Veny) Weta eh KR raises ASANR AY hn PAAR? Ny baka Set * ~ , me meth eee eee ihe +h > ‘ As hee Spasoiabens Ay kows eos tee — * mere papa av'4 wie Pam Moete! ters NR oy haber lindnend ie as ert A hua a Nowe teary Riaewee Peden ts cea eee ee Stet trees —~ naleete dep ms eet ter aon op lene eto ey ar? ‘5d a vedo tone Pi dnee moka Cie fn 1 wreray a peed iw trtlita ral bk CS OR LSAT rst, peut ui Oe Ase abn tie Pade rtf = % lat Rica ah relia mang Stee eee — beads veds) As eer on red we Fe putd spy ee row ain OGY A Pe? i} Hens yarn) tir. LIBRARY OF THE UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN NOTICE: According to Sec. 19 (a) of the University Statutes, all books and other library materials acquired in any man- ner by the University belong to the University Library. When this item is no longer needed by the department, it should be returned to the Acquisition Department, University Library. ILLINOIS NATURAL HISTORY SURVEY a) ILLINOIS BIRDS: VIREOS Jean W. Graber, Richard R. Graber, and Ethelyn L. Kirk Illinois Natural History Survey Champaign, Illinois - August 1985 State of Illinois ; \ Department of Energy and Natural Resources ' — Natural History Survey Division - Biological Notes No. 124 ae Illinois Birds: Vireos Jean W. Graber, Richard R. Graber, and Ethelyn L. Kirk This paper, the tenth in a series on Illinois birds, concerns the vireos (Vireonidae). Seven species of the family occur in Illinois, one—the Philadelphia—only as a transient in spring and fall. Another species—the solitary vireo—has been found nesting only at Sand Ridge State Forest (Bjorklund 1979-1980, 1980-1981) and occurs in the state primarily as a transient. The other five species nest regularly in Illinois and occur also as migrants. All previous papers in this series have followed the nomenclature and order of species in the 5th edition of the American Ornithologists’ Union's (1957) Check-list of North American Birds. This paper follows, as a matter of course, the recently published 6th (1983) edition of the Check-list. The emphasis in our papers is on populations of birds, not their taxonomy, though we recognize that nearly any, and perhaps all, aspects of a species’ biology may relate to its taxonomy. In most respects the methods and policies applied in this paper are the same as those in previous papers of the series—most notably in Graber et al. 1970, 1977, and 1983. Where no authority 1s cited for a record, the record is ours. Sexual dimorphism in plumage is essentially lacking in vireos, and references to sex in our field observations are based on behavior—especially sus- tained singing by the birds observed. Because many of the measurements included in this paper—especially those from the older literature—were made in English units, we initially (1983) elected not to make conversions to metric, but after further considera- tion decided to present both—the English and the met- ric equivalent following in parentheses. Exceptions are bird weights (grams only) and bird population figures in tables, given as birds per 40.5 ha (= birds per 100 acres). We have used abbreviations for the regions referred to in the tables, i.e., N for north, C for central, and S for south. The regions are shown in Fig. 4. As always, we are indebted to Marilyn Campbell and her colleagues at the Vermilion County Conserva- This paper is published by authority of the State of Illinois and is a contribution from the Section of Wildlife Research of the Ilinois Natural History Survey. Dr. Jean W. Graber and Dr. Richard R Graber were, until their retirement in 1983, Wildlife Specialists, and the late Miss Ethelyn L. Kirk served as a technical Assistant in the Section of Wildlife Research Two or more outside referees recommend each manuscript sub- mitted for publication in the Biological Notes series before it is accepted. Correct citation: Graber, J.W., R.R. Graber, and E.L. Kirk. 1985. Illinois Birds: Vireos Illinois Natural History Survey Biological Notes 124 tion District and the Vermilion County Audubon So- ciety, not only for contributions of data, but for their sustained encouragement. H. David Bohlen of the Illi- nois State Museum gave us copies of his extensive notes on central Illinois birds and checked the original manu- script for errors. We are also indebted to members of the Champaign County Audubon Society for numerous nest records, and to Earl Long particularly for his counts of birds in an intensively cultivated area of cen- tral Illinois. Leroy Harrison of Olney generously shared with us his unpublished data on bird kills at a southern Illinois television tower. Before his studies, the only data available on tower kills for the entire southern region were those of Heye (1963) for Cape Girardeau. Dr. Richard Bjorklund of Bradley University kindly provided current information on the nesting of the soli- tary vireo and gave us permission to use his photograph — of the nesting bird. Bowie Hannah of Texico gave us a number of nest records and gave us permission to copy her slide of a yellow-throated vireo at its nest. Dr. Barrie Hunt of Eastern Illinois University shared with us his records on vireos in Illinois and reviewed the original manuscript. Our colleagues at the Illinois Natural History Sur- vey provided essential help in many ways with charac- teristic high efficiency and excellence. We are especially indebted to Dr. Glen C. Sanderson not only for his | detailed editing of the manuscript, but for his con- tinued support and encouragement of our studies on Illinois birds. This paper also benefited greatly from the questions and comments of Dr. Scott Robinson and Dr. Richard E. Warner. WHITE-EYED VIREO (Vireo griseus) (Fig. 1) Spring Migration The earliest records of white-eyed vireos in Illinois were 2 April in southern and central Illinois (Fig. 2; Silloway 1906; Kleen 1976c) and 7 April in the north (Smith & Du Mont 1944a). Peak numbers have been seen 21 April-8 May in the south (20-45 per day), 2-17 May in the central region (8-12 per day), and 8-31 May in the north (3-6 per day). Musselman’s (1913) count of 24 white-eyes at Quincy on 4 May 1912 (not shown) exceeds recent counts for central Illinois and indicates a large population for that early period. A white-eye killed by a storm over Lake Michigan on 16 April (Segal 1960) and one killed at the Olney tower on 16 May (L. / August 1985 GRABER, GRABER, & KIRK ILLINOIS BIRDS: VIREOS .. fv! Fig. 1.—White-eyed vireo at its nest, 1] June 1973, in Pope County Harrison unpublished 1978) indicate active nocturnal migration on those dates. Spring populations, like the breeding populations, were highest in forest-edge and shrub habitat; no other habitat approached its importance (Tables | and 2) Spring densities were, on average, only slightly higher than June densities in both southern and central Ilinois—not surprisingly, as the range does not extend much north of Illinois (Fig. 3). The numerous pub lished spring (vs other seasons) records may represent overmigration or merely a special Conspicuousness in spring because of the song. Turn-ol-the-century counts (unpublished) of white-eyes by Frank Smith and his University of Illinois students in east-central Illinois were low (usually only one per day) by comparison with our more recent counts Distribution White-eyed vireos probably nest in every county in Illinois, but the population in the northern region ts sull low, notwithstanding nest records there that date back into the last century (Fig. 4). Barnes (1890) consi dered the white-eye rare in Marshall County, where it ts sull uncommon, although Ferry found it common at Henry (Cory 1909). The same indication of a fluctuat ing population in northern I]linois is given by Mundt (1883). Strangely, old records are lacking for the Missis sipp! valley north of Quincy. This species has made occasional population exten- sions northward, but has apparently been unable to sus tain them in the past century. Whether recent apparent increases in the north (Bohlen 1978) will last, remains to be seen. The sustaining populations have been and suill are on the forest soils of the southern half of the Stale In addition to breeding records plotted in Fig. 4, there are records for unspecified localities in McLean County (Kleen 1974c); Will, Warren, Kane, and Hen derson counties (Kleen 1979-1980, 1980-1981); and Peo Loucks unpublished 1890 ria and Tazewell counties 1892 Nesting Habitats and Populations White-eyed vireos have never adapted to humans historically), they remained on the outskirts Rideway 1887 I he Even early nesting habitat has precisely —quantitatively—but has of the village not been defined been described as hazel thickets and brier patches tangled copse ind brushy swamps (Ridgway 1889 4 ILLINOIS NATURAL HISTORY SURVEY BIOLOGICAL NOTES 10 NORTH NE! JUN O O CENTRAL O fe) O| EGG DATES, 10 APR MAY UN 4 o O SOUTH BIRDS COUNTED PER DAY 20 O poe EGG LAYING (SPAN OF DATES) 12 24 JUL AUG JUL AUG OO— EGG LAYING (SPAN OF DATES 12245, a2, 28 12 24 APR MAY JUN TV KILLS . ) 468 0 12 24 12 24 2 24406 Ulf JUL AUG SEP OCT Fig. 2.—Egg-laying and migration seasons of the white-eyed vireo in different regions of Illinois. Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Shaded areas show the span of dates during which eggs or laying have been recorded. The dash line shows numbers killed at television towers in southern Ilinois during migration. 1923), and along the Mississippi near Keokuk, as wet, heavily umbered bottomland (Du Mont 1936). Our cen- suses indicate that forest habitat proper supports only modest numbers—more in bottomland than in upland (Table 2). On a strip-mined area white-eyes did not appear unul 18-20 years after mining was stopped (Brewer 1958). Kendeigh (1982) found that white-eyed vireos in east-central Illinois did not reach peak num- bers on abandoned farm land until 44 years after culu- vation ceased. White-eyes favor the late successional stages, In contrast to Bell’s vireo, the other common shrub vireo. Lowland shrub areas may be the most pre- ferred habitat of the white-eye (Brewer & Hardy 1950; Table 2). ur August 1985 GRABER, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS Tasce 1.—Spring and fall population densities of the white-eyed vireo in various Illinois habitats (1979-1981). County Number Cumulative . or of Hectares Birds per 40.5 ha Season and Habitat Region Censuses Censused Maximum Mean Spring (3 April-28 May) Mature bottomland forest Piatt (C) 8 166 2.0 0.2 Mature bottomland forest Johnson (S) 21 436 13.1 2.8 Mature upland forest Piatt (C) 10 220 0 Mature upland forest Pope (S) 23 154 9.6 04 Forest edge and shrub Piatt (C) 9 183 8.9 3.8 Forest edge and shrub Pope (S) 19 375 35.2 13.2 Loblolly pines Pope (S) 12 214 2.4 0.2 Fall (1 August—12 October) Mature bottomland forest Piatt (C) 21 425 2.0 0.1 Mature bottomland forest Johnson (S) 21 419 7.7 2.3 Mature upland forest Piatt (C) 26 506 te 0.1 Mature upland forest Pope (S) 18 370 1.9 0.2 Forest edge and shrub Piatt (C) 26 189 22.2 5.0 Forest edge and shrub Pope (S) 20 407 18.0 6.9 Loblolly pines (1979-1980 only) Pope (S) 10 177 0 Tas.e 2.—Breeding populations of the white-eyed vireo in various Illinois habitats. Birds per County or Hectares Type of Habitat 40.5 ha Years Region Censused Census Reference Abandoned farmland 0-24 1946-1971 Piatt (C) 18-24 Map Kendeigh 1982 (shrub and forest edge) (avg 7.9) (25 years) Shrub and forest edge 0-6.3 1980-1981 Piatt (C) 38" Surip This paper (avg 3.2) Forest (all types, including 4-10 1957-1958 South 138 Suip Graber & Graber 1963 edge) (avg 2.4) Bottomland forest 0-12.6 1973-1981 South 1,129 Suip This paper (avg 2.3) Floodplain forest +> 198] Wayne (S) 8 Map Keener 198]a Upland forest 04.2 1974-1981 South 623 Suip This paper (avg 1.4) Swamp and thicket 15.4 1950 Jackson (S) 5 Map Brewer & Hardy 1950 Shrub, including edge shrub 2-H 1907-1909 South 23 Strip Graber & Graber 1963 (avg 3.6) Shrub, including edge shrub Is 1957--1958 South 52 Strip Graber & Graber 1963 (avg 3.1) Shrub and forest edge 9.3-14.4 1979-1981 Pope (S) 62 Suip This paper (avg 12.4) “Strip censuses calculated as cumulative hectares. b+ = Jess than one bird per 40.5 ha. Comparative censuses indicated no noteworthy The causes of variation in wild populations need long- change in the white-eye population between 1907 and term study. 1957 (Table 2), though Ridgway (1915b) noted a decline Territory sizes of white-eyed vireos varied from 0.33 in southern Illinois. The higher densities in 1979-1981 acre (0.13 ha) in swamp thicket in southern Illinois suggest a recent increase, but may only reflect annual (Brewer 1955) to 3.45 acres (1.40 ha) in forest edge in variation or habitat quality on a particular study area. central Illinois (Hensley 1948). 6 ILLINOIS NATURAL HISTORY SURVEY BIOLOGICAL NOTES eam 5 os eg cna ey et fete make Wh Vireo “= : E pea | | Die | 4; e Ranges | f |] BREEDING EE winter 2100 600 600 _ =a mulen Dept of Geography -Univ of Iihnors 0" 100% vor L Fig. 3.—General distribution of the white-eyed vireo. Our list of plants recorded as sites of 36 white-eyed vireo nests is notably diverse: sugar maple (Acer saccha- rum), red buckeye (Aesculus discolor), river birch (Bet- ula nigra), blue beech (Carpinus caroliniana), flower- ing dogwood (Cornus florida), hazel (Corylus americana), hawthorn (Crataegus sp), persimmon (Dzo- spyros virginiana), red cedar (Juniperus virginiana), spicebush (Lindera benzoin), ironwood (Ostrya virgini- ana), cherry (Prunus sp), shingle oak (Quercus imbrica- ria), multiflora rose (Rosa multiflora), poison ivy (Rhus radicans), sassafras (Sassafras albidum), buckbrush (Sym- phoricarpos orbiculatus), and winged elm (Ulmus alata). The list refers mainly to southern Illinois and is undoubtedly far from complete. No plant dominated strongly, but winged elm was somewhat more com- monly used in the south, and multiflora rose in the central region. The heights of 39 nests ranged from 1.0 to 6.0 feet (0.3-1.8 m), with a mean of 2.5 feet (0.8 m). Nesting Cycle Ridgway (1873), Ferry (1907), and Farwell (1919), provided phonetic interpretations of the white-eyed vireo’s distinctive song. Ridgway’s was “‘chick’ty-beaver, limber stick,’ with emphasis on the first syllable of each word (Butler 1891). Singing continues to the end of September in the south, where we have heard courtship song as late as 29 August. The common alarm note— No. 124 White-eyed Vireo BREEDING RECORDS en ae NESTS OR YOUNG @= 1950- A= 1900-1949 @= Before 1900 JUNE RECORDS o= 1950- A= 1900-1949 O= Before 1900 Fig. 4.—Breeding records of the white-eyed vireo in Illinois. Heavy lines show the limits of the three regions referred to in the text. ‘“chek-chek-chek’’—repeated over and over, sometimes for a minute or more, is heard especially often in late August and September, possibly because young birds are present. During April at least, the male is persistent in his courtship, following the female in flights through the shrubbery and from branch to branch, where he may perch a few inches in front of her and weave from side to side while singing a complicated, soft, bubbly court- ship song. He accompanies her during the search for a nest site, and during building, brings some material. We have seldom found “male nests’ of the white-eye of the sort so common among Bell's vireos. Perhaps there is a more balanced sex ratio among white-eyes, Or perhaps male white-eyes do not often attempt such structures, August 1985 GRABER, GRABER, & KIRK Fig 1973 June At one nest that we observed (Fig. 5), the singing tale attempted repeatedly, without success. to attach nall dried, disc-shaped fungi to the outside of the nest fest material often includes the bark of cedar and river irch. Green moss is included in manv nests, especially n the rim, in such a way as to suggest decoration. Thin bbons of birch bark on the outside of many nests ive the appearance of decoration pear whitish externally. They are often placed near le center of a shrub or thicket Building in extreme southern Illinois often be gins Out 20 April. One pair started a nest on 21 \pril, then also The nests generally 5.