The Numbers and Local Distribution in Summer of Illinois Land Birds of the Open Country STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION NATURAL HISTORY SURVEY DIVISION STEPHEN A. FORBES, Chief Vol. XIV. BULLETIN Article VI. The Numbers and Local Distribution in Summer of Illinois Land Birds of the Open Country BY STEPHEN A. FORBES and ALFRED 0. GROSS PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS April, 1922 ST A TE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION W. H. H. MILLER, Director BOARD OF NATURAL RESOURCES AND CONSERVATION W . H . H. MILLER, Chairman WILLIAM TRELEASE, Biology JOHN M. COULTER, Forestry ROLLIN D. SALISBURY, Geology WILLIAl\I A. NOYES, Chemistry JOHN w. ALVORD, Engineering KENDRIC C. BABCOCK, Representi ng the President of the University of Illi­ nois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. FoRnES, Chief SCHNEPP & BARNES, PRINTERS SPRIN GFIELD, I'LL. 1 922 62354-1200 ARTICLE VI.-The Numbers and Local Distribution in Summer of Illinois Land Birds of the Open Country. BY STEPHEN A. FORBES AND ALFRED 0. GROSS. In 1913 the senior author of this paper published the product of a statistical study of the midsummer birds of Illinois,* based on a part of the data collected by the junior author in the summer of 1907 by methods already repeatedly described, and of that paper the present one is to be taken as a revision and continuation. The data of 1907 were derived from 7693.5 acres ( almost all in farms) traversed in 428 miles of travel on foot, of which 41 per cent. was in northern, 26 per cent. in central, and 33 per cent. in southern Illinois. The fact that only tentative general conclusions could be drawn from a single year's study was clearly recognized in the beginning, as is shown by the following state­ ment in a first paper on the general subjectt: "The circumstance that the data of this paper are summarized in numerical tables must not be permitted to obscure the fact that they merely present a fixed picture of a fleeting condition; that they are to be taken only as numerical generalizations of the observations here recorded, and do not, in themselves, warrant much by way of inference beyond their immediate contents * * *. Definite conclusions of permanent value concerning the numbers and signifi­ cance of the bird life of the state evidently can not be drawn until many such pictures as these have been assembled, compared, and adjusted in their right relations." It was hence particularly desirable that additional data should be collected during at least a part of a second year in order that it could be seen to what extent those of the first year might have a somewhat general application, and in order also that by a combination of the two sets of data a broader basis might be had for generalizations of more stable value; and this was done by a substantial repetition, during the three summer months of 1909, of the summer program of 1907. There was a further special reason for repeating our first mid­ summer observations. The length of the State of Illinois from north to south brings its extremes into materially different climates, and neces­ sitates its division, for comparative purposes, into northern, central, and southern sections; but these differ also in the time of onset of the annual seasons and the length of the period over which each season • The Midsummer Bird Life of Illinois. By Stephen A . Forbe s. Bul. Ill. State Lab. Nat. Hist., Vol. IX, p . 373-404. t An Ornithological Cross-section or Illinois In Autumn. By Ste phen A. Forbes. Bul. Ill. State Lab. Nat. Hist., Vol. VII, p. 332-333. 188 prevails.t The observations of the summer of 1907 were made in the early part of the season (June 4 to July 1) for southern Illinois, at the middle of it (July 9 to 24) for central Illinois, and during the latter part of it (July 29 to August 3) for the northern part of the state. By this program observations of the early summer in southern Illinois were brought into comparison with those of late summer in the northern section, and it was hence not possible to distinguish clearly in all cases between regional and seasonal differences in the bird life of these sections. To minimize differences due to season merely, in order that those due to climate and other sectional factors might stand out more clearly, the field program of the second summer (that of 1909) was so arranged that observations were made in early, middle, and late summer in each section of the state, those for southern Illinois June 8 to 17, July 13 to 21, and August 17 to 26; those for central Illinois June 22 to 29, July 23 to 31, and August 28 to September 4; and those for northern Illinois June 30 to July 8, August 4 to 13, and September 6 to 15. Furthermore, in order to give greater variety and validity to the whole body of observa­ tions of the two years taken together, those of the second year were given different location and range from those of the first. In 1907 continuous trips had been made between widely separated points, but in 1909 certain places were chosen as centers of characteristic districts, and from these relatively short trips were made in various directions. In this second summer the total distance traveled by the observers was 654 miles, and the area covered by their observations was 11,624 acres-an increase of 51 per cent. over that of the earlier year. Forty­ one per cent. of the total area of 1909 was in northern, 33 per cent, in central, and 26 per cent. in southern Illinois. The area covered in the two summers was 19,317.6 acres. Notwithstanding the effort made to give a different range to the later observations, the general features of the country traversed in the two years were very similar, as is shown by the following table of the CROP AREAS, PER CENT., SUMMERS OF 1907 AND 1909 Northern Illinois Central Illinois Southern Illinois Crops 1907 1909 1907 1909 1907 1909 Corn 31 31 46 43 23 28 Small grain• 27 24 26 28 21 36 Forage crops 37 38 27 25 44 33 Miscellaneous 5 7 1 4 12 14 * Including stubble and plowed ground. t The significance of the north and south extension of the state is further illus­ trated by the fact that three faunal zones are r epresented In its area, the lower austral in southern Illinois, the upper austral in central, and the transitional in the extreme northern part ot the state. 189 percentage of the whole area of observation for each year which was in each of the principal farm crops. For the northern and central parts of the state the agreement between the two years is remarkably close, but there are noticeable differences between them in southern Illinois, due to the larger area in small grain in 1909, an increase evidently made at the expense of the forage crops. The comparison just made assures us, however, that any differences of importance noted in the bird life of the two years in the different sections were not attributable to differences in agricultural conditions. The most striking general difference was in the seeming greater abundance of birds in 1909, in all three sections of the state. It is best shown in the following table of the numbers of birds recognized and counted and the number per square mile in each section of the state and in the state as a whole. Section Southern Central Northern State NUMBERS OF BIRDS SEEN AND NUMBERS PER SQUARE MILE, SUMMERS OF 1907 AND 1909 Number of birds Numbers per square mile 1907 I 1909 I Both years 1907 I 1909 I Both years 2667 3973 6640 682 841 769 2047 6368 8415 650 1071 925 3026 7647 10673 610 1021 857 7740 17988 25728 644 990 852 From this it appears that the number seen per square mile averaged 54 per cent. larger for ~he whole state in 1909 than in 1907, and that the increase was especially striking in central Illinois, where it amounted to 65 per cent. That this was a general and not a local phenomenon in Illinois is shown by our tables of the number of birds per square mile of different crops in different sections of the state. From these it appears that the numbers per mile recorded in 1909 exceeded those of 1907 in fields of corn, oats, stubble, plowed ground, pasture, orchards, woodlands, and yards and gardens and fell short of the 1907 numbers in wheat, meadow, shrubbery, and waste and fallow, and that the total of the areas of the first of these lists was 14,872 acres and that of the second list 4333 acres, the birds being more abundant in 1909 than in 1907 on tracts aggregating nearly three and a half times as great an area as those in which the 1909 numbers were smaller than those of 1907. The possible causes of so sudden and so great an apparent increase in the bird population of the state are too numerous and too wide-spread to come within the range of our inquiries; but the fact itself is important, especially as showing the need of prolonged investigation as a basis for 190 generalization in this field. Among the minor illustrations of this fact is the disagreement of the second year's data with a conclusion reached in an earlier paper* already cited, to the effect that the total number of our summer birds increases from north to south in Illinois. This seemed to be true by our data of 1!)07, but it was not at all so by those of 1909; and when the averages for both years are brought together, as in the preceding table, we see that the numbers per square mile are larger for southern Illinois than for northern but are largest of all for the central part of the state. NUMBERS OF GREGARIOUS AND SOLITARY SPECIES, RESPECTIVELY In a search for possible causes of the marked increase of numbers throughout the state noted in 1909, we have tabulated separately the data for our nine principal gregarious species, namely, the English sparrow, quail, mourning dove, crow, bobolink, cowbird, red-winged blackbird, crow-blackbird, and goldfinch, and have brought these into comparison with the data for the solitary species remaining, with the result that the increase in numbers in 1909 is found almost wholly in the gregarious group. While the numbers of the solitary species per square mile in 1909 average for the whole summer and the whole state 6 per cent. larger than in 1907, those for the gregarious species are 2.39 times as large. This fact raises the question whether the indicated increase in num­ bers was real, or only apparent and due to the insufficiency of our data. The unit of observation of the solitary species is the single bird, while that of the gregarious species is often a group of companions varying from a small flock to many hundreds. A record of a thousand solitary birds thus represents a larger number of separate observations than one of the same number of gregarious birds, and the averages in the latter case are less likely to be valid than in the former_. The social birds are not always gregarious, however, most of them scattering during their nesting season and often when in search of food, assembling only at the time of the spring migration and in late summer and fall after their young have become independent. That the actual number of gregarious birds to a single observation is much smaller than might be supposed, is shown by one of our tables which enables us to make a comparison between seven gregarious species and seventeen of the most abundant solitary species with respect to the average numbers recorded for each field or other unit of area covered by the summer survey of 1907. By this table it appears that the gregarious birds ranged in number per record from 2.4 for the mourning dove to 9.1 for the crow-blackbird, with an average of 6 per record for the seven species; while the corresponding numbers for the seventeen solitary species ranged from 1.3 for the brown thrasher and the red-headed woodpecker • The Mids umme r Bird Life of Illinois, loc. cit., p , 375-376. 