
About three dozen of our 150 species of Illinois fishes have a marketable value as food, and a dozen more may be classed as edible, although not popular enough or abundant enough within our limits to have any com mercial value as Illinois products. A dozen of the more useful species are of really good quality, and half of these are among the best of the fresh-water species. In the following list the edible species are distinguished in classes of graduated importance, according to our judgment of the estimation in which these fishes are generally held. A few species are put in a lower class than their quality would call for because of their infrequent occurrence in our fisheries.
First class.—Whitefish, Great Lake trout, blue cat, channel-cat, mud cat, common pike, white crappie, black crappie, bluegill, small-mouthed black bass, large-mouthed black bass, wall-eyed pike.
Seco,ed class.—Golden shad (rare), northern mooneye (rare), lake herring, eel, Missouri sucker, red-mouth buffalo, mongrel buffalo, small mouth buffalo, European carp, eel cat (rare), lake catfish (rare), rock bass, blue-spotted sunfish, long-eared sunfish, pumpkinseed sand-pike, yellow perch, white bass, yellow bass.
Third class.—Paddle-fish, lake sturgeon, shovel-nosed sturgeon, white nosed sucker,_ common red-horse, short-headed red-horse, yellow bullhead, common bullhead, black bullhead, little pickerel, warmouth, sheepshead.
Fourth class.—Dogfish, gizzard-shad, river carp, lake carp, spotted sucker, common sucker, burbot.
The distinction of Illinois as a fish-producing state is to be found in its relation to the Mississippi River and some of the most important branches of that stream. The state is traversed diagonally by the Illinois River, admirably adapted by its sluggish current, by the many bottom-land lakes connected with it at low water, by the extensive afforded to fishes during the period of the spring overflow, and by the vast abundance of fish food in its waters at all seasons of the year, to support an unusually large and varied fish population.
Illinois markets a larger value per annum in fishes taken from flowing streams than all the states immediately surrounding it taken together. Illinois furnishes, indeed, more than one-third of the fishes sent to market from all the streams of the Mississippi Valley. Furthermore, Illinois River and its tributaries produced, in 1S99, 72 per cent of all the fishes taken from the streams of the state, and a fourth of the entire fish product of the Mis sissippi Valley came in that year from this one stream. The totals for the different Illinois stream systems were as follows: Illinois, 8371,110; Mis sissippi, $118,278; Wabash, 838,065; Ohio, $20,029; Kaskaskia, $3,002; Big Muddy, $1,136.