—A white-eyed vireo on its nest ILUNOIS BiRDS: ViREOS in Pope County abandoned it for reasons unknown, anc pleted (except for the lining) 1 largely com a second nest just 2 feet away by the afternoon of 24 April. Another pair put the and moss decoration on their nest between 1000 1600 CS] May. Construction of early nests probably requires about 3-4 days lining and on 5 \t four nests where we saw both nest construction and the onset of laying the delays in laying from the end of building were 1, and 5 days—delays that would seem to invite cowbird (Molothrus ater) parasitism The eggs are white and lightly speckled with brown The laying season extends from at least 27 April to 24 8 ILLINOIS NATURAL HistoRY SURVEY BIOLOGICAL NOTES June in the south (Fig. 2), where the dates, especially the late date, will likely be extended when more data are available. Data for the central and northern regions are even more incomplete. Cowbird interference at nests of white-eyed vireos has complicated the acquisition of data on clutch size. Ten of 12 recent white-eye nests that reached the laying stage in Pope County were parasitized. The two unpar- asitized nests held three and four eggs. The parasitized nests had ultimate (highest seen) “‘clutches’”’—host and cowbird—of 4 and 2, 4and 1, 4and 1, 3 and 3, 3 and 2, 3 and 2, 3 and 1, 3 and 1, 3 and 1, and | and | eggs. In the sample of nest records (10) available for northern and central Illinois (mainly pre-1947), none was parasitized, and four-egg clutches (7 of 10) predominated. Three- egg clutches of this group were found after 9 June; the earlier season sets had four eggs each. The incubation period at one Pope County nest was 15 days from the laying of the third egg to its hatching. Both adults take part in incubation. The duration of nestling life apparently has not been determined. Nesting success in our small sample (12) of nests in Pope County was nil mainly because of cowbird inter- ference, but a larger sample of nests is needed to under- stand rates of success and productivity. Present data indicate that this population could not sustain itself. We sometimes see (brown-eyed) young of this species 1n late summer; counts of these birds and the (white-eyed) adults should provide a good measure of productivity for particular populations. The laying season is suffi- ciently long in the south to indicate that more than one brood could be attempted, but studies of banded birds are required to determine the number of broods reared. The long laying period may actually be related primar- ily toa high failure rate in nesting. Many white-eyes are conspicuously in molt during August and early September in southern and central Illinois. We have seen birds in fresh plumage as early as 4 September and at least one still in molt on 24 September. Fall Migration As in virtually all southern-ranging species, the white-eyed vireo’s fall migration is rather obscure (Fig. 2). High counts of 6-13 in the period 27 August—l4 September in central Illinois, and of 17-22 in southern Illinois, 21 August—-18 September (Fig. 2), may indicate the peaks of the fall flights. Single specimens killed at the Cape Girardeau television tower on 29 September and 6 October (Heye 1963) indicate active migration on those dates. White-eyed vireos have been seen as late as 14 October at St. Louis (Cooke 1909), 20 October in the central region (Kleen 1979b), and 9 October in the north (Brodkorb 1926). A white-eye at Chicago on 17-18 December 1982 (Kleen 1983) was surely an abnormal occurrence. The ratio of our counts of white-eyed vireos—spring to fall—was 6.6 to 1.0 in east-central and 2.2 to 1.0 in west-central I]linois. The more precise transect censuses No. 124 showed a ratio of 1.0 to 1.3 in east-central Illinois. In southern I]linois the ratio was 2.7 to 1.0 (2.2 to 1.0 in the transects). The high ratio probably relates to the species’ conspicuousness in spring, but could also represent overmigration. As in spring, densities of the fall population were highest in the nesting habitat—forest edge and shrub (Table 1)—but fall densities were consistently below spring and summer densities in all habitats. Food None of the excellent studies we have seen on the food of the white-eyed vireo (Chapin 1925; Nolan & Wooldridge 1962) includes specific data for Illinois, but the general patterns observed in all (e.g., the high inci- dence of Lepidoptera in the diet) probably apply to Illinois as well. Nolan’s observations in southern Indi- ana should be especially pertinent. Our only observa- tion on the subject was of a white-eye that held a sul- | phur butterfly (Colas philodice) in its feet as it ate the | body piece by piece. Specimen Data George (1973) concluded that young white-eyed vireos typically replace all major flight feathers during juvenile life, but that in certain midwestern popula- tions, juveniles retain some or even all of the flight feathers until the post-nuptial molt. He also pointed out that wing area in juveniles is much smaller than in adults, i.e., that wing loading is unfavorable in juve- niles. The breeding population of white-eyes in I]linois is believed to represent Vireo griseus noveboracensis (American Ornithologists’ Union 1957). BELL’S VIREO (Vireo bellii) (Fig. 6) Spring Migration Bell's is probably the most inconspicuous of the Illinois vireos. Except for singing males, it may go largely undetected, and our counts are probably low in comparison with those for other species. Bell’s vireos are not usually detected away from their nesting areas in shrub habitat. Bell’s is usually the last of the vireos to arrive in spring (Widmann 1907). The earliest reports in or near Illinois were 20 April in the south (Ridgway 1925a), 16 and 19 April in the St. Louis area (Comfort 1942), 27 and 28 April in the central region (Cooke 1888; Bohlen unpublished 1976), and 24 April in the north (Fawks 1966). High counts anywhere in the state have been less than 10 birds per day (Fig. 7), with peak numbers seen 11-28 May in the south, 17-24 May in central Illinois, and 24-31 May in the north. | | { ] ’ August 1985 : ras GRABER, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS y Fig. 6.—Pair of Bell's vireos at their nest (A, the female; B, somewhat worn male, which sang regularly on the nest), 14 June 1984 at Rend Lake. [he counts of Frank Smith and his students in east- central Illinois earlier in the century were low (only one per day) by comparison with our counts. Distribution Illinois lies near the northeastern edge of Bell's vireo’s range (Fig. 8). We would expect the species to nest in all Illinois counties, but it is generally absent from upland shrub areas in the Shawnee Hills of extreme southern Illinois (Fig. 9), where white-eyed vireos are abundant. Bell's may ultimately be found in bottomland shrub areas in these counties, however. The absence of records in many of the more northern coun ties (Fig 9), where the species occupies both upland and bottomland shrub areas, probably reflects only insuffi cient exploration of those areas. In addition to records plotted in Fig. 9, there are breeding records for unspeci fied localities in Mercer County (USNM #26897); Taze well and Peoria counties (Loucks unpublished 1892 1894); McLean, Hancock, Monroe, and Randolph coun ties (Kleen 1976-1977); Richland, Lawrence, and Madison counties (Kleen 1979-1980); and Rock Island County and eastern Will County (Kleen 1982 10 ILLINOIS NATURAL History SURVEY BIOLOGICAL NOTES NORTH 10 O 10 CENTRAL 1224 20 APR JUN BIRDS COUNTED PER DAY SOUTH No. 124 EGG LAYING (SPAN OF DATES) 12 24 OCT EGG LAYING (SPAN OF DATES) 12 24 OCT EGG LAYING (SPAN OF DATES) 10 12° 24 APR MAY JUN 12 24 SEP 12 24 JUL OCT AUG Fig. 7.—Egg-laying and migration seasons of Bell’s vireo in different regions of Illinois (see Fig. 4 for regions). Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Shaded areas show the span of dates during which egg-laying has been recorded. Nesting Habitats and Populations Of the two shrub vireos in Illinois, Bell's is to prairie, or at least to open fields, as the white-eye is to forest. With deforestation, Bell's invades the open forest soil areas, but never the forest, whereas white-eyes are sometimes found in modest numbers in forest. Bell's vireos occupy both upland and bottomland shrub areas (Cunningham 1943), except for upland in the Shawnee Hills, where white-eyes are so numerous. In general, the higher densities of Bell’s vireo popu- lations have been in prairie areas (Ridgway 1871; Du Mont 1947; Hopkins 1974; Linkletter 1975), but a shrub area on cutover forest in the forest-prairie ecotone (Vestal 1960) of western Sangamon County produced the highest densities on record (Robertson 1941, 1944; Table 3). However, forest succession there greatly re- duced the population in just a few years (Robertson & Snyder 1948). Perhaps because its habitat is so transi- tory, Bell’s populations are generally of moderate to low densities (Table 3). On abandoned farm land in Piatt County, Bell's vireos first appeared 28 years after cultivation ceased. The population peaked in the next 2-3 years, then disappeared after 10 years (Kendeigh 1982). On abandoned strip mine land in the south, Bell's was not found until 10-13 years after the cessation of stripping and disappeared after no more than 7 years (Brewer 1958). Bell’s vireos utilized shrub growth along the channelized Kaskaskia River (Kleen 1976-1977), and they are often found in linear shrub growth along coun- try roads, though not usually along busy highways. Bell’s is somewhat more tolerant of people than is the white-eye (Silloway 1894a; Ruegnitz 1952); neither spe- cies is likely to have sustaining populations in urban areas. In the past, orchards provided habitat for Bell’s (Hess 1910), but modern orchards probably do not. August 1985 GRABER, GRABER, & KIRK: Fig. 8.—General] distribution of Bell's vireo. The historical data on Bell’s vireo numbers do not show a consistent trend of gain or loss. The species was not detected in the 1907-1909 cross-country censuses, but was found in 1957-1958 (Graber & Graber 1963). The population may have increased at least on the east edge of the range (Nolan 1958), but in the Rock Island area older counts tended to be higher than more recent ones (Wilson 1906; Schafer 1923; Hodges 1953, 1954). The extensive loss of shrub habitat in recent decades (Smith & Du Mont 1944b; Graber & Graber 1976) im- plies a decline in Bell's population. The question is com- plicated because of the transient nature of the habitat. Plant species used as nest sites by Bell’s vireos in Illinois are common edge species (Table 4). Bellrose (1936), Cunningham (1943), Du Mont (1947), and Eifert (1949) all referred to Bell's vireo nesting in willows, but it is uncertain whether all references were to nest sites or to habitat in general. Heights of 58 Bell’s vireo nests ranged from | to 4 feet (0.3-1.2 m), with a mean of 2.47 feet (0.75 m)—virtually the same as nest heights of the white-eye. A reference to nests as high as 20 and 40 feet (Ballow 1878) is likely a misprint or otherwise in error. The only data on territory size of Bell's vireo is that of Hensley (1950) in east-central Illinois, where a pair occupied 3.1 acres of grass and shrubs, and an unmated male 2.7 acres in the same habitat. Nolan (1960) ob- served similarly large territories in Indiana. ILLINOIS BIRDS: ViIREOS 1] Bell’s Vireo ® cai 48501 feat p 3 a wl feed Bf = TEEe Coheed 5S Po ciaee amy Me | “le | —t- x ror NESTS OR YOUNG = 1950- - ee A= 1900-1949 aS Aen oe @= Before 1900 ek Sea JUNE RECORDS Op-B a o= 1950- et = 1900-1949 — O= Before 1900 Fig. 9.—Breeding records of Bell's vireo in Illinois Nesting Cycle Information on the nesting cycle of Bell's vireo in Illinois comes especially from the studies of Silloway (1894a), Du Bois (1940), Pitelka & Koestner (1942), and Hensley (1950), all of whom worked in central Illinois. Silloway described the song as a short, emphatic warble uttered nervously and with increasing force and rapidity to the end. His phonetics for it: “Quit, oh quit, now quit, why can’t you hear."’ The song has a harsh, irritated quality and oftens ends with a definite ascend- ing or descending note or phrase. Silloway (1913) also noted that the song is delivered in two keys: (1) higher and clearer—more distinctly articulated—and (2) much lower and harsher, the notes seeming to come from closed mandibles. Du Bois (1940) mentioned a song 12 ILLINOIS NATURAL HISTORY SURVEY BIOLOGICAL NOTES No. 124 { Taste 3.—Breeding populations of Bell’s vireo in various Illinois habitats. Birds per County or Hectares Type of Habitat 40.5 ha Years Region Censused Census Reference Woods (unspecified) 0-10 1914-1925 Rock Island (N) 8 J.J. Schafer unpub- (avg 2.0) lished notes Cutover upland oak-hickory forest 1461 1941-1942 Sangamon (C) 20 Map Robertson 1941, 1942, (avg 44.4) 1944, 1948 1944; Robertson & Snyder 1948 Disturbed mixed prairie 5-20 1975-1977 Grundy (N) 16 Map Linkletter 1975, 1977; (shrubs in grassland) (avg 15.2) Linkletter & Wooley 1978 Abandoned farmland 0-10 1946-1958" Piatt (C) 18-24 Map Kendeigh 1982 (shrub and forest edge) (avg 5.4) (13 years) Shrub 0-3 1957-1958 Central 20° Stip — Graber & Graber 1963 (avg 2.0) Pastures 0-2 1957-1958 Central 70 Suip Graber & Graber 1963 (avg 0.6) Early shrub 18 1966 Vermilion (C) 2) Map Karr 1968 Maintained invaded grassland 8.8 1974 Willow Slough, 9 Map Hopkins 1974 Indiana Shrubby field and forest edge 6 1949 Richland (S) +24 Map Sune 1949 Swamp and thicket 7 1950 Jackson (S) 5 Map Brewer & Hardy 1950 Shrub at 1957-1958 Central 52, Suip Graber & Graber 1963 (avg 3.9) “Bell's vireo present only to 1958; the censuses continued to 1971. be, 2 Strip censuses Calculated as cumulative hectares. pattern in which the phrases were alternately interroga- tive and exclamatory and another song characterized by loud squeaks. The male often sings near, and even on, the nest. Pitelka & Koestner (1942) observed a male sing TaBLe 4.—Plants recorded as nest sites of Bell's vireos in (mainly northern and central) Illinois. The scientific name is not included if lacking in the original source. Species Number of Plants Blackberry and raspberry (Rubus spp.) ll Cherry and plum (Prunus spp.) 8 Hazel (Corylus americana) 8 Dogwoods (Cornus racemosa, C. stolonifera) 6 Box elder (Acer negundo) 6 Crab apple (Malus sp.) a Hawthorn (Crataegus spp.) 2 Currant 2 Elm 2 Honeysuckle 2 Red cedar 1 Willow (Salix sp.) ] Witch hazel 1 Osage orange (Maclura pomifera) 1 Multiflora rose (Rosa multiflora) 1 Shingle oak (Quercus imbricaria) ] Hackberry l Red maple (Acer rubrum) 1 Autumn olive (Elaeagnus umbellata) 1 Total 59 98 times between 0622 and 0750 on 2 July. They also saw a female sing at one nest. Scold notes of Bell’s have been described as a series of single notes, ‘‘chick, chick, chick... .” (not high in pitch, uttered by the female at the nest and a rapid “chee, chee, chee... .’’ or a somewhat wrenlike “‘chur, chur, chur... . ’’ uttered by adults carrying food to young (Du Bois 1940). While white-eye nests are often near the center of shrubbery, those of Bell’s vireo are more often on the outer edge, but well concealed from above. They are usually made of grayish weed, bark shreds and fibers, and dried leaves, held with gossamer and lined with fine grasses (Silloway 1894a; Crone 1896; Du Bois 1940). Bell’s nests are drab looking by comparison with white- eye nests. Two Bell’s nests measured by Du Bois were 1.75 inches (4.44 cm) each for the inside diameter at the rim, inside depth was 1.62 and 1.87 inches (4.11 and 4.75 cm), outside diameter was 2.50 inches (6.35 cm) each, and outside depth was 2.50 and 2.75 inches (6.35 and 6.98 cm.) Both adults have been observed to participate in nest building (Hensley 1950). At one nest the female made nine trips and the male six in 70 minutes. At localities in northern, central, and southern Illinois, we observed unmated male Bell’s vireos start nests which they did ‘not (could not?) carry beyond the stage of a thin-walled, fragmentary structure—a mere outline of a real nest. Hensley (1950) noted that the female (alone) finished the interior of the nest. Pitelka & Koestner (1942) and Hensley (1950) found that nest construction required 445 days. Egg laying began on the first day after nest comple- tion at one nest (Hensley 1950) and on the second day after completion at another (Pitelka & Koestner 1942). The eggs are white and finely speckled with cinnamon or reddish brown (Fig. 10). In a sample of 32 May-July nests of Bell’s vireos spaced fairly evenly (historically) from 1881 to 1981, 26 had clutches of four eggs and 6 had three eggs each. All were nests apparently un- molested by cowbirds. In 40 years Harold Holland examined more than 100 Bell’s vireo nests, none of which held more than four (vireo) eggs (Bent 1950). Holland (1923) also found two nests that contained both cowbird and red-winged blackbird eggs, the latter species, of course, a spurious parasite. Cowbird parasit- ‘ism is probably a serious problem for Bell’s vireo. At least four of five nests studied by Pitelka & Koestner (1942) were parasiuzed. In a sample of seven nests stu- died by Silloway (1894a) none was parasitized, and another early student (Crone 1896) had similar expe- rience. In a sample of 12 more recent (1968-1981) north- ern and central Illinois nests, 4 were parasitized by cow- ‘birds. Larger samples are needed to discover whether the problem is growing. Pitelka & Koestner (1942) reported that intervals between the laying of the last egg in failed nests and the laying of the first egg in new nests were 6, 6, and 5 days on different occasions. One female laid 12 eggs in 26 days. At one nest, incubation began with the first egg (Pitelka & Koestner 1942), at another with the second egg (Hensley 1950). Both adults participate in incuba- tion. Hensley observed incubation for 3 hours and 26 minutes, during which the male was on the nest | hour and 29 minutes and the female, | hour and 55 minutes. The average attentive period was 17.8 minutes for the /male and 23 minutes for the female. The male stayed away from the nest as long as 47 minutes, the female no | more than 25. Eggs were not left exposed except for the The incuba- Fa seconds required for the changeover. tion period was 14 days from the laying of the second a Pitelka & Koestner 1942; Hensley 1950). Both adults also brooded and fed the young. During /2.5 hours in the middle of the day when the (three) jnestlings were 3 days old, Hensley obse ‘rved that they | were fed, on average, 9.2 times per hour. The male brought food 14 times and brooded 25 minutes in four sessions. The female brought food 11 times and brooded 51 minutes in two sessions. At a nest with (two) nest- lings 5.5 days old, Du Bois (1940) saw the female feed seven to eight times between 0650 and 0834. The food of b the young nestlings at both nests was almost entirely small naked Lepidoptera larvae. The newly hatched young are naked and pinkish o1 breddish, and the mouth cavity is yellowish without ! : Graser, Graber, & KIRK: ILLINOIS BIRDS: ViREOS 13 Fig. 10O—Nest and eggs of Bell's vireo, 14 June 1984, at Rend Lake markings (Du Bois 1940). At 5 days they were sull essen- tially naked and their eyes were still closed, but they were much larger. Dark feather tracts were showing in the midline of the anterior part of the back, on the edge of the wing, and on the crown and caudal tracts, and white feather tracts were visible on the underparts. At one nest, a young bird stayed 11 days (Pitelka & Koestner 1942), and at another, 12 (Hensley 1950). Hens- ley found the young 30 feet from the nest the day after fledging and 300 feet away 5 days alter fledging. They were being fed by the female. The young uttered a soft, single-noted chip by which the adult located them. Data on nesting success and productivity, and an- nual variation therein, are much needed for adequate samples of Bell's vireo nests (as well as other species) from the three regions of Illinois. A sample of 15 nests (1968-1981) with fairly complete histories from northern and central Illinois had success rates of 31.8 percent for nests and 23.0 percent for eggs, and produced (to fledg- ing), cessful nest). These rates are much below those observed by Nolan (1960) in Indiana unknown on any quantitative basis. One of the 15 nests on average, only 0.9 young per nest (2.6 per suc- Causes of nest failure are mentioned above was torn apart, apparently by a mam- mal, and farm machinery destroyed another. Most (78 14 ILLINOIS NATURAL HisTORY SURVEY BIOLOGICAL NOTES percent) failed in the incubation or laying stage. Cow- birds may have accounted for many of these, as Bell’s vireos tend to desert parasitized nests (Friedmann 1963), especially following the removal of an egg by the cow- bird (Pitelka & Koestner 1942). None of the 15 fledged a cowbird. Du Bois (1940) reported on a nest in which the young were killed by a heavy infestation of mites, and Pitelka & Koestner (1942) reported one young lost to an infestation of fowl mites (Liponipsus syluiarum). Bell’s vireos sometimes apparently attempt to rear more than one brood per year, as indicated by a study of banded birds in Indiana (Nolan 1960), but the incidence of such behavior and its effect on a population remain to be determined. Fall A Bell’s vireo (adult?) was in molt in Richland County as early as 2 July (USNM 114864), and some birds in northern and central Illinois appeared to be in fresh plumage by 28-29 August. As with many species, the fall departure of Bell’s is not a conspicuous event (Fig. 7). We saw only 1.0 Bell’s in fall to 2.2 in spring in northern Illinois, and 1.0 to 1.6 in the central region. Most of the birds detected were singing. We did not detect the species in our fall census transects. Bell’s vireos have been found singing on terri- tories as late as 7 September in northern I]linois (Mum- ford 1959a) and 5 September in central Illinois (Pitelka & Koestner 1942). In central Illinois, highest counts (five to six birds) came 18 August-8 September. Bell’s vireo has not been recorded as a television tower casualty in Illinois, and nothing is known of the actual migration flights. The latest fall records of Bell’s in Illinois were 2 October in the north (Ford 1956), 23 September in the central region (Kleen 1982), and 22 September in the south (Widmann 1907). A figure in Anderson & Bauer (1968) seems to indicate an early October record for the St. Louis area, but the precise date was not stated. A Bell’s vireo at Barrington, Illinois, on 14 November (Fawks 1965) was very late—possibly an accidental record. Specimen Data Illinois specimens of Bell’s vireos have been referred to Vireo b. bella (Ridgway 1904; Brodkorb 1930). Weights of Indiana specimens of both adult and immature Bell’s vireos were presented by Nolan (1960). SOLITARY VIREO (Vireo solitarius) (Fig. 11) Spring Migration The earliest reports of solitary vireos in Illinois were 15 and 21 April in the south (Fig. 12; Cooke 1909); 18, 20, and 21 April in the central region (Hunt unpub- lished 1976; Bohlen unpublished 1979; Kleen 1974b); and 11] and 18 April in the north (Fig. 12; Chase 1899). Peak numbers have been seen 21 April—13 May in the © south (3—5 per day) and 2-18 May in the central region (4-11 per day). In the north only 1-2 solitary vireos have been reported per day in spring (Fig. 12)—numbers that do not realistically reflect the population there. How- No. 124 » ever, the highest single county count of the solitary dur- — ing 10 years (1972-1981) of the Audubon Spring Bird Count was 21 birds—on 6 May—in McHenry County, where the number of observers was 14, i.e., fewer than 2 — birds per observer (Kleen 1981b). At Davenport, P.C. Petersen banded 14 solitary vireos on 10 May, and we would expect field counts to be higher in northern IIli- nois than present data show. Probable transient solitary vireos have been seen as late as 8 June in northern Illinois (Ferry 1908) and 19 May in the south (George 1968). The record of a male solitary in Marshall County on 6, 23, and 24 June (Kleen 1982-1983) is enigmatic—extremely late for a transient, but with no certainty of breeding in the area. However, the locality is not far from the one known breeding area in the state (see below). Cooke (1884a, 1888) found that the migration of the solitary vireo in the Mississippi Valley was relatively fast compared with those of other species there. Both Bohlen (1978) in Illinois and Dinsmore et al. (1984) in Iowa felt that solitary vireos preferred upland and edge habitats. However, the highest spring densi- ties In our censuses were in bottomland forest, both in central and southern Illinois (Table 5), leading us to suspect that transients have no particular habitat pref- erence but concentrate where the food 1s. Solitary vireos regularly sing during both their spring and fall sojourns in Illinois (Ridgway 1889, 1915a; Lewis 1923). Ridgway (1889) described the song, which sounds somewhat like a soft, hesitant yellow- throated vireo song. The regular breeding range of the solitary vireo lies north of Illinois (Fig. 13). Bjorklund 1979-1980, 1980— 1981) has presented data on the nesting of the solitary vireo in Illinois. Despite references to the breeding or summering of this species in northern Illinois (Roberts 1923; George 1971; American Ornithologist’s Union 1983), the latter of which may refer to Bjorklund (1979- 1980), the only certain nestings in the state have been at Sand Ridge State Forest (Mason County) in mixed pine plantation-hardwood forest habitat (Bjorklund 1979- 1980, 1980-1981). There a nest 10 feet (3.0 m) high ina 45-foot (13.7 m) white pine (Pinus strobus) was found on 16 May 1979. On 3 June the nest contained one vireo egg that never developed and a nestling cowbird that survived to at least 9 June. The cowbird was gone—as were the vireos—on 13 June. The following year a pair of solitary vireos was present in the same area in May and a completed nest was found on 14 June within 50 feet (15.2 m) of the 1979 nest site. Subsequently, that nesting failed. As Bjorklund (1980-1981) pointed out, this second nesting attempt seems to represent a clear example of homing by one or both vireos, as the species es ' ‘August 1985 ; Fig }was not known to occur anywhere else in the state in ssummer, and possibly no closer than the Indiana Dunes } (Fawks 1968b)—about 170 miles (274 km) away. Fall Migration | The earliest indication of the fall migration in [h- jnois was Gault’s (1901b) record of a solitary vireo at Glen Ellyn on 11 August. This record is exceptionally early, as the earliest other fall records for the north were not until 3 and 4 September (Schafer 1923; Clark & Nice 11950). Early fall records for the central region were: 29 )August and | September (Bohlen unpublished 1977; /Kleen 1980a) and for the south, 26 August and 8 Sep- } tember (George 1968; Wilhelm 1954). The earliest tower- }killed specimens were found 20 September in central Illinois and 28 September in the south. High counts in ;the north were three and nine per day on 7 and 29 September (Fig. 12). At Davenport, P.C. Petersen banded 13 solitary vireos on 20 September 1977 (Dinsmore et al 11984) and a total of 38 between 24 August and 12 October 1977—considered to be above-average numbers (Halmi 1977). By comparison, our fall (1968) count was only 15 solitaries. In the central region, peak numbers } (6-12 per day) were seen 26 September—10 October. In ) the south again, the counts were low, the highest only )three per day, on 5 and 16 October (Fig. 12). Higher } numbers will surely be found in late September as well GRABER, GRABER, & KIRK: 11.—Solitary vireo at its nest at Sand Ridge State Forest, Mason County ILLINOIS BIRDS: VIREOS 15 Photo by Dr Richard Bjorklund as in October. Much of the migration probably occurs regularly in October (Fig. 12), November records (Sanborn 1922; Hagans & Shaw 1961; Fawks 1967; Kleen & Bush 1972; Kleen 1975a, 1976b, 1978, 1980b; Bohlen 1978, unpublished 1981 and 1982) —to 26-27 November (Fawks 1967; Kleen 1980a)—that it seems certain that some migration in November is and there are so many normal for the solitary vireo The ratio of our counts—spring to fall—was 1.0 to 7 in the north, 1.0 to 3.4 in the central region (1.0 to 3 to 1.0 in the fall ratio in the ) 2.6 in the census transects), and | south The south appears to be typical of many Illinois species, 1983). At Daven port, P.C. Petersen's banding study showed more soli (1.0 to 1.0 in the transects) low including most warblers (Graber et al tary vireos to be present in fall than in spring, but at Chicago, Dreuth saw the species with greater frequency in spring than in fall (Clark & Nice 1950) Relatively few (19 picked up) solitary vireos have killed at commensuratt been central Illinois television towers probably with a generally low. stat population, as shown by the counts and censuses (Table 5) The habitats with highest densities of solitary vireos in fall were forest edge and shrub in the central region both cases and in pine habitat in the south (Table 5), in differing from those in spring 16 10 BIRDS COUNTED PER DAY 12 24 APR Our only observations on food of the solitary vireo were of individuals eating a very large (3-inch or >75- mm), Lepidoptera larva on 28 September and fruit of Cornus florida on 5 October—also listed by Chapin (1925). MAY 12 24 MAY ILLINOIS NATURAL HistoRY SURVEY BIOLOGICAL NOTES 12 24 JUN ACTIVE NEST (1979) 12 24 JUN 12 24 JUN 12 24 V2 2h 1224 JUL NORTH JUL CENTRAL JUL SOUTH TV KILLS > Ke) No. 124 NOV Fig. 12.—Migration seasons of the solitary vireo in different regions of Illinois (see Fig. 4 for regions). Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Shaded area (central region) shows time of nesting activity. Dash lines show numbers killed at television towers during fall migrauon. Gross weights of specimens killed, 27 September—12 October, were: one adult male (still in molt on back, rump, and breast on 27 September), 18.3 g; two very fat immature males, 16.5 and 16.7 g; and one immature female, 16.5 g. Of six specimens we aged from this sam- ple (two were not weighed), only one was an adult. Taste 5.—Spring and fall population densities of the solitary vireo in Illinois (1979-1981). Season and Habitat Spring (21 April-22 May) Mature bottomland forest Mature bottomland forest Mature upland forest Mature upland forest Forest edge and shrub Forest edge and shrub Loblolly pines Fall (27August—16 October) Mature bottomland forest Mature bottomland forest Mature upland forest Mature upland forest Forest edge and shrub Forest edge and shrub Loblolly pines (1979-1980 only) County or Region Piatt (C) Johnson (S) Piatt (C) Pope (S) Piatt (C) Pope (S) Pope (S) Piatt (C) Johnson (S) Piatt (C) Pope (S) Piatt (C) Pope (S) Pope (S) Number of Censuses Cumulative Hectares Censused Birds per 40.5 ha Maximum Mean 1.2 0.5 ce Leia Bhs \ ‘ Fig. 13.