191 to 3.5 for the robin, with a general average of 2.1 per record for the group. In other words, the number of gregarious birds to the observa­ tion was less than three times the number of the more abundant solitary species; but it follows from even this fact that for equally valid averages and generalizations the number of observations of gregarious birds should be about three times as great as for the solitary species. A further examination of the details of our tabulated data concern­ ing the most abundant gregarious birds leads us to believe that, with three exceptions, the variations in numbers at different times and in the several sections of the state are not unusual as compared with the range of corresponding variations in the numbers of the solitary species, and ACREAGE OF SURVEY AND NUMBERS OF MO~T ABUNDANT GREGARIOUS BIRDS, SUMMERS OF 1907 AND 1909 Acreage of Survey: Southern Illinois Central Illinois Northern Illinois 1907 2504.08 2017.09 3172.39 I· 1909 3023.11 3806.80 4794.14 I Both years 5527.19 5823.88 7966.53 Totals I 7693.56 \ 11624.05 I 19317.60 Numbers of gregarious birds recorded: English sparrow Quail Mourning dove Crow Bobolink Cowbird Red-winged blackbird Bronzed grackle (crow-blackbird) Goldfinch Totals Birds per square mile Numbers of above birds with three doubtful species omitted Birds per square mile 1414 91 461 89 119 102 347 900 158 I 3681 I 306 2560 I 213 4239 224 670 287 631 1845 573 2455 231 111155 I 614 6224 I 343 5653 315 1131 376 750 1947 920 3355 389 I 14836 I 492 8784 291 192 that with these exceptional cases eliminated our recorded numbers of gregarious birds per square mile may be accepted as fairly representa­ tive of the actual facts for these two years. The doubtful species are the cowbird, the crow-blackbird, and the bobolink, to be dropped from the computation for the following reasons: The crow-blackbirds recorded, numbered 900 in 1907 and 2455 in 1909, and we omit the species from this comparison because the excess was found mainly in September in two situations in a single section of the state-that is, in yards and in corn fields in northern Illinois. The cowbird is omitted for a like reason, its numbers being 93 in 1907 and 1845 in 1909, of which 1302 were in large flocks seen in September in yards and corn fields, in northern Illinois. The bobolink is dropped merely because of the restriction of its summer range to the northern part of the state, where the numbers seen were 743 for the two years together as compared with seven ( doubt­ less caught in migration) in the two other sections of the state. vVith these three species omitted, we have remaining 235 gregarious birds to the square mile in 1907 and 343 to the mile in 1909, an increase in the latter year of 46 per cent., which we are disposed to take as actual , but of the causes of which we can offer at present no explanation. MosT ABUNDANT SPECIES, BOTH YEARS The list of birds recognized and counted in the summer months of 1907 contained 85 species names and the corresponding list for 1909 contained 117 names. Most of the species were seen in both years, the entire list for both numbering only 125 ; or if we include the species noted in an orchard survey of 1908, the total is 133. Many of the species of these lists were represented by relatively insignificant numbers, 21 of the species seen in 1907 and 19 of those seen in 1909 making up , 5 per cent. of the total number of birds seen in those years. The 21 most abundant species of 1907 aggregated 550 to the square mile, and the remaining 68 species only 95 to the mile; and the 19 most abundant species of 1909 aggregated 842 to the mile, and the remaining 88 species only 148. The 19 most abundant birds of 1909, making up 85 per cent. of all the birds seen in that year, are all on the corresponding list for 1907, the latter differing only by the addition of two names, grasshopper sparrow and upland plover, not on the 1907 list. When we com­ pare the numbers, and especially the ratios, of the different species ( the base of the percentages being the total numbers of birds seen), we find a fairly good agreement for the two years, with a few somewhat striking differences, largely of the more gregarious species, as shown by the following table. The most marked discrepancies between the two years are in the percentages of the cowbird, bobolink, and dickcissel, those of the cow­ bird in one year being about nine times those in the other, and those of I I i I ' ,' l I 193 THE MOST .ABUNDANT BIRDS, SUMMERS OF 1907 AND 1909 Species English sparrow Meadowlark Bronzed grackle* Mourning dove Dickcissel Red-winged black- bird Prairie horned lark Flicker Robin Field sparrow Goldfinch Kingbird Bobolink Grasshopper spar- row Brown thrasher Red-headed wood- pecker Barn swallow Cowbird Quail Upland plover Crow Totals Per square mile Number seen 1907 1414 1025 900 461 393 347 296 197 194 186 158 126 119 110 104 99 96 102 91 89 89 1909 4239 1434 2455 670 353 573 414 419 417 294 231 184 631 0 204 259 159 1845 224 0 287 1907 and 1909 6653 2459 3355 1131 746 920 710 616 611 480 389 310 750 110 308 358 255 1947 315 89 376 Per cent. of all birds seen 1907 1907 1909 and 1909 18.2 13.2 11.6 6.0 5.1 4.5 3.8 2.5 2.5 2.4 2.0 1.6 1.5 1.4 1.3 1.3 1.2 1.3 1.2 1.1 1.1 23.6 8.0 13.6 3.8 2.0 3.2 2.3 2.3 2.3 1.7 1.3 1.1 3.6 0.0 1.1 1.4 0.9 10.3 1.2 0.0 1.6 22.1 9.6 13.0 4.4 2.9 3.6 2.8 2.4 2.4 1.9 1.5 1.2 2.9 0.4 1.2 1.4 1.0 7.6 1.2 0.3 1.5 16596 115,292 , 21,888 85.3 85.0 1 85.1 I I 549 I 842 I 725 I I Ranking as to numbers 1907 1909 1 2 3 4 5 6 7 8 9 JO 11 12 13 14 15 16 17 18 19 20 21 1 4 2 5 11 7 9 8 10 12 15 18 6 17 14 10 3 16 13 1907 and 1909 1 3 2 6 8 6 9 10 11 12 13 17 7 20 18 I 15 19 4 16 21 14 the other two species two and a half times. By combining the numbers of each species for both years, we get the most authentic record obtain­ able from our data, and by this means we see that the eleven principal species of the summer birds of the whole state, were the English sparrow, crow-blackbird, meadowlark, cowbird, mourning dove, red-winged black­ bird, bobolink, diskcissel, prairie horned lark, flicker, and robin, abundant in the order named. These eleven species taken together aggregated 74 per cent. of all the birds counted in the summer months of the two • Commonly k nown in Illinois a s the crow-blackbird. or common blackbird. 194 years and averaged as a group 624 to the square mile, while the num­ bers of the 114 remaining species amounted to 228 to the mile. THE MOST ABUNDANT BIRDS BY SECTIONS OF THE STATE Eighty-five species and one variety of birds were recognized and counted in southern Illinois in the summers of 1907 and 1909 and twenty-two of these were so abundant as to comprise 83 per cent. of the total number of birds, leaving but 17 per cent. for the other sixty­ four species. Otherwise stated, twenty-two species averaged 250 birds each while the remaining 64 species averaged only eighteen each. The more common 25 per cent. of the different kinds of birds were about fourteen times as numerous per species as the less common 75 per cent. The commoner group of 22 species averaged 638 birds to the square mile, and the less common group 130 to the mile, the former with one bird to the acre and the latter with about five acres to the bird. N U M BERS OF PRINCIPAL S UMMER BIRDS OF SOUTHERN ILLIN OIS IN 1907 AND 1909 ( 22 SPECIES) ( 83 PER CENT. OF ALL THE BIRDS SEEN) Meadowlark . . ..... ........ ..... .. .. .. 1293 English sparrow . . . . . . . . . . . . . . . . . . . . . 795 Mourning dove ..... .. . .. .. .. . .. . . . ... 518 Field sparrow . . . . . . . . . . . . . . . . . . . . . . . . 322 Dickcissel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 Red-winged blackbird. . . . . . . . . . . . . . . . . 278 Bronzed grackle . . ....... . ... .. .... . . . 274 Quail . ........ ... . .. . . . ... . ... . ... . . . 241 Robin . .. ... . .... . .. .. . . .... .. . . .. .. . . 165 Brown thrasher . . . . . . . . . . . . . . . . . . . . . . 137 Kingbird . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Cowbird . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Mockingbird . . . . . . . . . . . . . . . . . . . . . . . . . 112 Blue jay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 R ed-headed woodpecker . . . . . . . . . . . . . . . 105 Orchard oriole . . . . . . . . . . . . . . . . . . . . . . . 103 Bluebird ..... . . . .- . . . . . . . . . . . . . . . . . . . . 96 Grasshopper sparrow . . . . . . . . . . . . . . . . . 93 Killdeer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Flicker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Maryland yellow-throat . . . . . . . . . . . . . . . 78 Indigo bunting . . . . . . . . . . . . . . . . . . . . . . . 75 Total . .. .... .. . . .. . . . . . . . . ... . .. . 