—General distribution of the solitary vireo. YELLOW-THROATED VIREO (Vireo flavifrons) (Fig. 14) Spring Migration The earliest reports of yellow-throated vireos in or near Illinois were 31 March and 8 April in the south (Fig. 15), 28 March and 14 April in the central region (Kleen 1975b; Peterjohn 1981), and 14 and 25 April in the north (Peattie 1938; Smith 1942; Clark & Nice 1950). Peatue’s reference to “‘many”’ yellow-throated vireos at Kennicott’s Grove on 14 April may cast doubt on that record. The yellow-throated is the first of the vireos to arrive in spring (Widmann 1907), but large numbers in the north so early would be unusual. Highest numbers were seen 16 April-8 May in the south (12-26 per day), 7-14 May in the central region (6-7 per day), and 13-22 May in the north (4-10 per day). The migration probably extends into early June, at least in the north (Ferry 1908). The counts of Smith and his students (1903-1925) in east-central Illinois were not notably different from our more recent counts. Spring densities in the south were higher in bottomland than in upland forest and were about three times higher than breeding densities in bottomland (Tables 6 and 7). In central Illinois, densities in spring and June were similar. Graser, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 17 Distribution The yellow-throated vireo probably nests in every county in I}linois, and the absence of records for many counties (Fig. 16) almost certainly implies inadequate exploration. A forest species, the yellow-throated is most numerous in the south (Fig. 15), though it occurs throughout the eastern deciduous forest (Fig. 17). In addition to records plotted (Fig. 16), there are June records for unspecified localities in Kane County (Green- berg 1982), the ‘‘dunes area’ of Chicago (Sanborn 1921), and a nest on the Cook-Lake county line (Ford 1956). Nesting Habitats and Populations The breeding habitat of the yellow-throated vireo seems poorly defined. Primarily a forest interior species (Kendeigh 1982), it also sometimes nests in forest edge and in bottomland (Ridgway 1874; Gates 1911) as well as upland (Barnes 1890; Cahn & Hyde 1929)—not con- spicuously favoring one over another (Table 7). It is unlikely that human residential areas could provide even marginal habitat for this species. Characteristics of vegetation, which we measured (Graber et al. 1977) in 18 forest study areas in southern and central Illinois, showed no consistent relationship to yellow-throated vireo populations. However, the higher populations in bottomland forest were in stands with relatively high densities (50+ per acre or 123+ per ha) of trees over 10 inches (25.4 cm) DBH (r = 0.538, n = 10, p > 0.05 < 0.10) and high densities (7+ per acre or 17+ per ha) of trees in the 14- to 16-inch (36- to 41-cm) DBH class (r = 0.772, n= 10, p < 0.005). The relationship did not hold for upland stands, and the data may simply imply that yellow-throated vireos favor forest with relatively high numbers of moderately large trees. Nests we have seen have generally been in fairly large (> 10 inches or 25.4 cm DBH) trees. Few data are available on nest sites—or other habitat features—in I]linois. Of 11 nest sites known to us in southern and central Illinois, 4 were in shagbark hicko- ries (Carya ovata), 3 in oaks (Quercus rubra, Q. alba), and 2 in maples (at least one Acer saccharum), plus | each in a sweet gum (Liquidambar styraciflua) and an “ash.”’ The nests were generally high (15-50 feet or 5—15 m), with a mean of 30.5 feet (9.3 m). Four territories of yellow-throated vireos measured in upland forest in east-central Illinois by Allison (1947) ranged from 2.4 to 3.3 acres (0.7-—1.0 ha), with a mean of 2.8 acres (0.8 ha). The yellow-throated vireo is usually a low-density species in Illinois, averaging under 10 birds per 40.5 ha, often only | or 2 per 40 ha for large census areas (Table 7). There is no evidence that the species’ status has changed greatly within historical times. The yellow- throated vireo was not detected on the first cross-country censuses in Illinois, probably because of the small amount of forest censused in 1906-1909 (Graber & Graber 1963). Notably high populations have been reported in northern I}linois in some years (Boulton & 18 ILLINOIS NATURAL HISTORY SURVEY BIOLOGICAL NOTES Fig. 14.—Yellow-throated vireo working on its nest in Jefferson County, May 1982. Photo by Bowie Hannah. Pitelka 1938a; Mumford 1959b), but numerical values cannot be assigned to these observations. Even more than for most Illinois species, data on the breeding biology of the yellow-throated vireo are mea- ger, probably because of the (high) location of nests. No Illinois data exist on such fundamentals as time require- ments for any phase of the nesting cycle, nestung suc- cess, productivity, or the number of broods attempted. We have heard two distinctly different songs from yellow-throated vireos in I]linois: (1) the most common, a leisurely delivered, vibrant series of phrases (three o1 more)—‘‘shree-ur, shree-ur, shree-ee,’’—and (2) a vocal- ization that sounds like a song but which may have an entirely different function than the common song. Our phonetics are: “‘perteee, terteee, pee-yurr,”’ the “‘teee”’ notes rising and the last note falling. A call that is prob- ably an alarm call is an accelerating series of harsh “cha-cha-cha”’ notes, similar to a call uttered by the solitary vireo. At least one of a pair of yellow-throateds, looking for a nest site, called “‘pink-pink-pink”’ almost continually as they went from tree to tree. Yellow-throated vireos have been seen building nests between 23 April and 19 June in southern Illinois, where the span of dates for egg-laying was 10 May—15 July. Egg dates in the north were | June—20 July (Fig. 15). The eggs are creamy white and speckled about the large end with reddish brown (Reed 1965). Five Illinois nests of unknown histories, but not parasitized by cow- birds, had clutches of four eggs (two nests, central and © south) and three eggs each (three nests, north and cen- tral). In addition, a Vermilion County nest had four eggs, plus one cowbird egg just ready to hatch, on 1] June (S.D. Bailey unpublished 1981). In the south, yellow-throateds were feeding a fledgling cowbird on 16 June and a stub-tailed vireo on 12 August. Friedmann — (1963) noted that this species is a frequent victim of the cow bird. The longevity of a yellow-throated vireo banded and recovered in northeastern Illinois was 5 years and 1] months (Kennard 1975). As the bird was an ‘adult’ (AHY) when banded in June 1968, it was at least several months older than the age indicated. We have noted that yellow-throated vireos seen after 20 August in central and southern Illinois appear to be in fresh plumage. Gault (unpublished 1897), on the No. 124) other hand, observed one in northern Illinois that was | in heavy molt on 22 August. Adult males killed on 17 and 27 September at central Illinois television towers were sull in molt, and an immature killed on | October Was In extensive molt. Fall Migration As is typical of southern-ranging species, fall counts - of yellow-throated vireos tend to be low (Fig. 15, Table 6). We saw 1.6 1n spring to 1.0 in fall in the north, 1.4 to 1.0 in the central region (1.6 to 1.0 in the census tran- sects), and 7.0 to 1.0 in the south (2.4 to 1.0 in the transects). Dreuth (Clark & Nice 1950) at Chicago saw yellow-throated vireos an equal number of times (14) in spring and fall. Of nine birds aged from the tower kills, five were adults and four were immature. We saw at least twice as many yellow-throated vireos on the western side of the state as on the east in both central and southern Illinois in both spring and fall. As is also typical of the more southern-ranging spe- cies, yellow-throated vireos are not represented in televi- sion tower kills in large numbers—43 (known to us) have been picked up in fall from 1957 through 1979, mainly in central Illinois. The moderate numbers also reflect the fact that the total population of yellow- throateds is not very large. Kills of this species appear to come late (late September—early October) by compari- son with the field counts (peak numbers in early Sep- tember, Fig. 15). These results are partly a matter of most towers being examined late in the season (Graber et al. 1983) but may also mean that we missed the later migrants, and or that kill-inducing weather is more prevalent later. BIRDS COUNTED PER DAY ui JUN dle «EGG DATES, JUN NORTH EGG DATES , CENTRAL Graber, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 19 12 24 JUL AUG SEP OCT Ve TV KILLS 12 24 JUL AUG SOUTH EGG LAYING (SPAN OF DATES) 12 24 MAY Fig. 15.—Egg-laying and migration seasons of the yellow-throated vireo in different regions of Illinois (see Fig. 4 for regions). Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Shaded areas show the span of dates during which eggs or laying have been reported. Dash lines show numbers killed at television towers during fall 12 24 JUN 17: 24 APR JUL AUG migration. A bird killed at a Springfield TV tower on 26 August implies that the migration had started by that date. One seen at Charleston on 16 November (Kleen 1975a) was exceptionally late by comparison with other “‘last-seen”’ records, i.e., mid-October in the north (Woodruff 1907), 16 and 17 October in the central region (Kleen 1976a, 1982), and 15 October in the south (Ridgway 1874). Food In typical vireo fashion, the yellow-throateds feed heavily on Lepidoptera, but take more hemipterans than most vireos and less vegetable food (Chapin 1925). In stomachs of three Illinois specimens Forbes (1878) found three Lepidoptera (one adult, two larvae), two beetles, and a fly. In our miscellaneous notes are two records of yellow-throated vireos eating adult Catocala moths after having removed the wings and one record of a bird eating a hairy caterpillar. Frank Smith (un- published 1919) saw a bird of this species eat a butterfly (Vanessa?). 20 ILLINOIS NATURAL History SURVEY BIOLOGICAL NOTES No. 124 Taste 6.—Spring and fall population densities of the yellow-throated vireo in Illinois (1979-1981). County Number Cumulative : = or of Hectares Birds per A03iha Season and Habitat Region Censuses Censused Maximum Mean Spring (9 April-31 May) Mature bottomland forest Piatt (C) 9 186 2.3 0.7 Mature bottomland forest Johnson (S) 20 416 9.5 3.5 Mature upland forest Piatt (C) 13 279 9.2 1.3 Mature upland forest Pope (S) 21 433 3.9 0.9 Forest edge and shrub Piatt (C) 10 203 9.0 ee, Forest edge and shrub Pope (S) 17 337 0 Loblolly pines Pope (S) 10 179 0 Fall (1 August-29 September) Mature bottomland forest Piatt (C) 17 343 6.3 1.4 Mature bottomland forest Johnson (S) 18 379 5.7 1.8 Mature upland forest Piatt (C) 21 409 4.2 0.6 Mature upland forest Pope (S) 15 326 1.9 0.2 Forest edge and shrub Piatt (C) 20 411 4.0 0.3 Forest edge and shrub Pope (S) 17 351 0 Loblolly pines (1979-1980 only) Pope (S) 9 159 0 Tas_e 7.—Breeding populations of the yellow-throated vireo in various Illinois habitats. Birds per County or Hectares Type of Habitat 40.5 ha Years Region Censused Census Reference Forest (all types, including edge) 0-1 1957-1958 Central 87" Sup Graber & Graber 1963 (avg 0.5) Forest (all types, including edge) 2-3 1957-1958 South 138 Suip Graber & Graber 1963 (avg 2.4) Floodplain forest 6 1948 Sangamon (C) 31 Map Snyder et al. 1948 Floodplain forest 0-16" 1949-1951, Piatt (C) 10 Map Kendeigh 1982 (avg 5.6) 1963, 1967 Bottomland forest 0-1.84 1978-1981 Central 193 Suip This paper (avg 0.4) Bottomland forest 0-5.8 1973-1981 South 1,129 Suip This paper (avg 1.1) Upland forest 0+-25.8? 1949-1951, Piatt (C) 13 Map Kendeigh 1982 (avg 10.2) 1962, 1963, 1967 Upland forest 0-2.09 1978-1981 Central 123 Suip This paper (avg 1.0) Upland forest 0-7.6 1974-1981 South 623 Sup This paper (avg 1.2) Oak-maple forest 0-3.4 1927-1976 Champaign (C) 24 Map Kendeigh 1982 (avg 0.8) (44 years) a Strip censuses calculated as cumulative hectares. } ‘Based on data in table of Appendix 3 of reference. Specimen Data Ridgway (1904) noted that yellow-throated vireos from the Mississippi Valley were smaller than those from the Atlantic coast. No races are recognized (Ameri- can Ornithologists’ Union 1957). Gross weights of yellow-throated vireos killed 17 September—1 October were, for two adult males, 18.9 and 19.6 g; for one adult female, 18.4 g; and for three immature females, 17.8, 20.0, and 20.5 g. The heavy immatures were very fat (4 on a scale of 0-5); the rest were only moderately fat (2-3). August 1985 NESTS OR YOUNG @= 1950- sr cam A= 1900-1949 me ah @= Before 1900 a JUNE RECORDS o= 1950- A= 1900-1949 O= Before 1900 Fig. 16.—Breeding records of the yellow-throated vireo in Illinois. WARBLING VIREO (Vireo gilvus) Spring Migration The earliest reports of warbling vireos in Illinois were 6 and 10 April in the south (Cooke 1909; Kleen 1974b), 15 and 16 April in the central region (Cooke 1885; Campbell unpublished 1972; Bohlen unpublished 1977; Fig. 18), and 23 and 26 April in the north (Kleen 1979a, 1981b). At least in central and southern [linots, numbers of warbling vireos differed consistently be- tween the western side (from the Illinois River west) and the eastern side of the state (Fig. 18). Peak numbers have been seen 29 April—18 May in the south (west, 23-35 pet day; east, 8-10 per day), 29 April-26 May in the central region (west, 26-36 per day; east, 6-10 per day), and 11 May-3 June in the north (west, 13-18 per day). Com- parable data are lac king for the northeast, though Graser, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 21 Yellow-throated Vireo BREEDING RECORDS re a es = + 5 1 ry Me, : = | oe i) { te $ 4 oO2 re. *) dg. | “> tea oe PR Me & \ - et go Ba SS X : D Si ft Ons Yellow-thro Vireo ee ere <= POR leas ov No * } >» = a L t Ranges lk [_] BREEDING winter a a tae SSS | [Dem of Geography ~Unew of tenet = ea Fig. 17.—General distribution of the yellow-throated vireo Dreuth apparently did not find large numbers of war- bling vireos at Chicago (Clark & Nice 1950). A special comparative study is needed for the Hlinois and Missis- sippi valleys, but it is our impression that the Illinois had higher numbers of warbling vireos. In east-central Ilinois the counts of warbling vireos by Frank Smith and his students (1903-1925) were sim- ilar to our more recent counts. Highest spring densities were in bottomland forest in the south and in forest edge and shrub in the central region (Table 8). In the south spring densities were about three to four times the June densities (Table 9), but even so, the total number of birds passing through the area would not be large. Distribution Much of the extensive range north and west of [linois—west of the great plains (Fig. 19)—has forms of the warbling vireo that do not occur in Illinois. The Illinois range (Fig. 20) is still incompletely known, but the species probably nests in every township in the state, In addition to records plotted in Fig. 20, there are breed- ing records for unspecified localities in these counties: Putnam (Hess unpublished 1905); Knox and Marshall (H.M. Holland unpublished 1950, 1957); Whiteside (Thompson 1958); and Richland, Adams, Schuyler, and Shelby (Kleen 1977-1978, 1978-1979; Greenberg 1982) Pare, ILLINOIS NATURAL HisTORY SURVEY BIOLOGICAL NOTES 20 2 AL eo 12 24 40 APR MAY JUN WEST BIRDS COUNTED PER DAY 4 APR MAY JUN EAST © 12 24° 12 24 12 24 APR MAY JUN NORTH EGG LAYING (SPAN OF DATES) 12 24 JUL CENTRAL JUL AUG SEP OCT SOUTH eastWo oO, E66 LAYING TV KILL Wee JUL AUG SEP OCT Fig. 18.—Egg-laying and migration seasons of the warbling vireo in different regions of Illinois (see Fig. 4 for regions). Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Shaded areas show the span of dates during which eggs or laying have been recorded. Dash lines show numbers killed at television towers during migration. Nesting Habitats and Populations The warbling vireo is tolerant of humans (Ridgway 1887; Hess 1910; Schantz 1931), and the highest density recorded for the species in Illinois (79 per 40 ha) was in woodland modified by the presence of human housing (Beecher 1942; Table 9). Note, however, that the habitat sample was small, as were those in studies by Fawks (1937, 1938) and Karr (1968). Data from small census plots (under 15 ha) are not comparable with figures for large areas (Table 9). Though warbling vireos breed even in urban residential habitat, the densities are low, as they are generally for this species wherever it occurs (Table 9), at least in recent times. Hess (1910) noted that the warbling vireo did not occupy forest habitat in Champaign County but did in the Illinois Valley (see also Barnes 1890 and Gates 1911). The highest densities No. 124 | August 1985 Graber, GRABER, & KIRK: ILLINOIS BIRDS; VIREOS 23 Taste 8.—Spring population densities of the warbling vireo in Illinois (1979-1981). —eeeeeeeeeeeeeeeeeeee——e—e—e—S—S—S—S—E——EeSSESS—————————————__—_—_____________ County Number Cumulative 2 ~ fa eciaves Birds per 40.5 ha Season Region Censuses Censused Maximum Mean Spring (27 April-18 May) Mature bottomland forest Piatt (C) 3 62 2.3 0.7 Mature bottomland forest Johnson (S) 9 183 9.2 18 Mature upland forest Piatt (C) 7 128 0 Mature upland forest Pope (S) 8 161 1.9 0.2 Forest edge and shrub Piau (C) 5 104 6.0 1.9 Forest edge and shrub Pope (S) 7 138 0 Loblolly pines Pope (S) 4 70 0 i we have recorded (3-11 per 40 ha) were in the Illinois Valley, where the forest is much dissected by streams and lagoons. Ridgway (1874) considered the warbling vireo a bottomland forest species in the Wabash Valley, but even then it was probably confined mainly to the edges or openings, such as those along streams (Ridg- way 1889; Widmann 1907). On the upper Mississippi River, Hodges (1951) found 31-44 pairs of warbling vireos on Credit Island. If the whole 400-acre island be considered as habitat, this number translates to 15-22 birds per 40 ha, a high density for this species on a large area, and points out the possible importance of park- land as habitat. Older references (Barnes 1890; Ridgway 1889; and others) indicated high populations of the warbling vireo in Illinois, but Ridgway (1915b) noted a severe Taste 9.