5514 W hen we come, however, to compare southern with central Illinois, we find a striking difference in respect to the number of dominant species. The southern part of the state is much more broken and diversi­ fied than the central-contains, that is, a great er variety of situations, each with its more or less definite group of characteristic or dominant 195 birds. The number of these dominant species is thus much larger and the number of birds to the species is correspondingly smaller than in the comparatively level, uniform territory of central Illinois. Although the areas covered by the bird survey were approximately equal in these two sections of the state,* and the number of birds seen was nearly 27 per cent. greater in central Illinois than in southern, the number of species was 20 per cent. smaller and the dominant species were much fewer-85 per cent. of all the birds belonging to thirteen species instead of twenty-two, and these averaging 553 to the species instead of the 250 of southern Illinois. The average frequency of all birds in the central section was 925 per square mile, and 791 of these ( 86 per cent.) belonged to the thirteen more abundant species; while the birds of the remaining fifty-nine species, if equally distributed, would each have had about ten acres to itself. NUMBERS OF PRINCIPAL BIRDS OF CENTRAL ILLINOIS, SUMMERS OF 1907 AND 1909 ( 13 SPECIES) (85.5 PER CENT. OF ALL THE BIRDS SEEN) English sparrow . ..... . ..... .... ... ... 1865 Cowbird ............................. 1744 Bronzed grackle ...................... 1111 Meadowlark . . . . . . . . . . . . . . . . . . . . . . . . . . 630 Mourning dove . . . . . . . . . . . . . . . . . . . . . . . 407 Dickcissel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Red-winged blackbird . . . . . . . . . . . . . . . . 225 Prairie horned lark . . . . . . . . . . . . . . . . . . 204 Flicker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 Robin ................ ........ ....... 170 Brown thrasher . . . . . . . . . . . . . . . . . . . . . . 133 Red-headed woodpecker ............... 125 Crow ................................ 115 Total ............................ 7196 Northern Illinois has a somewhat more uneven and diversified sur­ face than the central section of the state, but much less so than the southern, and consistently with these facts we find that 15 of its species made up 84.4 per cent. of its bird population in J 907 and 1909, 79 species contributing but 15.16 per cent., the former group averaging 698 birds of each species and 723 to the square mile, and the latter group but 21 to the species and 131 to the square mile. Illustration from M ay-beetles.-The relation shown in the com­ plexity of an environment and the number of dominant species of birds, which it contains is paralleled in a convincing way by data derived from extensive collections of Illinois May-beetles made for the senior • 5527.19 acres in southern IJl!nois and 5823.88 In central. 196 NUMBERS OF PRINCIPAL BIRDS OF NORTHERN ILLINOIS, SUMMERS OF 1907 AND 1909 ( 15 SPECIES) (84.4 PER CENT. OF ALL THE BIRDS SEEN) English sparrow ...................... 2993 Bronzed grackle ...................... 1970 Bobolink ... . .. .. .. .......... ... ...... 743 Meadowlark . . . . . . . . . . . . . . . . . . . . . . . . . . 536 Prairie horned lark . . . . . . . . . . . . . . . . . . 451 Red-winged blackbird . . . . . . . . . . . . . . . . . 417 Flicker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350 Robin ... . ..... ... ....... . ........ .... 276 American goldfinch . . . . . . . . . . . . . . . . . . . 257 Mourning dove .. .. .. . ................ 206 Crow . ....... ..... ... . . .. .... .. .. .... 197 Barn swallow . . . . . . . . . . . . . . . . . . . . . . . . 160 Vesper sparrow ...................... 151 Grasshopper sparrow . . . . . . . . . . . . . . . . . 151 Dickcissel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Total ............................ 9007 author in 1907 to 1912 when he was state entomologist of Illinois. In an article on the subject published in the Twenty-ninth Report of that office* is a tabulation of the distribution by sections of the state of 114,493 specimens of thirty-four species of May-beetles (Phyllophaga), from which it appears that, with these insects also, the number of domi­ nant species is greatest in southern Illinois, where 8 out of 30 species make up 85 per cent. of the total number taken; smallest in central Illinois, where 3 of 28 species made up 81.7 per cent., and 4 species made 91 per cent.; and intermediate to these in the northern part of the state, where 5 of 21 species made up 85 per cent. of the whole number taken. The average number of each dominant species differs, of course, in the same direction. In southern Illinois the eight most abundant May-beetles were represented by an average number of 2959 specimens each and the remaining 22 by only 103 each. In central Illi­ nois the corresponding numbers were 17,952 each for the four common­ est species and 291 each for the 24 others, and in northern Illinois they were 2619 each for five of the species and 112 each for the remaining 21. THE MOST ABUNDANT SPECIES OF THE WHOLE STATE By uniting into one the three preceding lists and filling in the numbers of each species in all the columns for the sections of the state, we make up the following table, in which it is easy to distinguish the eleven principal species for the whole state. This comprises all whose numbers are larger than 500, and the twenty-nine species of this table • A General Survey of the May-beetles (Phyllophaga) of Illinois, by S. A. Forbes, State Entomologist, p. 23-70. 197 aggregate more than 90 per cent. of all the birds recorded during the two summers covered by this discussion. NUMBERS OF PRINCIPAL BIRDS IDENTIFIED IN EACH SECTION, AND IN THE WHOLE STATE* ( 29 SPECIES) A.O.U. Species s. C. N. Whole numbers Ill. Ill. Ill. state 273 Killdeer 87 23 64 174 289 Quail 241 53 21 315 316 Mourning dove 518 407 206. 1131 406 Red-headed woodpecker 105 125 128 358 412 Flicker 82 184 350 616 444 Kingbird 119 52 139 310 474b Prairie horned lark 55 204 451 710 477 Blue jay 111 37 52 200 488 Crow 64 115 197 376 494 Bobolink 5 2 I 743 750 495 Cowbird 116 1744 87 1947 498 Red-winged blackbird 278 225 417 920 501 Meadowlark 1293 630 536 2459 506 Orchard oriole 103 3 6 112 511b Bronzed grackle 274 1111 1970 3355 English sparrow 795 1865 2993 5653 529 Goldfinch 74 58 257 389 540 Vesper sparrow 1 22 151 174 546 Grasshopper sparrow 54 93 151 298 552 Lark sparrow 93 6 7 106 563 Field sparrow 322 59 49 430 598 Indigo bunting 75 14 27 116 604 Dickcissel 314 283 149 746 613 Barn swallow 4 91 160 255 681 Maryland yellow-throat 78 19 7 104 703 Mockingbird 112 7 1 120 705 Brown thrasher 137 133 38 308 761 Robin 165 170 276 611 766 Bluebird 96 22 79 197 \ Numbers of dominant species 22 13 16 11 • Black-face figures show dominant species in each section. CHANGE OF NUMBERS FROM NORTH TO SOUTH In an earlier paper on the midsummer bird-life of Illinois, already cited, it was reported that, according to our data of 1907, the English sparrow decreased in numbers in the summer time from north to south in Illinois, but that the numbers of the native summer residents increased in that direction by something like 16 per cent. for central Illinois and 198 29 per cent. for southern Illinois. When, however, we bring together our data for the two seasons, as in the table on page 197, and compare sectional numbers for the different species, we find that ten species sufficiently abundant to make them available for comparison show a marked progressive increase in numbers from north to south, and that eleven species show a decrease in that direction as follows: THE MORE ABUNDANT Bmns WHICH SHOW A PROGRESSIVE CHANGE IN NUMBERS IN SUMMER FROM NORTH TO SOUTH IN ILLINOIS (DATA OF 1907 AND 1909) Increase Quail Mourning dove Meadowlark Orchard oriole Lark sparrow Field sparrow Dickcissel Maryland yellow-throat Mockingbird Brown thrasher Decrease English sparrow Red-headed woodpecker Flicker Prairie horned lark Crow Bobolink Bronzed grackle Vesper sparrow Grasshopper sparrow Barn swallow Robin The general summer range of two of the above species-the mocking­ bird and the bobolink-is so definitely limited as to make their pre­ ponderance in southern and northern Illinois respectively a matter of course. Indeed, it seems probable that in so level and uniform a state as Illinois, where there are few topographical barriers to the distribu­ tion of birds, the contrasts in numbers between the north and the south are mainly due to differences in the general range of the species, those whose centers of general distribution lie to the northward of the state diminishing in number in Illinois toward the southern boundary of their midsummer range, and the Illinois numbers of those whose dis­ tribution centers lie southward increasing in that direction. The degree of overlapping and intermingling of northern and southern species in central Illinois will vary somewhat with the character of the season, as the different species differ in susceptibility to peculiari­ ties of temperature, humidity, and other features of the spring and summer weather. Variations in the abundance or scarcity of the prin­ cipal elements of the food of the various species may have a similar effect to limit or extend their midsummer distribution in a way to affect them variously. Those, for example, with a fixed and narrow range of food preferences will be severely checked in their migrations by a local deficiency ot their favorite food, while others, with less discriminating tastes , may find the deficiency of certain food elements compensated by an unusual abundance of other food. i , .. 