—Breeding populations of the warbling vireo in various Illinois habitats. Birds per Habitat 40.5 ha Years Urban residential 1 1958 ‘Urban residential 9 1958 Urban residential p+? 1976-1977 Modified woodland 79.5 1937 Forest (all types, including edge) 0-1 1957-1958 (avg 0.5) Forest (all types, including edge) 03 1907, 1909 (avg 1.7) Floodplain forest 6 1948 Floodplain forest 52 1966 Bottomland forest 0-11.2 1978-1981 (avg 1.5) Bottomland forest 0-2.5 1973-1981 (avg 0.5) 13.3-26.7 (avg 20.0) Second growth hardwood 1937-1938 Cutover upland oak-hickory forest 0-41.1 1941-1942 (avg 1.0) 1944, 1948 Shrub, including edge shrub 044 1957-1958 (avg 2.3) Late shrub 24 1966 Orchard grass, tall fescue meadow“ + 1980 Strip census calculated as cumulative hectares. + = less than one bird per 40.5 ha. This meadow had a small stream with two large oaks County or Hectares Type of Region Censused Census Reference North 65" Sup Graber & Graber 1963 South 40 Suip Graber & Graber 1963 South 139 Strip This paper Lake (N) 1 Nest Beecher 1942 Central 87 Surip Graber & Graber 1963 South 24 Suip Graber & Graber 1963 Sangamon (C) 31 Map Snyder et al. 1948 Vermilion (C) 6 Map Karr 1968 Central 193 Suip This paper South 1,129 Suip This paper Rock Island (N) 6 Map Fawks 1937, 1938 Sangamon (C) 20 Map Robertson 1941, 1942, 1944; Robertson & Snyder 1948 South 52 Suip Graber & Graber 1963 Vermilion (C) 9 Map Karr 1968 McLean (C) 12 Map Birkenholz 1980 at one end of it and woodland nearby 24 i ‘| fire cre i cl 1 en’) , Pen ~ 4 | = A wie a" #) ZY | ” rs J. roe . Vi ( \ © re ~ 9 0 Warbling Vireo ~ 3 he Ny oe ne ee &. ees Aa, L [7] areeoine a aye sie [+ Bl im 4 5 = WINTER SY LL : ( ° roo 400 600 so. J aa a na Dept of Geography - Univ of Ilhinore 110% soo Ca Lie > j70* Fig. 19.—General distribution of the warbling vireo. drop in the population. The only comparative data available are from the cross-country censuses for forest in the southern and central regions of the state. Dens1- ues for the habitat in 1907-1909 were: south, 1.7 birds per 40 ha; central, 0; and for 1957-1958: south, 0; and central, 0.5 bird per 40 ha. The figures do not indicate a major change in numbers of warbling vireos, though possibly some loss in the south since 1909. Plant species that have been particularly associated with the warbling vireo were large silver maples (Ridg- way 1889), maples in town and apples on farms (Hess 1910), and cottonwoods and willows (Swink 1976). Of 44 plants identified as nest sites of warbling vireos, mainly in northern and central Illinois, 11 were maples (9 soft or silver, | sugar, 1 box elder), 8 cottonwoods (plus | unspecified poplar), 5 oaks (3 white), 5 hackber- ries, 3 apples, 3 willows, 2 sycamores, and 1 each of birch, cherry, American elm, hickory, pear, and walnut. The most commonly used trees are primarily bottom- land species. In the Illinois Valley, where warbling vireos were generally most numerous, one tree species— silver maple (Acer saccharinum)—was the overwhelm- ing dominant. The presence of fruit trees in the list suggests that orchards have provided habitat for the warbling vireo, but the transect censuses revealed none in the orchard habitats sampled (Graber & Graber 1963). Nest heights ranged from 5 to 60 feet (1.5-18.3 m), with a mean of 26.6 feet (8.1 m, 2 = 34) and modes at ILLINOIS NATURAL HistORY SURVEY BIOLOGICAL NOTES No. 124 Warbling Vireo BREEDING RECORDS Mirman. oF 1 es ian laie NESTS OR YOUNG @ = 1950- A= 1900-1949 @= Before 1900 JUNE RECORDS o = 1950- A= 1900-1949 O= Before 1900 Fig. 20.—Breeding records of the warbling vireo in Illinois. 20-25 feet (6-8 m) and 3540 feet (11-12 m). On strip-mined land Brewer (1958) found warbling vireos in nearly all of the recovery stages, including young growth (10-15 years). There are no Illinois data on territory size of the warbling vireo, and probably because of the difficulty of reaching most nests, there are essentially no data on the nesting cycle. Widmann (1907) said that at St. Louis the warbling vireo’s song could be heard from April to 20 September with a brief pause in August. Even more than the other species, this vireo 1s well known for its song, its persist- ence In singing, its singing at the nest (Elliott 1901; Schantz 1931), and even for its singing at night (Eifrig 1915). Farwell (1919) described the song as a lovely smooth flowing warble, meandering in rhythm, unlike the energetic notes of the red-eye. A commonly heard ' : ) : August 1985 call note—‘“‘frit’” or “‘frut’’—sounds something like a call of the ruby-crowned kinglet. Warbling vireos also scold a lot—a harsh sustained yammering—in the vicin- ity of their nests. Cooke & Widmann (1884) noted mating in this spe- cies by 29 April at St. Louis. Data on the nest, its struc- ture, and the time required for building are lacking fon Illinois populations, though Cooke (1884b) described an aberrant nest of this species. A nest in extreme north- ern Illinois was complete by | May (McKinney 1966). The nest is much like those of other vireos (Fig. 21). The egg-laying season extends from at least 20 May to 15 July in northern Illinois (Fig. 18). Data for the other regions are more fragmentary. In a May—July sample of 19 nests—mainly from northern and central Illinois—clutches were: five eggs, 1; four eggs, 14; three eggs, 4 (mean clutch, 3.8 eggs). None contained cowbird eggs. Parasitism of warbling vireo nests has been re- ported in Illinois by Friedmann (1963), who considered the species to be a frequent host of the cowbird. Poling (1889) stated that in a “large number” of warbling vireo sets from the Quincy area, three had cowbird eggs— presumably a much lower parasitism rate than in the red-eyed vireo (also see under red-eyed vireo). Data on nesting success and productivity are lacking for all populations and habitats of the warbling vireo. Preda- uion on a warbling vireo nest by a bull snake was “— 7 ® —" Graser, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 25 reported by Cooke (1884b) We have seen warbling vireos that appeared to be in fresh plumage as early as 1] August in central Illinois. Fall Migration The onset of the fall migration of warbling vireos is difficult to discern because of the presence of local breeders. In the south, Nelson (1877) saw no warbling vireos until 27 August, after which they became com- mon. The statement could refer to an influx of migrants, or merely to the resurgence of song (i.e., increased con- spicuousness) in the local breeding population. Our counts in central and northern Illinois show a similar pattern—a striking increase in late August (Fig. 18)— and are subject to the same interpretations. A warbling vireo killed at a central Illinois television tower on 2 September indicates active migrauion by at least that date. Peak numbers of warbling vireos were seen 25 August—28 September in central Illinois (6-17 per day) and 18 August—5 September in the north (6-18 per day, Fig. 18). For reasons unknown, few warbling vireos have been detected in southern Illinois in fall (Fig. 18). Nelson's (1877) reference to their being common at Mt. Carmel in the fall of 1875 cannot be interpreted numeri- cally. Bs ite eae Fig. 21.—The nest of a warbling vireo 7.5 m high in an American elm (U'lmus americana), Photo taken 14 June 1984 at Rend Lake. Note the juvenile (on the edge of the nest) just ready to fledge 26 ILLINOIS NATURAL HistoRY SURVEY BIOLOGICAL NOTES In northwestern Illinois, Schafer (1917-1918) last saw presumed locally breeding warbling vireos between 5 and 14 September. The latest records were 14 and 15 October in the north (Boulton & Beecher 1939; Clark & Nice 1950), where October records are very few; 15 October in the central region (Bohlen 1978), where the latest television tower kill of this species was 6 October; and 27 and 30 September in the south (Cooke 1909; Kleen 198la), where the latest tower kills were 21 and 22 September. Warbling vireos appear to be rare as casual- ties at Illinois television towers (Fig. 18). The ratio of counts—spring to fall—was 2.4 to 1.0 in northern Illinois and 4.8 to 1.0 in the central region (none was seen in the fall census transects). In both Dreuth’s counts at Chicago (Clark & Nice 1950), and Petersen’s banding record at Davenport, Iowa (Dins- more et al. 1984), the ratios strongly favored spring also. Whether warbling vireos are just very difficult to detect in fall, or are absent for the most part, remains to be determined. Food When Forbes (1883) examined three spring speci- mens of warbling vireos from an area with cankerworm (Lepidoptera) infestation, he found the stomach con- tents to be 44 percent cankerworms, 35 percent other caterpillars, and 15 percent Coleoptera, of which about one-third were larvae of Carabidae. In general, war- bling vireos feed heavily on Lepidoptera (Chapin 1925). In fall, especially, they also take wild fruit, e.g., elder- berries (Ridgway 1915a) and pokeberries, though Chap- in’s study indicates that vegetable food is taken in small quantities compared with that consumed by the red-eye. Holcombe & Yeomans (1938) observed a warbling vireo feed on larvae extracted from oak leaf blisters. Only the nominate race (V. g. gilvus) has been recorded, or is to be expected, in Illinois (Ridgway 1904). PHILADELPHIA VIREO (Vireo philadelphicus) Spring Migration The earliest reports of the Philadelphia vireo in IIli- nois were 20 April in the south (Ridgway 1874, 1889), 27 April in the central region (M. Campbell unpublished 1983), and 3-4 May in the north (Fig. 22; Ford 1956). Peak numbers have been seen 5-12 May in the south (2-3 per day), 13-24 May in the central region (4—9 per day), and 10 May-—1 June in the north (3-8 per day) (Fig. 22). Nelson (see Cory 1909) referred to 12 specimens per hour at Waukegan about 20 May. The latest spring records were 4 and 8 June in central and northern IIli- nois (H.D. Bohlen unpublished 1976; Ford 1956) but strangely early—22 May—in the south, where later records will surely turn up. Spring densities were also low in the south (Table 10), but whether this paucity is a matter of the “dilution” of the population in large No. 124 forest acreage or is related in some way to migration route remains to be determined. Philadelphia vireos were more numerous on the eastern than on the western side of the state both in the central and southern regions. They were found in all woody habitats in the central region, but in the south were absent from pines (Pinus taeda) and upland forest (Table 10), though these absences may be spurious in view of the generally low numbers everywhere in the south. Forest edge and shrub appeared to be the preferred habitat in both cen- tral and south. Swink (1976) at Morton Arboretum and Widmann (1907) in Missouri noted that Philadelphia vireos preferred thickets along streams. Philadelphia vireos sing during their spring sojoum even in southern II]linois, but the song is soft and does not greatly increase the species’ conspicuousness. Dwight (1897) described the song as softer, sweeter, and slower (22-36 notes per minute vs 50-70) than the red- eye’s song. Farwell (1919) thought the song less monot- onous than the red-eye’s song. All references to the breeding of the Philadelphia vireo in Illinois (Brewster 1880; Ridgway 1889; Dwight 1897; Gault 1901la; and others) probably refer to E.W. Nelson’s report of two pairs in dense thicket on Mazon Creek on | July 1874 (Cory 1909). This record—if true— would have been far south of the present breeding range (Fig. 23). Swumberg’s (1879) reference to eggs of the Philadelphia almost certainly refers to a traded set, not to a local (Galesburg) collection. Fall Migration By August, Philadelphia vireos are coming back south and have reached the northern region (Daven- port) by at least 14 August (Kleen 1978), the central region by 2] August (Kleen 1979c), and the south by 16 August (Kleen 1977). The earliest television tower casu- alties were found on 29 August at Orion (northwestern Illinois) and 2 September in east-central Illinois (Seets & Bohlen 1977). Peak numbers of Philadelphia vireos have been seen during the period 1-27 September in the northern (four to eight per day) and central (five to nine per day) regions, but in the south no more than one to two per day have been seen in fall (Fig. 22). Ridgway (1874, 1889) called it common or abundant, but gave no numbers; the comment may reflect annual variauon— 1.e., a particularly high year. Both the field counts and our censuses, as well as tower-kill data, indicate that the species is less common in the south than in the central or northern regions (Fig. 22, Table 10). Philadelphias frequented all woody habitats in the central region, where forest edge and shrub was most favored. In the south they were in bottomland forest (Table 10). The latest reports of Philadelphia vireos were 12 and 22 October in the north (Blake & Smith 1942; Fawks 1968a; Bohlen 1978), 13 and 16 October in central IIli- nios (Kleen 1979b; H.D. Bohlen unpublished 1981) plus a straggler on 17 November at Charleston (Kleen 1980b), and 9 and 10 October in the south (Fig. 22). ~ August 1985 Graber, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS ~ 10 NORTH 1@) 1@) TV KILLEXY Q O 0 60 |! CENTRAL I | \ BIRDS COUNTED PER DAY APR MAY JUN JUL AUG SEP OCT SOUTH ‘ is is TV KILLS ! \/ 24 «12 24 12 2 ped 2-28 12 24 12 2h a2 ee APR MAY JUN JUL AUG SEP OCT Fig. 22.—Migration seasons of the Philadelphia vireo in different regions of Illinois (see Fig. 4 for regions). Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Dash lines show numbers killed at television towers during fall migration. Taste 10.—Spring and fall population densities of the Philadelphia vireo in Hlinois (1979-1981) County Number Cumulative : OL of Pechares Birds per 40.5 ha Season and Habitat Region Censuses Censused Maximum Mean Spring (9-24 May) Mature bottomland forest Piatt (C) 6 125 9.2 3.2 Mature bottomland forest Johnson (S) 2 i] 2.1 10 Mature upland forest Piatt (C) 7 159 0 0.5 Mature upland forest Pope (S) 5 64 0 Forest edge and shrub Piaut (C) 5 99 i 9 Forest edge and shrub Pope (S) 1 74 2.5 ey Loblolly pines Pope (S) l 18 0 Fall (2 September—10 October) Mature bottomland forest Piatt (C) 18 262 5.8 14 Mature bottomland forest Johnson (S) 4 200 5.5 04 Mature upland forest Piau (C) ld 271 8.5 1.6 Mature upland forest Pope (S) 11 251 0 Forest edge and shrub Piaut (C) 15 209 10.6 2.6 Forest edge and shrub Pope (S) 13 262 0 Loblolly pines (1979-1980 only) Pope (S) 6 106 0 28 ILLINOIS NATURAL HisTORY SURVEY BIOLOGICAL NOTES ~_ Philadelphia eect} OK Ranges BREEDING EE] winter Ty iso 2 100 400 so olen eo of Geography -Unry_ of Iihinows 10" Fig. 23.