199 BIRDS AND VEGETATION AREAS The several vegetation areas of our survey, may be arranged for convenient comparison in the order of the numbers of birds to the square mile, as in the following table. VEGETATION A.BEAS AND BIRDS PER SQUABE MILE IN EACH, THE WHOLE STATE,* SUMMERS OF 1907 AND 1909 Vegetation Orchards Yards and gardens Swamps Woodlands Pastures Shrubbery Meadows Wheat, rye, and barley Waste and fallow Plowed ground Stubble Corn Oats Miscellaneous I Acres \ Birds 117.69 557.39 83.66 111.96 5196.06 93.31 2763.02 822.36 654.17 300.16 1069.46 6433.63 2485.57 29.16 3943 3418 1974 1846 1068 1056 910 827 787 670 669 593 514 329 * The general state average of all birds, both summers, taken together, was 852 to the square mile. Half of these 14 classes of area carry a bird population exceeding the average for the state as a whole, and half of them fall below that average. Of the larger areas, each comprising from 1000 to 6000 acres or more and aggregating 85 per cent. of all our census territory, pas­ tures and meadows stand highest, with corn and oats falling much below the average. Generally speaking, the smaller areas attract the largest numbers of birds to the square mile, possibly because, as we have found to be clearly the case with orchards,* the characteristic birds of a single kind of vegetation area are scattered where the area is large, and concentrated where it is small. Of these smaller areas, orchards stand much the highest, with nearly five times the average concentration, and yards and gardens next, the birds of all these situa­ tions showing by their local numbers, a high degree of adaptation to the companionship and life of man. Swamps and open woodlands are almost the only approximately wild places on our list, and these contain about twice as many birds as the general average, but less than half • "The Orchard Birds o! an Illinois Summer", by Stephen A. Forbes and Al!red 0. Cross. Bul. Ill. State Nat. Hist. Survey, Vol. XIV, p. 1-8. 200 as many as the areas of human neighborhood. Their total of some 200 acres is, however, rather small for any definite inference. THE BIRD LIFE OF ILLINOIS p ASTURES On the 3796 acres of pasture whose bird population was accurately ascertained in the two summers, an average of 1068 birds to the square mile was found-1041 in northern, 1274 in central, and 937 in southern Illinois. If we separate the data for the different years, we find an average for the state of 881 to the square mile in 1907 and 1194 to the mile in 1909, the excess for the latter year being 36 per cent. in northern Illinois, 29 per cent. in central Illinois, and 30 per cent, in southern. The 6335 birds identified in pastures belonged to ninety-six species, but 85 per cent. of these belonged to twenty-three species, leaving but 15 per cent. for the other seventy-three. There was thus no small dis­ tinctive group of pasture birds, such as were found in some other habi­ tats, but the pasture was merely one of the preferred resorts of a rather long list of species, every one of which was, in fact, found in one or more other situations more frequently than there. The English sparrow stood at the head of the list of pasture visitants, but the meadowlark led the native birds in each year and in each section of the state, and was found in southern Illinois pastures more than twice as common as the sparrow. The crow-blackbird, or bronzed grackle, was third in order of numbers in both years and in the whole state, but it was surpassed in the southern part of the state by the field sparrow and the mourning dove. and in central Illinois by the cowbird. Among other more prominent birds were the flicker ( which was, how­ ever, only about a third as common in southern Illinois pastures as farther north), the robin, also much the least abundant in southern pastures, the prairie horned lark, much the commonest in northern Illi­ nois, and the red-winged blackbird. Comparing the data of the two years, we find 13 of the 23 most abundant species represented by notably larger numbers per square mile in 1909 than in 1907, two of them by fewer, and 8 by virtually equal numbers. The group of pasture birds thus gives the same indication of increased numbers in 1909 as do the combined data from all situa­ tions. Additional particulars concerning these species may be gathered from the following table. From the known food habits of the more abundant pasture species it appears that the meadowlark and the crow-blackbird are the kinds most serviceable, under ordinary conditions, as a pasture police for the control of injurious insects. When a considerable outbreak of a destruc­ tive species occurs, many other birds attracted by unusual chances for "loot" will come to the aid of the regular force; but it is to the less conspicuous services of constant residents and frequent visitants that the farmer must look for a steady pressure upon the multiplication 201 PRINCIPAL PASTURE BIRDS PER SQUARE MILE, SUMMERS OF 1907 AND 1909 Species I Southern Central Northern 1907 Meadowlark 240 168 79 143 Bronzed grackle 46 101 72 49 Cowbird 16 162 22 11 Robin 27 72 63 35 Prairie horned lark 21 27 72 47 Flicker 19 53 63 29 Mourning dove 50 76 14 31 Red-winged blackbird 34 27 35 23 Field sparrow 57 27 8 41 Red-headed wood- pecker 18 36 27 22 Bobolink 2 1 53 8 English sparrow 102 244 191 176 Goldfinch 8 9 37 17 Barn swallow 2 45 25 17 Brown thrasher 23 26 15 14 Kingbird 21 21 17 20 Crow 8 19 27 14 Bluebird 17 11 25 14 Quail 28 11 8 14 Killdeer 6 8 19 15 Dickcissel 18 21 4 13 Blue jay 15 9 10 11 Grasshopper sparrow 9 12 10 9 I Totals 787 1186 886 773 Per cents. of all birds 84 93 86 88 Whole 1909 state, both years 157 151 88 72 85 55 60 50 48 48 59 47 47 41 39 33 19 28 29 26 35 24 178 177 24 21 27 23 24 20 19 19 19 19 23 19 15 15 10 12 12 12 11 11 10 9 1038 932 87 87 of cutworms, grasshoppers, May-beetles, and other ordinary insect pests of the pasture. THE MEADOW BIRDS In Illinois meadows the meadowlark justified its name by an abundance virtually double that of any of the other "most abundant" birds-194 to the square mile as compared with 100 for the dickcissel and 94 for the English sparrow. In northern Illinois it was surpassed by the bobo­ link ( 201 to the square mile and 102 for the meadowlark), but the absence of the bobolink from the more southern sections reduced its meadow average for the state to 96. Fourteen species made up 82 per cent. of all the birds identified in meadows, and more than half the whole number of birds belonged 202 to the four species mentioned above. Next in order came the crow­ blackbird, red-winged blackbird, and grasshopper sparrow, found m nearly equal numbers per square mile, those for the seven other more abundant species ranging from 31 to the mile down to 9. PRINCIPAL MEADOW BIRDS PER SQUARE MILE, WHOLE STATE, Species Uplancl plover Mourning dove Flicker Kingbird Prairie horned lark Bobolink Red-winged blackbird Meadowlark Bronzed grackle English sparrow Grasshopper sparrow Dickcissel Barn swallow Robin SUMMERS OF 1907 AND 1909 I Southern Central Northern 1907 4 36 7 10 1 0 80 319 18 54 19 155 0 7 67 35 51 7 5 0 32 204 85 85 64 179 10 13 22 22 40 21 41 201 18 102 55 126 48 29 16 17 19 31 37 19 23 12 50 204 81 112 56 122 12 17 1909 30 27 26 11 19 166 34: 185 21 79 29 81 7 10 Whole state, both years 25 29 31 15 21 96 41 194 49 94 41 100 0 13 Totals I 710 I 837 I 758 I 795 I 725 I 749 Per cents. of all birds I 78.7 I 83.9 I 87.1 I 86.8 I 81.6 I 83.4 Compared with pastures, meadows were distinguished by the some­ what greater prominence of the meadowlark (19± to 151), the exclu­ sive habitation of the bobolink ( 96 to O), the much greater prevalence of the dickcissel · (100 to 12) and the grasshopper sparrow (·H to 10), and the greater abundance of the red-winged blackbird ( 41 to 33). As against this list of distinctive meadow birds there is a much longer list of those to which the meadow was less attractive than the pasture. The principal of these are the English sparrow ( 9-1 to the square mile in meadow and 177 in pasture), the crow-blackbird ( 49 to 72), the robin ( 13 to 50), the prairie horned lark (21 to -:1:8), the flicker (13 to -:1:7), and the mourning dove ( 29 to 41). With the possible exception of- the last, these differences are fairly consistent with the knO\rn food and habits of the several species. This ob.vious preference of the species mentioned for pastures over meadows is reflected in the average for the whole state of the meadow and pasture birds respectively (meadows. 910, and pastures, 10 5, to the square mile). 203 BIRDS IN SMALL GRAIN AND IN STUBBLE Wheat and oats, judging by our data, offer very similar inducements ( or lack of special inducements) to birds, but with one notable exception, that of the mourning dove, of which ten times as many to the ·square mile were found in fields of wh~at as in oats ( 141 to 14, respectively). Differences seen in the numbers of the gregarious and erratic cow­ birds and grackles seem to have little significance, and may probably be attributed mainly to the mere chances of unequal distribution, but with these species eliminated, the numbers of birds in wheat exceed those in oats by about 34 per cent. NUMBERS PER SQUARE MILE OF PRINCIPAL BmDS IN SMALL GRAIN AND STUBBLE, WHOLE STATE, SUMMERS OF 1907 AND 1909 (Wheat, rye, and barley, 822 acres; oats, 2486; stubble, 1069.) Species /wheat*! Oats I Stubble Quail 14 4 9 Mourning dove 141 14 40 Prairie horned lark 24 5 11 Crow 21 12 11 Bobolink 4 16 23 Cowbird 121 11 1 Red-winged blackbird 26 21 1 Meadowlark 47 50 89 Bronzed grackle 156 92 4 English sparrow 147 163 159 Goldfinch 8 10 10 Dickcissel 27 28 1 Cliff swallow 2 3 12 Robin 3 4 8 All birds 827 514 669 • Includes rye and barley. Fields of small grain would seem to undergo so great a change as bird resorts as the grain is cut and shocked, that we might well have anticipated a marked contrast in the species and numbers found in them after harvest, but our table does not confirm this expectation, the differences between stubble fields and those of uncut grain being chiefly in the gregarious cowbirds and blackbirds, and otherwise not noticeably greater than those betweeo. fields of oats and wheat. As a further test of this conclusion, we have tabulated separately the numbers of all species found in fields of small grain, before harvest and after the grain had been cut and shocked, but we find few consistent 204 or significant differe_nces, vari.ations in numbers in the contrasted situa­ tions being generally erratic and in different directions at different times. A comparison of the columns of our table for the two years gives us, in fact, . an impression that the grain fields are resorted to by most birds for occasional and temporary reasons, such as the superabundance of easily accessible and especially desirable food in the shocked wheat, or a scarcity of the ordinary food of the species elsewhere. The marked preference of the mourning dove for harvested wheat over any other of the situations of our table, and the unusual abundance of meadow­ larks in 1909 in fields of harvested oats are probably to be thus accounted for; but the apparent preference of the dickcissel for standing grain is not so easily understood. Its uniform averages of 42 to the square mile in this situation, of only 6 or 7 in fields of shocked grain, and virtually none in naked stubble fields mean, on the face of the figures, that it finds in the growing grain important advantages which largely disappear when the grain is cut; but in view of the habits of the species, it seems to us more likely that the difference is due to the mere advance­ ment of the season. The nesting period of the dickcissel is practically over by the time the grain is all harvested, and by the first week in August most of the birds have assembled in secluded roosts for their postjuvenal and postnuptial molts, soon after which they leave for the South. In fact, less than 10 per cent. of our dickcissels were seen after July 31 in fields of grain, either cut or uncut, and their relative scarcity in shocked wheat or oats is very likely due to their gradual withdrawal from the open country. ACREAGE SURVEYED OF WHEAT AND OATS, UNCUT AND CUT, WHOLE STATE, MIDSUMMERS OF 1907 AND 1909 Crops Wheat Oats 1907 Uncut I Cut Acres 134.52 I 151.14 531.41 601.07 1909 Uncut I Cut Acres 201.15 1123.90 454.28 669.13 I 205 ALL BIBDB, PRINCIPAL SPECIES, AND NATIVE BIBDS IN WHEAT AND OATS, CUT AND UNCUT, MIDSUMMERS OF 1907 AND 1909 1907 Wheat Oats Uncut I Cut Uncut I Cut Birds English sparrow Mourning dove Meadowlark Prairie horned lark Dickcissel All birds Native birds English sparrow Mourning dove Meadowlark Prairie horned lark Dickcissel All birds Native birds Num- To Num- To Num- To Num- To bers sq. mt. bers sq. mt. bers sq. mi. bers sq. mt. 77 20 12 0 9 153 76 25 8 12 23• 10 1 133 108 371 95 57 0 43 728 362 80 25 38 74 32 I 423 I 344 9 57 12 8 3 291 282 15 29 0 0 1 128 I 113 38 55 241 13 51 32 34 0 13 49 1228 385 1194 330 1909 77 150 0 0 6 636 I 684 611 9 23 8 29 813 I 202 66 231 16 6 39 57 0 14 59 6 469 422 397 191 861 13 32 4 41 1146 285 417 16 76 1 6 1 842 I 425 245 6 61 15 6 445 203 379 15 72 1 6 805 426 • Twenty In one flock. THE BIRDS OF THE CORN FIELD With the exception of occasional raids made on fields of corn by flocks of crow-blackbirds and cowbirds in fall to feed on grain torn from the tips of the ears, there is little in our data to indicate that our Illinois birds find any special lure or attraction in corn fields. It is true that the English sparrow was found there in numbers averaging 130 to the square mile, but this was less by 57 than the average of the sparrow for the whole state. The blackbird, on the other hand, was more abundant in corn fields than its general average (138 and 111 to the 206 square mile respectively), as was also the cowbird ( 88 in corn fields and 64 in the state at large). None of the eleven remaining "more abundant" species necessary to bring the total up to 82.5 per cent. of all the corn field birds, was present in greater number than 29 to the square mile, the ratio of the mourning dove. The heterogeneous composition of this list of fourteen species and the moderate average numbers of each in corn fields . suggests, indeed, that their presence there was "accidental" rather than purposive, and we find no evidence ir:i our records, with the two exceptions mentioned, that there is any group of corn field birds, properly so-called. In other words, we can not say that the corn plant either profits or suffers from the visits of birds to the fields in which it is growing ( again excepting, of course, the cowbird and the crow-blackbird) to any extent which we have been able to discover. PRINCIPAL Bmos PER SQUABE MILE OF CORN, SUMMERS OF 1907 AND 1909 . Species Southern Central Northern 1907 Quail 24 4 5 2 Mourning d'ove 50 32 14 26 Red-headed woodpecker 10 6 3 4 Flicker 5 9 14 . 7 Prairie horned lark 6 29 16 20 Crow 3 9 14 4 Cowbird 15 213 2 6 Red-winged blackbird 14 7 30 9 Meadowlark 25 7 2 10 Bronzed grackle 32 133 206 60 English sparrow 49 120 189 50 Goldfinch 4 5 19 12 Vesper sparrow 1 3 18 6 Brown thrasher ' 9 9 2 7 Brnos ON PLOWED GROUND 1909 Both years 9 6 32 29 7 6 12 10 19 19 13 10 141 88 23 18 9 9 188 138 181 130 9 10 10 8 6 6 Ground plowed for planting but not yet planted can scarcely be said to resemble any natural habitat, or be expected to serve as a place of assemblage for any definite group of birds, and our data, derived from three hundred acres of plowed fields, chiefly in southern Illinois, are in accord with this supposition. A record of 314 birds occurring on this area, equivalent to the very respectable average of 670 to the square mile, is attributable mainly to the prairie horned lark, which has an unex­ plained but well-known preference for bare earth as a resting place. On plowed ground it was usually feeding busily on tiny weed seeds lodged in the soil, as shown by its actions and by the contents of crops examined. It was more than twice as abundant in plowed fields (162 to the square 207 mile) as any other species, the next in order being the mourning dove (77) and cowbird (49). These and four other species-the killdeer (58), robin and upland plover ( 34 each), and English sparrow ( 30 )-together made up 86 per cent. of all the birds recognized on plowed ground. The occurrence here o.f two species of shore birds in some numbers (22 examples of the killdeer and 14 of the upland plover) was probably due to their search for earthworms and insect larvae in the so£ t earth. THE BIRDS OF THE SWAMPS Open swampy lands are so scarce in Illinois that in 1070 miles of travel made in the summers of 1907 and 1909, only 4.6 miles were over swamps. In the area of 83.66 acres thus covered, 258 birds, belonging to thirty species, were identified, an average of 1974 birds to the square mile--about two and a quarter times the general average for the whole state. Two thirds of the swamp area was in northern Illinois, and there more than three fourths of the swamp birds were found. All of our thirty speciees were represented in this northern list, while on the nine­ teen acres of southern Illinois swamp there were but five species (the red-winged blackbird, crow-blackbird, meadowlark, dickcissel, and Mary­ land yellow-throat); and in 2¾ acres in central Illinois there was but one--the red-winged blackbird. The six species of the following table made up 82.6 per cent. of all the birds identified in swamps. PRINCIPAL Bums OF ILLINOIS SWAMPS, SUMMERS OF 1907 AN--0 1909 NUMBERS PER SQUARE MILE Red-winged blackbird 1125 Bronzed grackle 207 Bobolink 130 Quail 76 Green heron 46 Long-billed marsh wren 46 BIRDS OF THE OPEN w OODS Our data concerning the woodland birds are rather meager, mainly because it was impossible to use our method of identification and enumer­ ation in any except open woodlands of comparatively small trees, and the one hundred and twelve acres accurately covered consequently made too small and too special an area to be fully representative. Furthermore, the southern Illinois forest area surveyed was more than twice as large as that of all the rest of the state, and hence the forest birds of the southern section predominate strongly in our lists for the state as a whole. About half of the fifty species recorded from woods were distinc­ tively forest birds, rarely if ever seen in the open fields, and especially adapted by habit, preference, and sometimes by structural endowment 208 also, to life among trees. Nothing of the sort can be said of the birds of the pasture or the stubble field or of other distinguishable vegetation areas of the open country. The forest is a more complex environment than the meadow or the grain field, and its bird society is less dominated by a few con­ spicuous species. Thirty-one of the fifty species of our list were, in fact, necessary to bring our total of the more abundant kinds up to 85 per cent. of the whole number of birds; and the most abundant of these, the blue jay and the field sparrow, averaged only 194 and 131 to the square mile respectively. These were followed by the flicker, with 97 to the square mile, the robin, with 86, the brown thrasher and crested flycatcher, 69 each, and these, in order of numbers, by the wood pewee, crow, and mourning dove, with other species in ratios gradually decreasing to 17 to the square mile. The aggressive and presuming English sparrow, usually at the top of our lists, was in PRINCIPAL WOODLAND BIRDS (85 PER CENT, LIST) IN ORDER OF NUMBERS PER SQUARE MILE, WHOLE STATE, SUMMERS OF 1907 AND 1909 Blue jay Field sparrow Flicker Robin Crested flycatcher Brown thrasher Wood pewee Crow Mourning dove Red-headed woodpecker Towhee Indigo bunting Tufted titmouse Bronzed grackle English sparrow Cardinal Bluebird Redstart Goldfinch Quail Downy woodpecker Cowbird Red-winged blackbird Maryland yellow-throat Bewick's wren Dickcissel Black and white warbler Wood thrush Turkey vulture Sparrow hawk Yellow-bellied flycatcher 194 131 97 80 68 69 63 63 61 51 61 51 51 46 46 46 46 46 40 34 34 34 34 34 34 23 23 23 17 17 17 209 the fourteenth place of this series, with an average of only 46 to the mile, and no more abundant than the bluebird or the cardinal. The yearly ratios of these woodland birds (2187 to the mile in 1909 and 1441 in 1907) confirm· our general conclusion that birds were much the more numerous in Illinois in 1909. BIRDS IN ORCHARDS We have already reported on the orchard birds of a southern Illi­ nois summer, with some reference to other parts of the state, in a paper* in which we made special use of data obtained in August and September of 1908 by a trip through a commercial orchard district of that section; and we have here to report more fully on the product of a survey of 117.69 acr~s of farm orchards only, of which 71 per cent. was in southern, 18 per cent. in central, and 11 per cent. in northern Illinois. In these orchard belts, 825 birds were identified, equivalent to 4026 to the square mile. The English sparrow, however, made up more than half this number, leaving 1987 native birds to the square mile. Next to the sparrow, the more abundant species were the mourning dove (256 to the mile), quail (212), field sparrow (190), crow-blackbird (158), robin (152), brown thrasher (125), orchard oriole (120), blue jay (114), catbird (103), mockingbird (77), and flicker (76). The birds of these twelve species made up 80.4 per cent. of the aggregate number belonging to the 52 species found in these