—General distribution of the Philadelphia vireo. The ratio of spring to fall counts was 1.0 to 2.6 in the northwest, 1.0 to 1.0 in the central region (1.0 to 2.0 in the census transects), and 4.3 to 1.0 in the south (1.0 to 1.0 in the transects). At Chicago, Dreuth saw Phila- delphias with equal frequency, spring and fall (Clark & Nice 1950), and at Davenport, Petersen banded 1.0 in spring to 1.3 in fall (Dinsmore et al. 1984). In a sample of 39 Philadelphia vireos picked up 2 September—6 October 1957-1972 at central Illinois television towers, there was 1.0 adult to 1.2 immatures, the rough equiva- lent of | bird in spring to 2 in fall. Our only observations on the food of the Philadel- phia vireo were of a bird which—on 18 September—ate two fruits of the dogwood, Cornus racemosa, in quick succession, though the fruit was a bit large and difficult to swallow, and of another, on | October, which skill- fully unrolled the leaf roll on a shingle oak and ate the larva it contained. Chapin (1925) found the diet in- cluded high levels of beetles as well as lepidopterans. Specimen Data An immature male killed on 2 September at the Fithian television tower still showed signs of the body molt. Ranges of gross weights (with mean and standard error) of Philadelphia vireos killed at central Illinois No. 124 towers, 2 September—-6 October 1957-1972 were, for six adult males, 12.7-15.9 g (13.48, 0.49); six immature males, 11.3-13.5 g (12.42, 0.32); six adult females, 10.6— 13.1 g (12.0, 0.39); and six immature females, 11.3—-16.7 g (13.40, 0.82). Brains of Philadelphia vireos were rela- tively heavier than brains of red-eyed vireos (Graber & Graber 1965). RED-EYED VIREO (Vireo olivaceus) (Fig. 24 and cover) Spring Migration The earliest reports of red-eyed vireos in Illinois were: 9-12 April in the south (Fig. 25; Cooke 1883; Hanselmann 1963-1964, Peterjohn 1981), 19-20 April in the central region (Bohlen unpublished 1977, 1981; Cooke 1909), and 14 April in the north (Smith 1941). Cooke (1884a) considered the red-eye to be the slowest spring migrant in the Mississippi Valley. The inference is that red-eyes tend to stay longer at their landing sites than most species, but this behavior apparently has never been confirmed by observations of banded birds. Peak numbers of red-eyes have been seen 30 April-21 May in the south (29-42 per day), 10 May—2 June in the central region (30-60 per day), and 14 May—5 June in the north (15-28 per day) (Fig. 25). Cooke (1883) called the species common in the south on 12 April, an early date for the species to appear in numbers. The counts for the north represent primarily northwestern Illinois, and we would expect higher numbers in the northeast, where birds may be concentrated along the Lake Michi- gan shore. The passage of the last transients, especially in the north and central regions, may be obscured by the sizable breeding population in the area, but we suspect that the last females may not pass northern Illinois unul late June in some years. Twomey (1945) noted that red-eyes in spring at Tre- lease Woods (east-central) tended to stay in the forest interior, where counts were 35-40 birds per day, versus 10-15 for forest edge. Our data (Table 11) show the same preference by red-eyes in southern as well as cen- tral Illinois. Spring densities were higher in bottomland than upland forest in the south, but this “preference” was reversed in the central region (Table 11). Average spring densities ranged from about two times (upland forest, south) to about nine umes (upland forest, cen- tral) average June densities in the same habitats (Tables 11 and 12). In all habitats combined there were 4.6 umes as many red-eyes in May as in June, indicating a large transient population. For purposes of comparison, the ratio is from our transect censuses only. In the south, spring counts tended to be higher on the western side of the state (1.5 times) than on the east, but in central Illinois the pattern was reversed—1.0 (west) to 1.8 (east)—judging from dates with counts available for both sides (see also Fall Migration). sugust 1985 Graber, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS Fig. 24 —Red-eyed vireo at its nest, 3 June 1975 1n Pope County 30 ILLINOIS NATURAL History SURVEY BIOLOGICAL NOTES No. 124 O 20 o 6 © NORTH EGG DATES 10 12 24 JUL AUG 1225 JUN 2 24 12 24 pie Ff SEP » 171 Oh L024 60 (e) 2) 3 CENTRAL i N= TV KILLS 40 0 mie APR MAY 20 10 BIRDS COUNTED PER DAY 12 24 12 24 12 24 12 24 1228 12 2h i APR MAY JUN JUL AUG SEP OCT 12 24 12 24 In 2h a12e2h 123424 12.24 32 APR MAY JUN JUL AUG SEP OCT Fig. 25.—Egg-laying and migration seasons of the red-eyed vireo in different regions of Illinois (see Fig. 4 for regions). Spring and fall lines show the highest daily count of each 3 days (1967-1970). Hollow circles represent counts made in other years or by other observers. Shaded areas show the span of dates during which eggs have been recorded. Dash lines show numbers killed at television towers during migration. | ) August 1985 GRABER, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 51 Taste 11.—Spring and fall population densities of the red-eyed vireo in Hlinois (1979-1981). County Number Cumulative é sy aI recites Birds per 40.5 ha Season and Habitat Region Censuses Censused Maximum Mean Spring (9 April-31 May) Mature bottomland forest Piatt (C) 8 166 11.8 21.4 Mature bottomland forest Johnson (S) 20 116 11.2 12.9 Mature upland forest Piatt (C) 12 259 69.3 30.3 Mature upland forest Pope (S) 21 133 28.8 8.7 Forest edge and shrub Piatt (C) 9 183 28.5 10.6 Forest edge and shrub Pope (S) 17 337 8.0 1.8 Loblolly pines Pope (S) 10 179 11.3 2.0 Fall (20 August—11 October) Mature bottomland forest Piatt (C) 17 344 35.0 8.1 Mature bottomland forest Johnson (S) 16 333 9.8 Bj Mature upland forest Piatt (C) 19 368 18.5 11.8 Mature upland forest Pope (S) 15 327 5.5 0.7 Forest edge and shrub Piatt (C) 20 399 47.8 13.6 Forest edge and shrub Pope (S) 17 346 8.0 1.3 Loblolly pines (1979-1980 only) Pope (S) 8 142 0 Distribution The red-eyed vireo has an extensive range in North America (Fig. 26; Pitelka 1941) that includes both deciduous and coniferous forest areas. In Illinois the species surely nests in every county and probably in nearly every township. The absence of records for large areas of the state (Fig. 27) almost certainly indicates inadequate exploration in those areas. In addition to records plotted in Fig. 27, there are breeding records for unspecified localities in Piatt, Champaign (Goelitz 1917), Knox (Holland unpublished 1952), Peoria, Shelby, and Warren counues (Greenberg 1982). Nesting Habitats and Populations Red-eyed vireos have occupied a rather broad range of woods habitats in Illinois, including young stands (Brewer 1958) as well as extensive mature upland and bottomland forest (Table 12; Cahn & Hyde 1929). Red- eyes have also been found in a small grove in prairie (Birkenholz 1975), human residential areas (J. Ridgway 1923; R. Ridgway 1887, 1925b; Silloway 1894b; Roberts 1923; Beecher 1942), city parks (Ford 1915; Nice 1950, 1952), and an urban cemetery (Zimmerman & Steffen 1975). Populations in human residential areas are prob- ably very low. Most of our censuses in towns have been negative for the species, and even in Ridgway’s (1887) time red-eyes were on the outskirts of town and sparse even there. In southern Illinois, where we censused a total of 441 acres (178 ha) of residential habitat in 1958, 1976, and 1977, no red-eyed vireo was detected in the transect. The species may be more likely to occur in northern towns, where we found a density of one bird per 40 ha in 1958 (Table 12). Even in forest proper, densities appear to be higher in the north than in the central and south (Table 12). Forest edge is also poor habitat, having consistently low densities of red-eyed vireos (Table 12). Kendeigh (1982) showed that red-eyed vireo numbers decreased when forest canopy was disrupted. In recovering strip- mined land, where Brewer (1958) studied plots ranging in age from 6 to 24 years after suipping, he found red- eyes only in the oldest plots (21-24 years), where tree crowns were apparently sufficiently developed for the species. The highest average densities of red-eyed vireos on record (31-38 birds per 40.5 ha) were in upland forest of east-central Illinois, bottomland forest having slightly lower numbers (Table 12). Densities for large areas cen- sused by transect census in June only were much below those in which map censuses were applied. The map censuses generally contained spring (April—May) data, possibly including some transients. Our densities for spring are more nearly comparable to the map census results (Tables 11 and 12). Our censuses also show higher breeding densities in bottomland than in upland forest in both southern and central Illinois (Table 12). Gates (1911) considered the red-eyed vireo a dominant species of bottomland forest on the Illinois River. Swink (1976) felt that the preferred habitat at Morton Arboretum was woods of mature white oak and sugar maple. Of 45 plants identified as nest sites of red-eyed vireos in all regions of Illinois, 19 were maples, including at least 10 sugar maples; 5 were ironwoods; 4 hackberries (Celtis sp); 3 white ashes (Fraxinus americana); 2 lindens (Tilia americana); 2 ‘oaks’; and 1 each of sassafras, black locust (Robinia pseudoacacia), elm, sycamore (Platanus occidentalis), grape (Vitis sp), honeysuckle, witch hazel, choke cherry, blackberry, and redbud. Original citauions for some of these plants lack scien- ufic names. The high percentage of sugar maples sug- gests a preference by red-eyes for mesic upland woods. Red-eyed vireo densities were not correlated with Impor- tance (Y) of Acer or any other plant in the various forest tracts we studied (Graber et al. 1977, 1983), but the areas with lowest Y (0-2) for Acer also had the lowest densi- ties of red-eyes. Heights of 50 Illinois nests ranged from 2 to 45 feet (1-14 m), with modes at 6—10 feet (2-3 m) and 20 feet (6 m) and an overall average of 11.1 feet (3.4 m). The data probably underrepresent high nests. 32 » ILLINOIS NATURAL HistToRY SURVEY BIOLOGICAL NOTES TABLE 12.—Breeding populations of red-eyed vireos in various IIlinois habitats. Habitat Urban residenual Woods (unspecified) Forest (all types, including edge) Forest (all types, including edge) Forest (all types, including edge) Forest (all types, including edge) Virgin floodplain forest Virgin floodplain forest Floodplain forest Bottomland forest Bottomland forest Mature bottomland forest Grazed stream bottomland forest Mature bottomland forest Riparian oak-hickory forest Oak-maple forest Upland forest Upland oak-hickory forest Mature upland forest Oak-hickory-maple forest Mature upland forest Upland deciduous forest Second-growth hardwood Cutover upland oak-hickory forest Abandoned farmland (shrub and forest edge) Shrub, including edge shrub Pastures Pastures Birds per 40.5 ha 1 19.2 11-14 (avg 12.4) 3-7 (avg 5.1) 5-8 (6.7) 7-8 (avg 7.6) 20 24 8-72 (avg 27.2) 26 7.3-14.6 (avg 11.0) 024.4 (avg 6.1) 22.6 0-30 (avg 5.3) 4b 6.7-80.9 (avg 30.7) 32.258. 1 (avg 37.6) 4.2 0-6.3 (avg 3.3) 6.2-25 (avg 17.5) 0-11.5 (avg 4.5) 13.2-26.3 (avg 19.7) 26.7 4.1-30.6 (avg 11.7) 0-H (avg 0.3) (+1 (avg 0.8) 1 0+ “Strip censuses calculated as cumulative hectares. >+ = less than one bird per 40.5 ha. Years 1958 1914-1923 1957-1958 1957-1958 1907-1908 1957-1958 1948 1947 1949-1951, 1963, 1967 1966 1974, 1978 1978-1981 1955 1973-1981 1980 1927-1976 (42 years) 1949-1951, 1962, 1964, 1966 1967 1978-1981 1977-1981 1974-1981 1977-1978 1937 1941-1942, 1944, 1948 1953-1969 1971 (18 years) 1957-1958 1909 1907, 1909 County or Region North Rock Island (N) North Central South South Sangamon (C) Piatt (C) Piatt (C) Vermilion (C) Willow Slough, Indiana Central Macon (C) South Wayne (S) Champaign (C) Piatt (C) Hancock (C) Central McLean South Jackson (S) Rock Island (N) Sangamon (C) Piatt (C) South North Central Hectares Censused 65° 8-22 72 87 24 Type of Census Strip Strip Suip Strip Strip Map Map Map Map Map Suip Map Suip Map Map Map Map Suip Map Strip Map Map Map Map Sup Suip Suip Reference Graber & Graber 1963 J.J. Schafer unpub- lished notes Graber & Graber 1963 Graber & Graber 1963 Graber & Graber 1963 Graber & Graber 1963 Snyder et al. 1948 Fawver 1947a Kendeigh 1982 Karr 1968 Hopkins 1974, 1978 This paper Chaniot & Kirby 1955 This paper Keener 1981b Kendeigh 1982 Kendeigh 1982 Franks & Martin 1967 This paper Birkenholz 1977, 1978, 1979, 1980, 1981 This paper Morrison & Peterjohn 1977; Morrison 1978 Fawks 1937 Robertson 1941, 1942, 1944; Robertson & Snyder 1948 Kendeigh 1982 Graber & Graber 1963 Graber & Graber 1963 Graber & Graber 1963 August 1985 ae. So f=, Red-eyed Vireo Fig. 26.—General distribution of the red-eyed vireo. No particular trend is apparent in the available data on the question of whether or not the red-eyed vireo population is changing (Table 12). Ridgway (1889) considered it the most abundant woodland species. Eifrig (1937) thought the red-eye population was declin- ing in Illinois because of cowbird depredations, but the case has not been proved. Territories of red-eyed vireos were measured in two habitats in Piatt County in 1946. In virgin floodplain forest six territories averaged 3.1 acres (1.2 ha) (Fawver 1947a), and in upland forest four territories ranged in size from 0.7 to 2.5 acres (0.3-1.0 ha) and averaged 1.7 acres (0.7 ha) (Allison 1947). In mature bottomland forest in McLean County four territories (each year) ranged from 0.58 to 2.53 acres (0.2—1.0 ha), with a mean of 1.43 acre (0.6 ha) in 1950, and from 1.92 to 2.60 acres (0.8—1.0 ha), with a mean of 2.36 acres (0.95 ha) in 195] (Calef 1953). Calef observed that territory size increased when the red-eye population decreased. Allison (1947) observed a red-eyed vireo whose territory was within the boundaries of a yellow-throated vireo’s territory, the two species being enurely compatible. In a Chicago park a red-eyed vireo defended an area of about 0.7 acre (0.3 ha) from grackles, but defended 1.8 acre (0.7 ha) from another red-eyed vireo (Nice 1950). GRABER, GRABER, & KIRK: ILLINOIS BIRDS: ViREOS 33 Red-eyed Vireo NESTS OR YOUNG @ = 1950- A= 1900-1949 @= Before 1900 JUNE RECORDS o= 1950- A= 1900-1949 O= Before 1900 Fig. 27.—Breeding records of the red-eyed vireo in Illinois Nesting Cycle The red-eyed vireo is one of the most persistent sin- gers, the male singing usually in the upper canopy even at midday of the hottest season (Widmann 1907; Two- mey 1945). The song is a pretty series of somewhat ques- tioning phrases, sometimes phoneticized: ‘Do you heat me? Do you see me? Lam here . . . .,"" often continuing on and on with variations on the theme. Nice (1950) observed the rate of singing to be consistent for a par- ticular male, but that it varied from male to male. At Chicago one male sang 57 times per minute, another 35 (Nice 1950). In east-central Illinois the main song period lasted until early August (Fawver 1947b). At St. Louis, Widmann (1907) noted that singing was inter- rupted 5-6 weeks in late summer—probably during the 34 ILLINOIS NATURAL History SURVEY BIOLOGICAL NOTES molt. Our notes indicate that song ended in all regions finally during the last half of September and that birds were relatively quiet in July and early August. Another common vocalization is a grating scold note uttered over and over when intruders are near the nest. Nest building activity by red-eyes may be seen nearly any time in summer, but in southern Illinois it occurs particularly during May. Even in the north many first nests are completed by 5 June. More coarse in structure than nests of the smaller vireos, the nest of the red-eye is a relatively shallower, wider bowl. Crone (1896) de- scribed one made of grass, spider web, and bits of hornet’s nest. Nice (1950) observed that only the female brought material (shreds from a willow) during nest construction, though the male accompanied her on 15 of 16 trips she made in an hour. The female built with a weaving motion for periods of a few seconds to 2 min- utes. Hess (1910) suggested that red-eyes build ‘‘extra”’ nests, based on the number of unoccupied nests he found, but the point needs verification. The eggs are white lightly speckled with brown. The laying season extends from at least 12 May in cen- tral Illinois to at least as late as 5 August in the north (Fig. 25). A nest with four young on 15 May in central Illinois (Hess 1910) implies a laying date at least as early as 2-3 May (not plotted in Fig. 25)—probably excep- uonally early for the species at that latitude, though earlier laying records can be expected in southern IIli- nois when the data are more complete. In Canada, Lawrence (1953) determined the incuba- tion period to be 12-14 days, most commonly 13. Incu- bation was by the female only. At Chicago attentive periods by the female ranged as high as 30 minutes. She was off the nest for periods of 7, 11, and 1 minute between attentive periods during the incubation phase, while the male defended the nest area—chasing grackles away 16 times in 80 minutes (Nice 1950). The red-eye is a frequent victim of cowbird parasit- ism (Friedmann 1963), and clutch size depends very much on the amount of such interference (Table 13). In 12 nests studied by Twomey (1945) the clutch size of the red-eyed vireo averaged 3.25 (+ 1.08 cowbird eggs). Within historical times the parasitism rate in this spe- cies has been high (Crone 1896; Sanborn & Goelitz Tasre 13.—Clutch size in Illinois red-eyed vireos, Data represent all regions between 1884 and 1981. Not Parasitized Parasitized Cowbird Eggs Clutches Eggs — Clutches Vireo Eggs l 2 3 i ] 5 1 5 + ] 0 0 0 12 1 3 1 1 A 0 | 0 ] iS 16 5 T LO 1 2 0 0 2 9 2 + 4 3 2 0 0 ] 2 l + 0 l l 0 0 0 3 0 (0) 0 2 | Total nests: 14 34 fverage vireo clutch: 4.0 2. dverage cowbird clutch: 0 1.8 No. 124 1915). Poling (1889) found four of six nests parasitized. The red-eye is one vireo that can raise young of its own and cowbirds together. A Pope County nest that we observed fledged three vireos and one cowbird. Lawrence (1953) found the duration of nestling life to be 10-11 days. At Chicago, Nice (1950) observed that both adults fed the young. When nestlings were 1-2 days old, the female brooded 40 minutes between 1000 and 1100 hours and brought food once, while the male brought food twice. The next day between 0630 and 0730 the male fed nestlings once, and the female fed them five times and brooded for 1-20 minutes after each feeding. In general, males did much less of the feeding of nestlings than did females (Lawrence 1953). Cowbird parasitism has a strong influence on pro- ductivity in red-eyed vireo populations. Nesting suc- cess in parasitized nests was half or less that in unpara- sized nests (Friedmann 1963). The 12 nests studied by Twomey (1945) produced, on average, 1.7 vireos and 0.8 cowbird per nest. Nine of his nests produced at least one vireo—a high rate of success. Calculations of success by the exposure method (Mayfield 1961, 1975) were not in use at that me. In a sample of 16 recent Illinois nests (all regions) only one (6 percent) fledged young—three vireos and one cowbird. Such a rate would be insuffi- cient to support a population, and the sample may represent particularly vulnerable nests. Studies are needed for larger samples of nests over a period of years—nests that represent different habitats and all parts of the nesting season. Late nests (after June, 1.e., after the cowbird laying season) may be more successful. Causes of nest failure are unknown on any quantitative basis. Nice’s (1950) observations imply problems with avian predators. At least 3 nests of 48 for which partial histories are available were robbed of eggs or nestlings by blue jays (Mrs. W. Carroll unpublished 1964, 1967; M. Easterday unpublished 1978). The long laying season (Fig. 25) may imply that red-eyes try for more than one brood, but verification from studies of banded birds is required. B.T. Gault (unpublished 1897, 1899) saw young sull in the care of adult birds as late as 13-17 September in northeastern Illinois. Late nestings may merely reflect the large number of nest failures 1n this species. We have seen red-eyed vireos in heavy molt on 11 August, as did Ferry (1907), and birds that appeared to be in fresh plumage, as well as some sull molting, on 21 August in the south. In the north most appeared to be in fresh plumage by 27 August. At least five adult red- eyes from central Illinois television tower kills were sull in molt (crown, breast, and wings) on 17 September. Another was sull in worn plumage on 29 September. Fall Migration Tower-kill data indicate that the fall migration of red-eyed vireos is in progress at least as early as 24 August in central Illinois (Fig. 25). Musselman (1937) reported ‘‘a small flight’ of red-eyes on 23 August at August 1985 Quincy. Red-eyes seen out of habitat by Gault (unpub- lished 1916) on 14 July at Glen Ellyn could have been either migrants or local breeders moving about. Peak numbers of red-eyes (9-16 per day) have been seen in northwestern Illinois, 1-24 September (Fig. 25; Brown 1968), but P.C. Petersen banded highest numbers at nearby Davenport in late August (Halmi 1977). In the central region peak numbers (17-65 per day) were seen 23 August—-4 October, with high numbers of tower- killed birds between 2 September and | October. In the south highest numbers (7-11 per day) were seen | August—17 September, with highest numbers picked up at the towers 22 September—6 October (Fig. 25). Note that both the counts and tower kills were lower in the south than in the central region. Probably because of its extensive range and high populations north of Illinois, the red-eyed vireo is one of the commonest victims at television towers (Brewer & Ellis 1958)—at least 1,091 specimens having been picked up in central and south- ern Illinois since 1957. As only a few towers are checked, none on a regular daily basis, the total kill of red-eyes in the state is likely many umes that number. The last red-eyed vireos of the season were seen 19 and 24 October in the north (Boulton & Pitelka 1938b; Clark & Nice 1950; Kleen 1975a), 25 October and 9 November in the central region (Fig. 25; Bohlen unpub- lished 1975), with one straggler as late as 30 November (Kleen 1974a), and 21 and 24 October in the south (George 1968; tower specimen 1975). A possible indication of the direction of fall migra- tion comes from a red-eye banded near Manitowoc, Wisconsin, on 11 September 1966 and recovered dead at the Seymour, Illinois, tower (330 miles [531 km] south of banding site) on 21 September 1966. Twomey (1945) noted that red-eyes made greater use of forest edge (versus interior) in fall than in spring, as did we in central Illinois (Table 11). Otherwise red-eyed vireo habitats in fall were similar to those used in spring, but with generally lower densities in fall. The ratio of our counts—spring to fall—was 1.1 to 1.0 in the northwest. At Chicago, Dreuth saw red-eyes with a fre- quency ratio of 1.0 to 1.6, and at Davenport, P.C. Petersen banded nearly twice as many red-eyes in fall as in spring. In the central region the ratio was 1.2 to 1.0 (1.0 to 1.0 in the census transects), but in the south it was a lopsided 5.6 to 1.0 (6.2 to 1.0 in the transects). The sharp difference in the south is possibly related to dif- ferences in migration route between spring and fall, but that theory needs verification. The matter is further complicated because of differences in the numbers of red-eyes seen on the eastern and western sides of the state. In the central region counts were not radically different (1.0 to 1.8) between west and east in spring, but in fall about four times more red-eyed vireos were seen in the east. This is a pattern seen in a number of migrant species (Graber et al. 1983). The ratios of the spring-fall counts do not account for any productivity by red-eyes during the nesting sea- son, though both Dreuth's counts (Clark & Nice 1950) GRABER, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 35 and Petersen’s banding data (Dinsmore et al. 1984) showed better fall ratios and would account for some production. Age ratios in our sample of 262 tower- killed birds also indicate some productivity, but with results differing early and late in the fall migration. Ina sample of 196 red-eyes killed by 21 September (over the years), there were more adults (99) than immatures (97), 1.02 adults to 1.00 immature. In a sample (66) killed after 21 September over the years, there was 1.0 adult to 3.7 immatures, and the only October specimens (7) had a ratio of | adult to 6 immatures. Many birds of the year pass through the state late in the season. The age rauo in the overall sample (1.00 adult to 1.32 immatures) would be the hypothetical equivalent of about | bird in spring to 2.3 in fall. Food Rice’s (1946) study of food remains in six red-eyed vireo stomachs, representing spring, summer, and fall specimens, showed Lepidoptera to be the most common food, especially in summer. Diptera and Coleoptera (in both spring and fall) were next in importance. A stom- ach examined by Forbes (1878) also contained Lepidop- tera (larva). We have often seen red-eyes feed on caterpil- lars both in spring and fall. Red-eyes were the com- monest avian predators on larvae of Lithophane sp and Morrisonia distincta during an irruption of these lepi- dopterans on silver maples in the Sangamon (and other river) bottoms in May 1979. Hulsberg (1917-1918) ob- served red-eyes feed on egg masses of the tussock moth, and at least once (15 September) we saw a red-eyed vireo eat a furry tussock larva. More often in fall we have seen red-eyes feeding on fruit, including elderberries (Sam- bucus canadensis)—see also Ridgway (1915a)—wood- bine (Parthenocissus quinquefolia), black cherry (Pru- nus serotina), wild grape, pokeberries (Phytolacca amer- icana), and multiflora rose (Rosa). We did not see the vireo swallow the rose hip, but the other fruits were swallowed—probably with difficulty—except for elder- berry and woodbine. Because the fruit in a large head of elderberry may be difficult to reach, red-eyes sometimes flutter in front (below) the head and pick the fruit on the wing. Chapin (1925) found that up to 49 percent of the red-eye’s food in October is vegetable—wild fruit— whereas through April—October, overall, about 85 per- cent of the food is made up of insects, with Lepidoptera predominating. Specimen Data Ridgway (1904) noted that red-eyed vireos from the Mississippi Valley were intermediate in size between smaller birds from the Atlantic coast and larger ones from the Rocky Mountains. No subspecies was recog- nized by the American Ornithologists’ Union (1957). Ranges of gross weights (with mean and standard error) of fresh specimens of red-eyed vireos killed at central Illinois television towers, 9 September—15 Oc- tober, 1957-1972, were, for 20 adult males, 15.5-21.8 g (19.35, 0.38); 36 immature males, 16.8-24.7 g (19.52, 36 ILLINOIS NATURAL History SURVEY BIOLOGICAL NOTES 0.34); 28 adult females, 15.7-21.9 g (18.79, 0.24); and 32 immature females, 15.9-24.6 g (19.22, 0.35). Most of the specimens were moderately fat (2-3 on a scale of 0-5). Immatures were generally fatter than adults, and some r immatures were extremely fat (5). The spring data— specimens killed 20-22 May—includes Hancock’s (1888) specimens. For two males gross weights were 19.3 g (fat class 3) and 23.0 g; for four females 20.2 g (fat = 3), 20.8 ¢ (fat = 3), 19.7 g, and 15.4 g. Brain weights of red-eyed vireos were given by Hancock (1888) and Graber & Graber (1965). LITERATURE CITED Atuison, D.G. 1947. Bird populations of forest and forest edge in cenual Illinois. M.S. Thesis. University of Illinois. 87 p. AMERICAN ORNITHOLOGISTS’ UNION. 1957. Check-list of North Ameri- can birds. 5th ed. American Ornithologists’ Union, Baltimore, MD. 691 p. AMERICAN ORNITOLOGISTS’ UNION. 1983. Check-list of North Ameri- can birds. 6th ed. American Ornithologists’ Union, Lawrence, KS. 877 p. ANpeRSON, R.A., and P.E. Bauer. 1968. A guide to finding birds in the St. Louis area. Webster Groves Nature Study Society. 44 p. Battow, W.H. 1878. Things oological. Ornithologist and Oologist 4(5):33-34. Barnes, R.M. 1890. List of birds breeding in Marshall Co., Il]. Orni- thologist and Oologist 15(8): 113-116. BEECHER, W.J. 1942. Nesting birds and the vegetation substrate. Chi- cago Ornithological Society, Chicago. 69 p. BELLROsE, F. 1936. Notes from north central Illinois. Auk 53(3):348. Bent, A.C. 1950. Life histories of North American wagtails, shrikes, vireos, and their allies. U.S. National Museum Bulletin 197. 411 p. BIRKENHOLZ, D.E. 1975. The summer birds of Goose Lake Prairie Nature Preserve. Chicago Academy of Sciences Natural History Miscellanea 193. 11 p. . 1977. 40. Oak-hickory-maple forest. American Birds 31(1):43. ——____.. 1978. 38. Oak-hickory-maple forest. American Birds 32(1):66 —_—___.. 1979. 34. Oak-hickory-maple forest. American Birds 33(1):65 —____.. 1980. 33. Oak-hickory-maple forest. American Birds 34(1):52 . 1981. 40. Oak-hickory-maple forest. American Birds 35(1): 59-60. BJORKLUND, R. 1979-1980. Nesting solitary vireo in central Illinois. Illinois Audubon Bulletin 191:21-23. . 1980-1981. Observational evidence for homing in birds. IIli- nois Audubon Bulletin 195:27-28. Biake, E.R., and E.T. Smiru. 1942. Chicago region. Audubon Maga- zine 44(2):9 (supplement). Bouten, H.D. 1978. An annotated check-list of the birds of Illinois. Illinois State Museum Popular Science Series 9. 156 p. Bouton, R., and W.J. BEECHER. 1939. Chicago region. Bird-Lore 41(6):10-11 (supplement). , and F.A. PiTecka. 1938a. Chicago region. Bird-Lore 40(4): 290-291. , and . 1938b. Chicago region. Bird-lore 40(6):464—465. BREWER, R. 1955. Size of home range in eight bird species in a south- ern Illinois swamp-thicket. Wilson Bulletin 67(2):140-141. . 1958. Breeding-bird populations of strip-mined land in Perry Co., Ill. Ecology 39(3):543-545. ,and J.A. Extis. 1958. An analysis of migrating birds killed at a television tower in east-central Illinois, September 1955—May 1957. Auk 75(4):400-414. ,and W. Harpy. 1950. 18. Swamp and thicket. Audubon Field Notes 4(6):303. Brewster, W. 1880. Notes on the habits and distribution of the Phila- delphia vireo (Vireo philadelphicus). Nuttall Ornithological Club Bulletin 5(1):1-6. No. 124 Bropkors, P. 1926. Chicago region. Bird-lore 28(6):407-408. . 1930. Notes on some birds uncommon in northern Illinois. Auk 47(4):577-578. Brown, W.H. 1968. Field reports. lowa Bird Life 38(4):123—127. Butter, A.W. 1891. A catalogue of the birds of Indiana. Indiana Horticultural Society Transactions, 1890 [Appendix C]. 135 p. Cann, A.R., and A.S. Hype. 1929. Easter birds of Little Egypt. Wilson Bulletin 41(1):31-38. Cater, R.T. 1953. Avian populations of the Funk Forest Natural Area in McLean County, Illinois. Illinois State Academy of Science Transactions 46:240-257. Cuaniot, G., and R. Kirsy. 1955. 4. Grazed stream bottomland. Audubon Field Notes 9(6):413. Cuapin, E.A. 1925. Food habits of the vireos. U.S. Department of Agriculture Bulletin 1355. 42 p. Cuase, V. 1899. A Chicago park honzon. Wilson Bulletin 11(3):40. Crark, C.T., and M.M. Nice. 1950. William Dreuth’s study of bird migration in Lincoln Park, Chicago. Chicago Academy of Sciences Special Publication 8. 43 p. Comrort, J.E. 1942. Webster Groves notes. Bluebird 9(5):28. Cooke, W.W. 1883. Mississippi valley migration. Ornithologist and Oologist 8(12):89-91. —____ . 1884a. Migration in the Mississippi valley. Ornithologist and Oologist 9(1):1-2. —____.. 1884b. Curious nest of the warbling vireo. Ornithologistand Oologist 9(9):111. . 1885. Mississippi valley migratlon—spring 1883. Ornitholo- gist and Oologist 10(11):161—163. . 1888. Report on bird migration in the Mississippi valley in the years 1884 and 1885. U.S. Department of Agriculture, Divi- sion of Economic Ornithology Bulletin 2:313 p. . 1909. The migration of vireos. Bird-Lore 11:78-82, 118-119, 165-167. , and O. WipMANN. 1884. Bird migration in the Mississippi Valley. American Field 21(1):9. Cory, C.B. 1909. The birds of Illinois and Wisconsin. Field Museum of Natural History Publication 131, Zoological Series Vol. 9. 764 p. Crone, J.V. 1896. Notes on the birds of Iowa. Iowa Ornithologist 2(2):4048. CUNNINGHAM, J.W. 1943. St. Louis area notes. Bluebird 10(8):47. Dinsmore, J.J., T.H. Kent, D. Koenic, P.C. PETERSEN, and D.M. Roosa. 1984. Iowa birds. Iowa State University Press, Ames. 356 p. Du Bots, A.D. 1940. Nesting habits and behavior of Bell's vireo. Audubon Bulletin 35:1-8. Du Mont, P.A. 1936. Old nesting records of rare birds in Iowa. Oolo- gist 53(1):8-10. . 1947. Middlewestern region. Audubon Field Notes 1(5): 177-179. Dwicut, J. 1897. A study of the Philadelphia vireo (Vireo philadel- phicus). Auk 14(3):259-272. E1FerT, V.S. 1949. A lake for the Lincoln country. Audubon Magazine 51(4):218-225. E1rric, C.W.G. 1937. The changing status of birds as regards their abundance. Illinois State Academy of Science Transactions 30(2):295-297. E1rric, G. 1915. Field notes from the Chicago area. Wilson Bulletin 27(3):417A19. Etuiott, A. 1901. Note on the warbling vireo. Bird-Lore 3:175. Farwe.tt, E.D. 1919. Bird observations near Chicago. (Privately printed, Chicago). 188 p. Fawks, E. 1937. Second-growth hardwood. Bird-Lore 39(5):380. . 1938. Second-growth hardwood. Bird-Lore 40(5):359. . 1965. Field notes—winter 1964-65. Audubon Bulletin 133:3—+4. —__— . 1966. Field notes—June 1966. Audubon Bulletin 138:6-8. —_____ . 1967. Field notes—March 1967. Audubon Bulletin 141:12-13. —_____. . 1968a. Field notes. Audubon Bulletin 145:14-16. . 