farm orchards. It will be seen from the table following that, as in other vegetation areas, the English sparrow decreased rapidly in numbers from north to south, and that both it and the native birds were much more numerous in 1909 than in 1907 (1255 native birds to the square mile in 1907 and 1746 in 1909) ; and this notwithstanding the fact that there were evidently no flocks of gregarious birds to confuse the record in the orchards visited. Although the orchard is, like the open woodland, essentially a field of closely set trees with a ground cover more or less deep and dense according to its treatment, and might hence be supposed to attract the same species of birds in something like the same average number, it is really so different from a forest in the relatively small variety of foods and situations which it offers, and especially in its human environ­ ment, that the two make a widely different appeal to birds. In the comparatively simple orchard, a smaller ·number of species dominate, 13 out of 52 native species comprising 70 per cent. of the whole number; while in the complex forest 20 out of 49 must be taken to make up this 70 per cent. Moreover, a comparison of the corresponding species lists illustrates the wide difference of the two environments, as is shown in the table on page 211. In the first column are the numbers per square mile of birds found in farm orchards, and in the sceond are the numbers • The Orchard Birds of an Illinois Summer, by Stephen A. Forbes and Alfred 0 . Gross. Bul. Nat. Hist. Survey, Vol. XIV, Art. 1, June, 1921. • 210 PRINCIPAL BIRDS PER SQUARE MILE OF ORCHARDS, SUMMERS OF 1907 AND 1909 Southern Central Northern 1907 Quail 289 31 0 15 Mourning dove 297 218 49 310 Flicker 53 187 49 74 Blue jay 114 124 98 14 Orchard oriole 165 0 0 177 Bronzed grackle 137 342 0 192 English sparrow 426 4607 8373 592 Fieltl sparrow 251 62 0 163 Mockingbird 84 93 0 30 Catbird 84 124 49 14 Brown thrasher 84 249 196 118 Robin 145 187 147 148 1909 Both years 327 212 224 256 77 76 J!.72 114 86 120 138 158 2882 2039 206 190 103 77 129 103 129 125 155 152 Total,,s 2129 6224 8961 I 1847 I 4628 I 3622 in woodlands multiplied by 2.14 to compensate for difference in density of the total bird population in orchard and woodland, and thus to make the averages comparable directly. BIRDS IN SHRUBBERY On ninety-three acres of shrubbery, 85 per cent. of it in southern Illinois and nearly all the remainder in the northern part of the state, 154 birds belonging to 35 species were found, a number equivalent to 1056 birds to the square mile. The only especially notable item of the record is the fact that nearly a quarter of these birds were field sparrows (Spizella pusilla) , present in numbers equivalent to 254 to the square mile. Indigo buntings and yellow-breasted chats were each about a third as numerous as the sparrows ; and then came goldfinches ( 55 to the square mile), quail, towhees, cardinals, and Maryland yellow-throats ( each 41 to the mile), blue jays, brown thrashers, and red-headed wood­ peckers ( each 34), bluebirds and cowbirds ( 27 each) , and mourning doves (21), crested flycatchers, crows, meadowlarks, and robins (21 each), making in all as beauti'f ul and interesting a group of birds as we shall find mustered in any one situation. BIRDS OF THE FARMYARD AND GARDEN Five hundred and fifty-seven acres of the area covered by our bird survey were made up of patches of yards and gardens of the farm premises, and on these 2977 birds were identified, a number equiva­ lent to 3418 to the square mile. Here the English sparrow was, of I I 211 COMPARISON OF NUMBERS PER SQUARE MILE OF THE MORE ABUNDANT BIRDS IN ORCHARDS AND IN OPEN WOODS, SUMMERS OF 1907 AND 1909 ( IN ORDER OF NUMBERS IN ORCHARDS) Birds English sparrow Mourning dove Quail Field sparrow Bronzed grackle Robin Brown thrasher Orchard oriole Blue jay Catbird Mockingbird Flicker Red-headed woodpecker Chickadee Crested fly-catcher Indigo bunting Wood pewee Crow Towhee Cardinal Tufted titmouse Redstart Orchard \ Woods (weighted)* 2039 256 212 190 158 152 125 120 116 103 77 76 44 33 16 0 0 0 0 0 0 0 98 109 73 280 98 184 148 24 415 13 0 208 109 109 148 109 135 135 109 98 109 98 * To get the actual numbers per square mile found in woods, divide the numbers of this column by 2.14. course, enormously predominant, making nearly half the total number of birds seen. The bronzed grackle was about half, and the cowbird about a third, as abundant as the sparrow. These three species together averaged 2820 to the square mile, leaving but 598 to the mile for all the other fifty-nine species seen in this situation. If to these three super­ abundant birds we add seven others, of which the robin, meadowlark, flicker, mourning dove, mockingbird, and chimney swift were the most numerous, we shall include 90 per cent. of the whole number of yard and garden birds on our survey list. The record is much distorted, however, by the occurrence in fall of large flocks of blackbirds and cowbirds during the period of their assemblage for migration; but even if we ignore these flocks, the crow­ blackbird still stands next to the sparrow in numbers, although the cowbird drops quite out of the list of the more abundant species. If we omit the sparrows, we have remaining native birds equivalent to 1883 to the square mile, and if we exclude also the flocks of cowbirds and crow-blackbirds as merely aimless visitors which chanced to settle on the trees of the farmyard as a temporary convenience, we have a residue 212 of 1757 birds to the square mile which may be supposed to seek, or at least not obviously to avoid, the companionship of man. WASTE AND FALLOW LANDS Under the heading of waste and fallow lands we have brought together a heterogeneous variety of situations which have in common only the negative character of a lack of growing crops, at least for the year, and the fact that they can not be classified under any of the other vegetation areas of our grouping. These wastes and fallows seem, how­ ever, to make an appeal of their own to a more or less definite group of birds, or to many birds, perhaps, under certain conditions, for we find in them a marked inverse relation, such as we have called attention to in discussing other situations, between the acreage of this habitat in each section of the state and the birds found in it per square mile. The smaller the percentage of waste and fallow land to the general area the greater the density of its bird population, as is seen in the table following: Section Southern Illinois Northern Illinois Central Illinois Acres surveyed 479 147 28 Birds per square mile 708 955 1236 It is perhaps in the central part of the state, where this special kind of surface is smallest, that we shall find among the commonest species those which may be distinguished as birds of the waste lands, and these our MS table shows to be the crow-blackbird (247 to the square mile in that section), red-winged blackbird ( 202), quail ( 202), English sparrow ( 157), field sparrow ( 112) dickcissel ( 112), and Maryland yellow-throat (90). In northern Illinois, it is true, the English sparrow leads the list, and the bobolink staqds next, the sparrow being, in fact, most abundant northward in nearly all situations, and the bobolink confined in Illinois to that part of the state by the limitations of its general range. If, on the other hand, we take the larger area and more numerous observations of southern Illinois as furnishing a better index to the true relations of birds and their environment, we shall find the hetero­ geneous character of wastes and fallows (particularly evident in that section) reflected in the absence of any strongly dominant species or group of species, and the consequent large number of species which we must take into account to include any large majority of the whole num­ ber of birds. Of the 61 species identified on 479 acres of our southern waste and fallow lands, 19 are needed to make only 72 per cent. of our • total number of 804 birds from that situation. First among these more abundant species of southern Illinois stands the meadowlark, with 182 to the square mile for the southern section and 142 for the state at large, averages to be compared with 319 for meadows in southern Illinois and 194 for those of the whole state. 213 Next after the meadowlark comes the red-winged blackbird, (93 to the mile), prominent by reason of its numbers in northern and central Illinois. This is followed by the English sparrow ( 57), much _the least abundant in the southern section, the field sparrow ( 47), mourning dove (37), dickcissel (29), goldfinch and quail (27 each), and ten others in numbers gradually diminishing from 26 to 10 to the square mile. The species are, as a whole, derived from the prairies as repre­ sented in pastures and meadows, with only a minor invasion from forest or marsh. MOST ABUNDANT BIRDS IN WASTE AND FALLOW LANDS, WHOLE STATE, SUMMERS OF 1907 AND 1909 NUMBERS PF.R SQUARE MILE Meadowlark 142' Red-winged blackbird 93 English sparrow 57 Field sparrow 47 Mourning dove 37 Dickcissel 29 Goldfinch 27 Quail 27 Bobolink 26 Bronzed grackle 20 Kingbird 19 Brown thrasher 17 Bluebird 16 Maryland yellow-throat 15 Red-headed woodpecker 13 Blue jay 11 Crow 10 Short-billed marsh wren 10 Total 616 SUMMARY AND DISCUSSION A compact summary of our most general averages of the numbers of our most abundant birds, as found on distinguishable vegetation areas, is given in the following table, an examination of which will enable u! to point out certain conclusions not otherwise readily arrived at. The totals at the bottom of the table show the relative densities of the bird population (both with and without the English sparrow) in the thirteen recognized 5ituations and in the total area of the survey which stands for the state as a whole. 214 THE MORE A BUNDANT SPECIBS IN HABITATS NUMBERS PER SQUARE MILE, WHOLE STATE, S UMMERS OF 1907 AND 1909 Species Englisb sparrow .. . .......... .. ... row-blackbird ........ ...... ... .. . C C M Meadowlark .. . .. . . .. .. .. ...... . .... owbird .... . .... . ... . ... . ....... . .. ourning dove ... . ............. . . .. Dickcissel .. .. ... .. .. .......... ... .. Prairie borned lark ........... ... . Bobolink ... ............ .. ........... F licker .................... . .. .. .... . Red-winged blackbird .. ... . .... . .. Robin . . ................... .. .. . .... ield sparr ow .... . ................. F G oldflncb ...... . ... Red-headed woodpeck.°er :::::::::: Crow . ..... Quail ....... :::::::::::::::: ::::::::: Grassbopper sparrow .. ... . ... . . .. Brown thrasher ................... K "ingbird .. ......... .. .. . ............ Barn swallow ............ . .. . ...... Upland plover .. .. ................. Blue jay .. .. . .. . .. .... . . . ·········· Bluebird . ....... • ..... ............... Killdee r ..... ... . ........ .... ....... Chimn ey swift ... ········· ...... .. Vesper sparrow .... . ..... . ......... Cliff swallow ......... . ....... . ..... Orcbard oriole .. . .................. Indigo bunting .. ...... . .. . ...... .. Mockingbird ... .................. . . Lark sparrow ....... .. .. . ..... . . ... Song sparr ow ...................... Maryland yellow-throat .......... Wood p e wee .... . .. ... .............. Cardinal. . . . .. . . ........... . ...... .. Catbird. ········ ·· · ······ .......... Green beron ... . ................... Downy woodpecker ...... Crested flycatcher . ........... .... . T owhee . .... . ........ ...... ........ Yellow-breasted chat ............. Sbort-billed marsb wren .......... Long-billed marsb wren . .... . ... . Tufted ti tmo use ............ . . ..... . Totals ....... ............. .. . ... . Total native species .......... . Averages of above ........... { d ., ., 00 Is ., ., ba .0 "' 8 Is ., ::, I> d "' ~ ., .... 0 "' en 8 56.53 187 3355 111 2459 82 1947 64 1131 37 746 25 710 24 750 24 6 16 20 920 20 611 20 430 14 389 13 358 12 376 12 315 11 298 10 308 10 310 9 255 8 2 18 7 200 7 197 7 174 6 181 6 174 6 151 6 112 4 116 4 120 4 106 3 93 3 104 3 46 2 54 2 67 2 32 1 27 1 25 1 30 1 20 1 12 1 10 1 18 1 - - .... 793 .. . . 606 .... 18 ... . 14 ;;: ~ ~ .... 'O en ., d ;;: ., en "' Is 0. 0 3 8 B 'O "' ., "' en "' ., "' ;ii: e; ::s P-i rn 94 177 23 57 49 72 207 20 194 151 3 1 142 3 55 0 10 29 41 0 37 100 12 2 29 21 48 0 1 96 24 130 26 31 47 0 7 41 33 1125 93 13 50 8 59 10 28 0 47 7 2 1 15 27 9 26 0 13 13 19 0 10 8 15 76 27 41 9 23 8 6 20 0 17 15 19 0 19 9 23 0 8 25 8 0 0 2 11 . o 11 4 19 0 16 0 12 8 I 12 9 0 11 7 5 0 4 2 9 0 0 1 1 0 4 1 3 8 9 1 6 0 5 1 9 0 8 3 4 38 6 4 5 1~ 15 1 3 1 1 I 0 7 0 2 0 1 2 2 46 1 0 1 0 1 0 1 0 0 0 l 0 0 0 1 0 I 0 0 15 JO 0 0 46 4 0 1 0 0 - - - - 56 1004 I 24 773 762 827 I 01 716 19 22 41 18 17 19 42 16 >, I ., -;::: "' .0 a.i >, Is .; ~ "' .0 ., en d .0 .Cl ~ Is ::, ~ 0 en 0 0 147 163 130 159 56 92 138 4 47 50 9 89 121 II 88 1 141 14 29 40 27 28 5 1 24 5 19 11 4 16 4 23 4 6 10 2 26 21 18 I 3 4 10 8 9 4 5 4 8 10 10 LO 10 5 6 5 21 12 10 11 14 4 6 9 12 5 I 5 9 5 6 I 2 5 6 1 5 8 3 5 2 2 2 5 0 1 2 1 1 I 2 1 0 0 7 0 2 3 2 0 1 3 8 1 2 3 3 12 2 0 I 0 4 2 4 1 1 0 3 0 5 I 3 0 1 1 3 1 4 2 2 0 0 0 0 2 0 0 I 0 0 I I 0 0 0 2 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 68 0 0 0 0 0 0 0 0 0 0 0 0 -- - - - 7 15 488 560 4 3 568 325 430 324 16 11 13 11 13 7 JO 7 - 'O i:: ::, 0 Is be en 'O 'O ., Is ., 'O "' I,; 0 .Cl 0 0 <.) p; ~ Is 0 30 46 2039 28 46 158 21 0 44 49 34 22 77 5 1 256 0 23 11 162 0 0 6 0 0 0 97 76 2 34 11 34 80 152 13 131 190 11 40 38 6 51 44 0 63 5 3 34 212 0 0 0 9 69 125 II gl 27 0 0 34 19~1 0 0 114 15 46 11 58 0 0 4 0 5 13 0 0 0 0 0 0 11 120 0 51 !18 13 0 77 6 0 22 0 0 5 l) 34 3 0 63 5 0 46 38 2 6 103 0 6 5 2 34· 5 0 68 16 0 51 16 0 II 0 0 0 0 0 0 0 0 51 1 33 - - - 609 1471 4026 579 1425 19 7 14 33 92 13 33 45 en i:: ., 'O Is "' ~ >, 'O Is i:: ., "' .0 .0 en ::, 'O Is Is .Cl "' rn >- 0 153 5 5 0 21 27 21 20 0 0 0 0 21 254 55 34 21 41 0 34 0 0 0 34 27 0 0 0 0 14 82 0 0 1 41 0 41 0 0 0 761 5 524 31 6 2 2 1 1 5 1 2 I 2 2 I 2 2 l 2 2 1 36 9 4 4 6 2 3 0 0 1 0 6 3 7 4 8 5 5 3 0 9 5 5 2 5 0 1 0 2 I I 1 0 0 0 21 .. 41 68 0 0 14 - 933 933 21 21 331 177 4 9 5 0 7 4 Arranging these totals in series, we find that orchards stand at the top of both lists and stubble fields at the bottom, the former con- 215 taining nearly nine times as many birds per square mile as the latter if the English sparrows are counted, and about six times as many if they are not. Fields in crops of wheat, rye, barley, oats, or corn, and those from which the small grains have been harvested, are the least attractive to birds of all the situations listed, their numbers of native species per square mile ranging from 324 to 579, while the other areas rise from 716 for waste and fallow to 1987 for orchards. We further notice that our two series do not differ materially in respect to the order of abundance, the dropping out of English sparrows having the effect only to shift six of the habitat names one place up or down, and leaving the positions of seven of the thirteen unchanged. BIRDS PER SQUABE MILE OF 44 OF THE ABUNDANT SPECIBS, THE WHOLE STATE, SUMMERS OF 1907 AND 1909, IN ORDER OF NUMBERS All species Native species Orchards 4026 Orchards 1987 Yards and gardens 3314 Swamps 1801 Swamps 1824 Yards and gardens 1779 Woods 1471 Woods 1425 Pastures 1004 Shrubs 933 Shrubs 933 Pastures 827 Meadows 856 Meadows 762 Waste and fallow 773 Waste and fallow 716 Wheat, rye, barley 715 Plowed ground 579 Plowed ground 609 Wheat, rye, barley 568 Corn 560 Corn 430 Oats 488 Oats 325 Stubble 483 Stubli!e 324 An inspection of our preceding general table (page 214) shows that some birds have but a single favorite haunt or set of closely related haunts, that others have two very different places of principal resort, and that still others have a wide and rather indiscriminate range of local preference. Thus the English sparrow is seen to be mainly a bird of the orchard and the yard and garden; the meadowlark of the meadow, pasture, and waste lands; the dickcissel of the meadow only; the prairie horned lark of pasture fields and plowed ground; the bobolink of swamp and meadow; the field sparrow of shrubbery, orchard, and woods; and other local concentrations within one situation may be readily made out for the blue jay, orchard oriole, indigo bunting, song sparrow, cardinal, catbird, green heron, downy woodpecker, crested fly-catcher, towhee, the two marsh wrens, the red-headed woodpecker, and the mockingbird; while a distinctly double or multiple local allegiance is 216 apparent in our records of the crow-blackbird, found especially abundant in swamps, corn fields, orchards, and yards and gardens, of the cowbird in wheat and yards and gardens, the mourning dove in wheat and orchards, the flicker in meadow, pasture, and woods, and the upland plover in meadow and plowed land. This seems, in most cases at least, mainly a matter of the relations of feeding and breeding places, identical for some birds and for others more or less separate and unlike. If we may assume that the present meadows and woodlands most nearly resemble the primitive prairie and forest as homes and haunts of birds, we see that in bringing the last two under cultivation we have greatly diminished the areas most desirable to birds, and must have reduced the total number of birds accordingly except as these unfavor­ able effects may have been compensated by more favorable conditions established at other points. Such compensation appears in the substitution of pastures for prairie, as may be seen by a comparison of a total of 1004 birds per square mile of pasture with that of 856 for meadow; and in the sub­ stitution of orchard for forest, the numbers of which per square mile (English sparrow excluded) are 1987 and 1425 respectively-gains of 17 per cent. in the first case and nearly 39 per cent. in the second. • By a more detailed comparison of our tabulated data, one habitat column with another, we may get more precise ideas of the apparent affiliation of habitats as related to birds. These affiliations may be inferred from an examination of the following table, made by dropping from each column of the preceding general table the numbers per square mile which are smaller than the general average for the habitat, those remaining showing the species which are equal to or greater than the habitat average for all the species. It will be readily seen that this table is divisible vertically into three more or less definite areas or bands, made up respectively of (1) meadows, pastures, swamps, and waste and fallow lands, the nearest approach remaining to us ot the primitive prairies of the state; (2) fields of cereal crops together with plowed and stubble fields which have lately borne them; and (3) areas of forest, orchard, and shrubbery to which the exceptionally and radically new habitat of yards and gardens may be appended as more nearly related here than anywhere else.* For convenience' sake these may be distinguished as pasture­ meadow, cereal-crop, and tree-shrub associations; and the numbers of birds per square mile of each were as follows: cereal-crop, 602, pasture­ meadow, 923, and tree-shrub, 3111, related to each other respectively as. 1, 1.65, and 5.17. By a more detailed comparison of our tabulated data, one habitat column with another, we may get more precise ideas of the apparent affiliation of habitats as related to birds. The cereal-crop area is evidently • F or m or e s ignificant ~tw of this relationship, see the detailed general t able oi. .Ute ""?cslt,e page.,;;,, ri 217 CONDENSED GENERAL TABLE WITH SUBSTITUTION OF AN ASTERISK FOR ALL NUMBmRS LESS THAN THE AVERAGE OF ALL BIRDS FOR THlD HABITAT Species English sparrow . .. . .. . .. . ... .... .. .. ..... . Bronzed grackle . . .... . .... . ..... . ....... . . . Meadowlark .... . ......... .. ... . . . .... . ..... . Cowbird . . ... . . .... ................ .. .. . .... . Mourning dove ................... . .... .. ... . Dickcissel .. .... ... . . .. .. ... ... . . .. ..... . .. .. . Prairie horned lark. . . . . . . .. .. ..... . ... .. . Bobolink ........................ ... ... .. ... . Flicker . ..... ... ... . .. . . . ........ . . .. . . ..... . Red.winged blackbird .... . . . . . . . ....... . .. . Robin ....... . . ... . . . .. .. .... . .. . . . .... . .... . . Field sparrow ...... . ...... ... . .... .. .. . . . . . . Goldfinch .... .. ..... .. .. .. . .. . ..... . .. . .. ... . Red-beaded woodpecker .......... . ........ . Crow .. .. .. . ............. ..... .............. .. . Quail. . . ... .. . ............ . ...... .. ......... . . Grassb.opper sparrow ............... .. .... . Brown tbras.ber . . .. . .... . .. . ........ . . .... . Kingbird ...... . .......... .. ..... . ..... .. . . .. . Barn swallow .. ... . .. ... ..... .. . ....... . . . .. . Upland plover .. . ... . .. .. . ....... . ....... . .. . Blue jay ............... .. ............. . .... . . . Bluebird .. ... . .... . .. . .. .. . .. . . ... .. .. .. .. . . . Killdeer ................ . . .. .... . .. .. . .. ... . . . Chimney swift. ........ . ..... . . . ..... . ... . ,. . Vesper sparrow .. . .... .. ......... . Cliff swallow .... . .. . ... . ..... . ........ . .... . Orchard oriole ...... .. ..... . . .... . . .. .. . ... . Indigo bunting ............. .. . . . . ...... . .. . . Mockingbird . .. .. . ......... . ... . .... . . . .... . Lark sparrow .. .. .. ...... .... . .. ......... .. . Song sparrow ............. . .. ... ........... . Maryland yellow-throat .. .. .. . , . ... .. .. . .. . Wood pewee ....... . .. . . .. ........ ... .. .. . . Cardinal. ... . . .. . . .. ..... . .... .. .... . .. . .... . Catbird .. . . .. .. .. . ...... . . . .. .. . ..... . . .. . .. . Green beron . ......... ... . .. .. . . .. . . . . .. . . . . Downy woodpecker ., . .. . . . . . . ...... . . . ... . Crested flycatcher .... .. ... .. ... . .. . ..... . Towhee ............ .. . . ...... . .. . . . . . . . ... .. . Yellow-breasted cbat ..... . ..... . .... .... . . Short-billed marsb wren . . .... .. .. . .. . .. . . Long-billed marsb wren ... .. . . . . .. .. ...... . Tufted titmouse .. .... ... .... . ..... . ... . . .. . "' I!= 0 'Cl "' Q) ::s ., 0, s "' I!= C/J 94 177 • 57 49 72 207 20 194 151 • 142 • 55 0 • 29 41 0 37 100 • • 29 21 48 0 • 96 2' 130 26 31 47 0 • 41 331125 93 • 50 .'59 • 2ll O 47 147 56 47 121 141 27 r/J .... "' 0 163 92 50 II 14 28 24 • • 16 • • 26 21 • * • • • 27 • • • • ,. • %6 0 • • • • 0 • 21 • • 76 27 41 • • • • • 0 • • • 0 19 • 23 0 • 25 ,. 0 0 • ... 0 • • • 0 • 0 • ,. • • • 0 • • • 0 * • • 0 0 • • 0 • • * • • • ,. 0 * • • 0 * • • • • • • * • • • • • • • 0 • 0 • 0 • • • 46 • 0 • 0 • 0 • 0 0 0 • 0 0 0 • 0 • 0 0 ,. • 0 0 46 • 0 • 0 0 • • • • ,. • 0 * 0 • • • • • • • • 0 0 0 0 0 0 0 0 0 0 0 12 • • • • • • • • 0 • * • 0 • 0 • • • 0 0 • 0 0 0 0 0 0 0 0 ~ ... 0 0 "' 'Cl 0 0 ~ 130 159 30 46 2039 0 1535 138 * 28 46 158 0 761 • 89 21 0 ,. 21 ,. 88 • 49 34 • 27 524 29 40 77 51 256 21 * * * 0 • • • * 19 11 162 0 0 0 • * 23 • 0 0 0 • • • 0 97 • 0 • 18 • ,. 34 * 0 • • • 34 80 152 21 ,. • • • 131 190 254 • ,. • • 40 ,. 55 • * • • 51 * 34 • • 11 0 63 • 21 • • * * 34 212 41 • * * 0 0 0 0 0 * * ,. 69 125 34 ,. ,. * • 0 ,. 0 ,. * * 0 0 0 0 ,. ,..34000,. ,. ,. 0 194 114 34 ,. ,. * 15 46 • S7 • ,.osaooo,. • 0 • 0 • 0 ,. * • • 0 0 0 ,. • 12 0 0 0 0 ,. • 0 0 * 120 * • * * 0 51 • 82 0 • 0 • 0 • 0 ,. • 0 * 0 • 0 • • * 0 0 • * * * 0 0 34 • 41 * 0,.053,.0,. * 0 0 46 • 41 0 • 0 * ,. 103 0 * • 0 0 • • 0 0 .0,.34 ,. 0,. 0 * 0 t18 * 21 * 0 0 0 51 • 41 * 068 0,.068,o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 51 • * 0 Averages...... ..... .. . ...... ......... .. . 19 22 41 . 18 16 11 13 11 14 33 92 21 75 a derivative of the pasture-meadow association, differentiated to the advantage of the former, but to the detriment of the birds; and the ornithological preponderance of the tree-shrub association may be more clearly shown by a comparison with the first two associations thrown together as one, g1vmg us an average of 762 birds per square mile for the combination against 3111 for the tree-shrub association. Otherwise stated, we have found the summer-time birds" of Illinois more than • 218 four times as abundant to the unit of area in the tree-shrub association as in the remainder of the state. In this connection, however, we must recall the fact that the woodland area of our survey is not the dense and full grown forest of the wilderness, but is rather to be taken as equivalent to the forest edge; and the further fact that the limited acreage of our tree-shrub formation, 880 acres in all as against 18,408 of the other habitats, has probably led to a certain concentration of the normal forest birds, and especially of those which nest in trees and shrubs and seek their food largely in the open fields. As a most general outcome of this final discussion, we may con­ clude that the remaining birds of the Illinois wilderness have adapted themselves to civilization, and especially to agriculture and horticulture, not so much by a change of choice or of habits, as by searching out under the new conditions the places which most nearly resemble their original nesting sites and which offer them food the nearest to that which, by hereditary inclination, they were impelled to choose; that in pastures, orchards, and yards and gardens they have found situations more favorable, and in the vast areas devoted to the cereal crops less favorable, to their maintenance and multiplication than their original habitats; and that while certain species have suffered heavily, in some cases nearly or quite to extermination (mainly, however, by the deliberate acts of man), others have greatly increased in numbers, the numerical make-up of the bird population of the state having thus shifted its balance in response to an increase of some resources and a diminution of others. Their remarkable succe~s in self-maintenance under changes of environment which, from their viewpoint, may be called revolutionary, is not due to any flexibility of organization and consequent power of physical adaptation to new conditions-for which, indeed, they are much too highly and rigidly specialized-but to their remarkable sensory endowment and unequaled powers of locomotion, by the use of which each species is enabled to search out and occupy the most satisfactory ecological situations still to be found in the area of its geographical dis­ tribution·. PLATE XXXV Southern Illinois landscape near Cave in Rock, Hardin county. On the Ohio River-indistinctly seen at the extreme left. PLATE XXXVI Typical view in farming area of southern Illinois, Hardin county. PLATE XXXVII Typical central Illinois pasture near Ogden, Champaign county. Upland plovers in this field. PLATE XXXVIII Boggy pasture, characteristic of lowland fi elds n ear marshes in northern Illinois. Libertyville. Lake county. PLATE XXXIX Clover field, cut a nd pastured . near Midland City, D ewitt county, central Illinois, July 16, 1907. Containing r e d-winged blackbirds, robin, upland plovers, m eadowlarks, prairie horne d larks, and brown thrasher. PLATE XL M eadowlark, from life, April 1, 1907. n ear Bismarck, V e rmilion county, central Illinois. PLATE XLI Meadowlark's nest with two eggs of the m eadowlark and three of the cowbird, Urbana, Champaign county, central Illinois, May 20, 1908. PLATE XLII Meadowlark's nest and young, near Benton, Franklin county, southern Illinois, June 11, 1907. PLATE XLIII Meadowlark's nest and eggs, near Easton, Mason county, central Illinois, May 1, 1907. PLATE XLIV Meadowlark's nest and eggs, n ear Urbana, Champaign county, central Illinois, May 30, 1907. • • PLATE XLV Meadowlark's nest and eggs, near Elkville, J::i,ckson county, southern Illinois, June 21, 1907 . • PLATE XLVI Meadowlark's nest and eggs, near Clinton, Dewitt county, central Illinois, May 16, 1907. • PLATE XLVII Nest and eggs of prairie-hen, near Clinton, Dewitt county, central Illinois. A few yards from nest of meadowlark shown in preceding picture. PLATE XL VIII Typical oats fie ld, L ee county, northern Illinois. August 7, 1907. PLATE XLIX Wheat field near Emery, Maoon county, central Illinois. July 18, 1907. .. PLATE L Nest and eggs of red-winged blackbird, July, 1909 . ... PLATE LI N e st and eggs of red-winged blackbird. in timothy meadow near Benton, Franklin county, southern Illinois, June 4, 1907. PLATE LII Nest and four eggs of grasshQpper sparrow in alfalfa field, Urbana, Champaign county, central Illinois, May 27, 1907. PLATE LIII Typical Illinois corn field near Buffalo Hart, Sangamon county, central Illinois, July 24, 1907 . • PLATE LI\' Nest and eggs of prairie horned lark in oats field near Ogden, Champaign county, central Illinois, l\iay 28, 1907 . • PLATE LV Marsh nea r Davis Junction, Ogle county, northe rn Illinois, July 30, 1907. Home of the s hort-bille d marsh wren-of which young birds were seen at this date. Bobolinks a nd r ed-winged b lackbirds common h ere. • --' .- •• 1 :..-c:t PLATE LVI . ' Tamarack swamp near Wauconda, Lake county, northern Illinois, March 4, 1907. PLATE LVII "\Voodland forest n ear Mulkeytown. Franklin county, southern Illinois, June 20, 1907. Wood thrus h and towhee common. Great crested fly-catcher, yellow-bellied cuckoo, cardinal, red-bellied woodpecker, and tufted titmouse seen here. PLATE LVIII Bur oak woodland near Poplar City, Mason county, central Illinois, May 2, 1907. Prickly pears on the sandy soil. Field sparrow and towhee here. PLATE LIX L owla nd forest nea r Cave in Roc k , Hardin county, southe rn Illinois, July 1, 1907. Wood thrus h a nd r ed-eyed vireo v e ry common here. PLATE LX Mourning dove's nest and eggs, near Thompsonville, Franklin county, southern Illinois, June 6, 1907 . • PLATE LXI Mourning dove's n est and eggs, near Mount Vernon, Jefferson county, southern Illinois, June 14, 1907. • PLATE LXII Mourning dove's eggs in old robin's nest, Olney, Richland county, southern Illinois, September 7, 1908. PLATE LXIII M ourning dove's nest a nd eggs near center of la rge corn fi eld, July 16, 1907. PLATE LXIV l\11ourning dove 's n est and two young, n ear M ount V ernon , J e ffer son county, southern Illinois , June 14, 1907. PLATE LXV Shrubbery n ear Clinton , D e witt county, central Illinois, April 26, 1907. PLATE LXVI Sassafras thicket near Golconda, Pope county, southern Illinois, June 28, 1907. Prevalent condition throughout this county. Maryland yellow-throat, indigo bun ting, and field sparrow very common. Two adults and three young of Kentucky warbler seen in woods near by. PLATE LXVII Open woods and shrubbery n ear Mt. Carmel, Wabash county, southern Illinois, April 9, 1907. Near the limit of density permitting the counting of birds. PLATE LXVIII Old corn field near Farmer City, Dewitt county, central Illinois, March 29, 1907. Prairie-hens flushed in this field, and two mallard ducks arose near by. PLATE LXIX Southern Illinois f a llow, ,June, 1909. PLATE LXX Fallow field near Tamaroa. Perry county, southern Illinois, June 19, 1907. Meadowlarks abundant, two of their nests with eggs and one with young found within fifty yards of each other.