1968b. Field notes. Audubon Bulletin 148:18—20. Fawver, B.J. 1947a. Bird population of an Illinois flood plain forest. Illinois State Academy of Science Transactions 40:178-189. August 1985 . 1947b. The bird and mammal population of an Illinois flood plain forest. M.S. Thesis. University of Illinois. 51 p. Ferry, J.F. 1907. Further notes from extreme southern Illinois. Auk 24(4):430-435. . 1908. The spring migration of 1907 in the vicinity of Chi- cago. Wilson Bulletin 20(1):27—-40. Forses, S.A. 1878. The food of birds. Illinois Horticultural Society Transactions 23:140-145. ——_— . 1883. The regulative action of birds upon insect oscillations. Illinois State Laboratory of Natural History Bulletin 1(6):1-32. Forp, E.R. 1915. Recollections of city bird-nesting. Oologist 32(10):156-157. . 1956. Birds of the Chicago region. Chicago Academy of Sciences Special Publication 12. 117 p. Franks, E.C., and W. Martin. 1967. 6. Upland oak-hickory forest. Audubon Field Notes 21(6):615. FRIEDMANN, H. 1963. Host relations of the parasitic cowbirds. U.S. National Museum Bulletin 233. 276 p. Gates, F.C. 1911. Summer bird life in the vicinity of Havana, Illinois, in its relation to the prominent plant associations. Wilson Bulletin 23(1):1-27. Gautt, B.T. 190la. April and May bird-life at Glen Ellyn (near Chicago), Illinois. Bird-Lore 3(2):65-67. —_—.. 190]b. August and September bird-life at Glen Ellyn (near Chicago), Illinois. Bird-Lore 3(5):166-168. Georce, W.G. 1968. Check list of birds of southern Illinois, 1968. Southern Illinois University, Carbondale. 28 p. (mimeographed) 1971. Vanished and endangered birds of Illinois: a new “black list” and “red list.” Audubon Bulletin 158:2-11. . 1973. Molt of juvenile white-eyed vireo. Wilson Bulletin 85(3):327-330. Goetitz, W.A. 1917. 1916 list of Illinois nests. Oologist 34(5):87. Graber, J.W., and R.R. Graser. 1976. Environmental evaluations using birds and their habitats. Illinois Natural History Survey Biological Notes 97. 40 p. A , and E.L. Kirk. 1977. Illinois birds: Picidae. Illinois Natural History Survey Biological Notes 102. 73 p. ; , and . 1983. Illinois birds: wood warblers. Illinois Natural History Survey Biological Notes 118. 144 p. Graber, R.R., and J.W. Graper. 1963. A comparative study of bird populations, 1906-1909 and 1956-1958. Illinois Natural History Survey Bulletin 28:383-528. , and . 1965. Variation in avian brain weights with special reference to age. Condor 67(4):300-318. , and E.L. Kirk. 1970. Illinois birds: Mimidae. Illinois Natural History Survey Biological Notes 68. 38 p. GREENBERG, M. 1982. 1981 reports and results, mid-June birding challenge. Illinois Department of Conservation Periodic Report 20. 16 p. Hacans, M., and H. SHaw. 1961. Illinois field notes—Fall, 1960. Audubon Bulletin 117:6. Hai, N.S. 1977. Field reports. lowa Bird Life 47(4):142-148. Hancock, J.L. 1888. The relative weight of the brain to the body in birds. American Naturalist 22(258):537-539. HANSELMANN, S. 1963-1964. The warbler and vireo migration in the St. Louis area. Bluebird 30(4):9-12. Henstey, M.M. 1948. Studies of the breeding bird population of the forest-edge in Robt. W. Allerton Park, central Illinois. M.S. Thesis. University of Illinois. 76 p. . 1950. Notes on the breeding behavior of the Bell's vireo. Auk 67(2):243-244. Hess, LE. 1910. One hundred breeding birds of an Illinois ten-mile radius. Auk 27(1):19-32. Heye, P.L. 1963. Tower fatalities. Bluebird 30(1):7. Honces, J. 1951. The breeding birds of Credit Island. lowa Bird Life 21(3):50-51. . 1953. Recent changes in Davenport bird life. lowa Bird Life 23(4):61-64. . 1954. The Burtis H. Wilson journals. Iowa Bird Life 24(2):34-38. Hotcomee, C.E., and C.E. Yeomans. 1938. Illinois. Inland Bird Banding News 10(3):8-9. GRABER, GRABER, & KIRK: ILLINOIS BIRDS: VIREOS 37 Ho ttanpb, H.M. 1923. Cowbird-like behavior of red-winged blackbird. Auk 40(1):127-128. Hopkins, E.M. 1974. 104. Maintained invaded grassland. American Birds 28(6):1033-1034. . 1978. 41. Poorly drained mixed oak forest. American Birds 32(1):67. Hucsserc, E. 1917-1918. Notes from La Grange. Audubon Bulletin, winter: 31. Karr, J.R. 1968. Habitat and avian diversity on strip-mined land in east-central Illinois. Condor 70(4)348-357. Keener, V. 198la. 39. Floodplain forest. American Birds 35(1):59. . 198lb. 41. Riparian oak-hickory forest. American Birds 35(1):60. Kenpeicu, S.C. 1982. Bird populations in east-central Illinois: fluctuations, variations, and development over a half-century. Illinois Biological Monographs 52. 136 p. KENNaARD, J.H. 1975. Longevity records of North American birds. Bird-Banding 46(1):55—73. KLEEN, V.M. 1974a. Middlewestern prairie region. American Birds 28(1):58-63. . 1974b. Field notes. Spring migration. Illinois Audubon Bulletin 170:14-22. 1974c. Middlewestern prairie region. American Birds 28(4):807-810. 1975a. Middlewestern prairie region. American Birds 29(1):64-68. . 1975b. Middlewestern prairie region. American Birds 29(3):696-700. . 1976a. Middlewestern prairie region. American Birds 30(1):77-82. . 1976b. Field notes. Fall migration. Illinois Audubon Bulletin 176:28-36. . 1976c. Field notes. Spring migration. Illinois Audubon Bulletin 178:25-35. . 1976-1977. Field notes. Breeding season. Illinois Audubon Bulletin 179:34—40. . 1977. Field notes. Fall migration. Illinois Audubon Bulletin 180: 36-46. . 1977-1978. Field notes. Breeding season. Illinois Audubon Bulletin 183:30-37. . 1978. Middlewestern prairie region. American Birds 32(2):210-215. . 1978-1979. Field notes. Breeding season. Illinois Audubon Bulletin 187:27-35. . 1979a. Field notes. Spring migration. Illinois Audubon Bulletin 190:23-35. 1979b. Middlewestern prairie region. American Birds 33(2):181-185. .1979c. Field notes. Fall migration. Illinois Audubon Bulletin 188:39-52. . 1979-1980. Field notes. Breeding season. Illinois Audubon Bulletin 191:25-34. . 1980a. Field notes. Fall migration. Illinois Audubon Bulletin 192:24—36. 1980b. Middlewestern prairie region. American Birds 34(2): 166-169. . 1980-1981. Field notes. Breeding season. Illinois Audubon Bulletin 195:34—-47. . 1981la. Field notes. Fall migration. Illinois Audubon Bulleun 196:36-52. . 198lb. Field notes. Spring migration. Illinois Audubon Bulletin 198:36-57. . 1982. Field notes. Fall migration, Illinois Audubon Bulletin 200:38-58. . 1982-1983. Field notes. Breeding season. Illinois Audubon Bulletin 203:25-39. . 1983. Field notes. Winter season. Illinois Audubon Bulletin 205:42-49. , and L. Busn. 1972. Middlewestern prairie region, American Birds 26(1):70-73. Lawrence, L. peK. 1953. Nesting life and behavior of the red-eyed vireo. Canadian Field- Naturalist 67(2):47-77. 38 ILLINOIS NATURAL HistoRY SURVEY BIOLOGICAL NOTES Lewis, G.P. 1923. Chicago region. Bird-Lore 25(6):401402. LINKLETTER, J. 1975. 105. Disturbed mixed prairie. American Birds 29(6):1121—-1122. . 1977. 93. Disturbed mixed prairie. American Birds 31(1):63-64. ,and F. Woo-ey. 1978. 82. Disturbed mixed prairie. American Birds 32(1):81. MayFIELp, H. 1961. Nesting success calculated from exposure. Wilson Bulletin 73(3):255-261. . 1975. Suggestions for calculating nest success. Wilson Bul- letin 87(4):456-466. McKinney, N. 1966. Illinois nesting records—1965. Audubon Bul- leun 138:13-20. Morrison, M.D. 1978. 39. Upland deciduous forest. American Birds 32(1):66-67. , and B. Pererjoun. 1977. 42. Upland deciduous forest. Amer- ican Birds 31(1):44. Mumeorp, R.E. 1959a. Middlewestern prairie region. Audubon Field Notes 13(1):33-37. _______. 1959b. Middlewestern prairie region. Audubon Field Notes 13(5):433-434. Munort, A.H. 1883. Oological and ornithological. Ornithologist and Oologist 8(2):9-10. MusseLMan, T.E. 1913. A comparative study of bird migration in Illinois along the 40th parallel of latitude. M.A. Thesis. Uni- versity of Illinois. 74 p. . 1937. 1936 nature diary. Audubon Bulletin 27:36-4. Netson, E.W. 1877. Notes upon birds observed in southern Illinois between July 17 and September 4, 1875. Essex Insutute Bulleun 9:32—-65. Nice, M. M. 1950. Red-eyed vireos in Jackson Park. Audubon Bulletin io alGats . 1952. Breeding birds of Jackson Park. Audubon Bulletin 82:3-7. Nolan, V. 1958. Middlewestern prairie region. Audubon Field Notes 12(5):415-417. . 1960. Breeding behavior of the Bell vireo in southern Indi- ana. Condor 62(4):225-244. ,and D.P. WootprincE. 1962. Food habits and feeding behavior of the white-eyed vireo. Wilson Bulletin 74(1):68-73. Peattie, D.C. 1938. Spring song at the grove. Chicago Naturalist 1(1):3-9. PETERJOHN, B.C. 1981. Middlewestern prairie region. American Birds 35(5):828-832. Pirerka, F.A. 1941. Distribution of birds in relation to major biouc communiues. American Midland Naturalist 25(1):113-137. ,and E.J. Korstner. 1942. Breeding behavior of Bell's vireo in Illinois. Wilson Bulletin 54(2):97—106. Pouinc, O.C. 1889. A list of birds in whose nests the cowbird’s eggs have been found. Ornithologist and Oologist 14(9):133-134. Reep, C.A. 1965. North American birds eggs. Revised ed. Dover Pub- lications, Inc., New York. 372 p. Rice, L.A. 1946. Studies on deciduous forest animal populations dur- ing a two-year period with differences in rainfall. American Mid- land Naturalist 35(1):153-171. Ripeway, J.E. 1923. Olney. Audubon Bulletin, Spring: 32-36. RipGway, R. 1871. New birds in southern Illinois. American Natu- ralist 6(7):430-431. . 1873. The prairie of southern Illinois. American Naturalist 7(4):197-203. . 1874. The lower Wabash valley, considered in its relation to faunal districts of the eastern region of North America. Boston Society of Natural History Proceedings 16:304—332. . 1887. List of birds found breeding within corporate limits of Mt. Carmel, Illinois. Ridgway Ornithological Club Bulletin 2:26-35. 1889. The ornithology of Illinois. Vol. 1. Illinois State Laboratory of Natural History. Reprinted 1913. Pantagraph Printing and Stationery Company, Bloomington, IL. 520 p. & 32 plates. _____. 1904. Birds of North and Middle America. U.S. National Museum Bulletin 50, part 3. 801 p. No. 124 . 1915a. Bird-life in southern Illinois. II]. Larchmound: A naturalist’s diary. Bird-Lore 17(2):91—103. . 1915b. Bird life in southern Illinois. 1V. Changes which have taken place in half a century. Bird-Lore 17(3):191—198. . 1923. Illinois prairies in 1871. Audubon Bulletin, Fall: 51-54. 1925a. Spring notes at Larchmound. Audubon Bulletin 16:22—23. . 1925b. The birds of Larchmound—a resumé. Bird-Lore 27(5):305-309. Roserts, G. 1923. An Illinois yard. Bird-Lore 25(6):392. RosertTson, W. 1941. 33. Cut-over upland forest with pond. Audubon Magazine 43(5):496—-497. Audubon Magazine 44(5):27 (supplement). . 1944, 14. Upland oak-hickory forest with pond. Audubon Magazine 46(5):19 (supplement). ,and D. Snyper. 1948. 1]. Cut-over upland oak-hickory forest. Audubon Field Notes 2(6):233. RuEGNITz, R. 1952. Bell’s vireo nesting at Dubuque. Iowa Bird Life 22(2):30. Sanporn, C.C. 1921. Chicago region. Bird-Lore 23(5):251-252. . 1922. Recent notes from an old collecting ground in north- eastern Illinois. Auk 39(3):367-373. , and W.A. Goetitz. 1915. A two-year nesting record in Lake County, Illinois. Wilson Bulletin 27(4):434-448. ScHaFER, J.J. 1917-1918. The fall migration. Audubon Bulletin, Win- ter: 40-43. . 1923. Notes from Port Byron. Audubon Bulleun, Fall: 37. ScHANTz, O.M. 1931. Backyard notes. Chicago Academy of Science Program of Activites 2(1): n.p. Seets, J.W., and H.D. BoHLEN. 1977. Comparative mortality of birds at television towers in central Illinois. Wilson Bulletin 89(3):422-433. SEGAL, S. 1960. Bird tragedy at the dunes. Indiana Audubon Quarterly 38(2):23-25. Sittoway, P.M. 1894a. Bell’s vireo. Oologist 11(7):234-236. _____. 1894b. The study of bird life. Oologist 11(11):319-327. _______. 1906. A novice’s note-book—No. 4. Oologist 23(6):89-91. . 1913. Random notes in review. Oologist 30(4):70-72. Situ, E.T. 1941. Chicago region. Audubon Magazine 43(4):392-393. . 1942. Chicago region. Audubon Magazine 44(4):8-9 (sup- plement). ,and P.A. Du Mont. 1944a. Middlewestern region. Audubon Magazine 46(4):104—106 (supplement). , and . 1944b. Middlewestern region. Audubon Mag- azine 46(5):6-8 (supplement). Snyper, D., C. BONNEY, and W.B. RoBerTSON. 1948. 15. Deciduous floodplain forest. Audubon Field Notes 2(6):237. Stine, P. 1949. 28. Shrubby field and forest edge. Audubon Field Notes 3(6):271. STRUMBERG, C.W. 1879. (Untitled note.) Ornithologist and Oologist 4(12):95. Swink, F. 1976. A finding list of the birds of the Morton Arboretum. Revised ed. Morton Arboretum Booklet 1. 43 p. Tuompson, M.D. 1958. The 1959 breeding bird census. Audubon Bul- leun 108:5-11. Twomey, A.C. 1945. The bird population of an elm-maple forest with special reference to aspection, territorialism and coactions. Eco- logical Monographs 15(2):174-205. Vestat, A.G. 1960. Forests at the ime of settlement. Forest, wildlife, and recreational resources. Atlas of Illinois resources. Section 3. Illinois Department of Registration and Education, Springfield. 48 p. Wipmann, O. 1907. A preliminary catalog of the birds of Missouri. Academy of Science of St. Louis Transactions 17(1):1-288. WILHELM, G. 1954. St. Louis area 1953. Bluebird 21(5): n.p. Witson, B.H. 1906. The birds of Scott County, Iowa. Wilson Bulleun 18(1):1-11. Wooprurr, F.M. 1907. The birds of the Chicago area. Chicago Academy of Sciences Natural History Survey Bulletin 6. 221 p. ZIMMERMAN, J., and P. STEFFEN. 1975. Rosehill cemetery, Chicago. Page 21 in E. Fawks and P.H. Lobik, eds., Bird finding in TIli- nois. Illinois Audubon Society, Downers Grove, IL. MANUSCRIPTS WANTED High quality manuscripts dealing with any aspect of natural history will be considered for publication in one of the Illinois Natural History Survey publication series: Bulletin, Biological Notes, Cir- cular, and Special Publication. The author need not be an employee of the Survey, but if not, will be required to pay printing costs. Manuscripts must follow the recommendations of the third edition of the Council of Biology Editors Style Manual except that journal names in the Literature Cited section are to be spelled out in full, The survey expects to publish only one or two manuscripts by non-Survey authors yearly. Please send three copies of manuscripts to be considered for publication to Office of the Chief, Illinois Natural History Survey, 607 East Peabody Drive, Champaign, Illinois 61820. Printed by Authority State of Hhinois US ISSN 0073—490X 8 85-3M-Order No. 48314 mir ar potas Path els Nettie , ‘ : Been ahr g yell an fats : 7 ty ARE Se nad ioesd < ae , e eda att FE ou ‘ ) ANP HT Weiser : Z é ; Ti ea Win re pepe ts hey ute ed? eg ae Sh a Danae Sen dagen eee yon tes , eniei ah Saeegy Gi wi f : oak SDR tent ae se, Loney, Pearse ais PCO LLY AM Aire sey ERAS eae ry Iiatepialghry EA Ma Naber Sorte St es 4 wale bf ¥ arin hie a fe ‘ pda chet te Por ’ ee i atabpatenis ge Tate, athe ts By fae length Kine fee WW p Reh Vent inet be s y we i Ve DE pe RAO gy Cretan iy ip a Ws data iM Acaiy Latte: ete oT el t 7 yd ve ab ae Peete be in ya! y aepoge CONES Oey Ets Maegan pov: ae} Breer oie: penne tobe Veh ea Woon > Pate ARP Te Fite wi che fh a : ’ ADE ae Ay Pat I ie a ees Dy ted tea S a. Sa sintedepeweb, Vysferier 2 Ms 4 iow hit rade FAY, 1s Bs RNa aorh we ha tyes Dob phe SCSI thee ee date FRET 1 PLE Oe Pale ieke Vib aGas vas i) tae et eee rer Tai pe eiebe oa tin Cen eri tre ee FEE ae oe a Ro EET eas Fl 24 Sd 4 ie are Clr eh Beer ie ms aa . AO BY Ne od oD op WOMANS 4am Ned re 8 oat, PA BS Metpact oh wie ashe Bt ee ein ded ee Tse goa Dive ye . A ytne been 8) ° oe Venda r rau a Ke pease hecoerwe a ce Ze é ae ese Phere Wiest aren Sot BAA a Kk BA Tn be POT AATE Me ISSN Sp ‘ aout Fat Pe YD rae aro ra Ae Dee D AEN" ake APIS SPY eda dees ate NS ono ay Lm ASE apy krpess ¢ f Ak Pa avn mes daly pat cer, 4 bbe yee Se IS, os i SLATS aU ii Setaise cine Se PI Aa Se Ae tLe rou sven STE s Sir mee Sohn eT ae tee % ‘ r naa Se funte three tinea ie py tertenr AAA NAS hE Nie fC ARE! eT ES) BP iced POP Aer a geN ANE N > Eee rot Ad OP we Hl 9 RAV AT eT Mosh iak a ie Synainaet PAA EES Une SLD aS SS HFN PN tM nF PUNE Oe ym ne ee Fey eae Drewes bay) Fah Sled wy x Peek AA Pee poe aT SEO r> ey ae PARSE iy oh Sh Howe heen Maren Pye & ton © Rtetres sts ee gee yah Rae ks CARN ep Speers ws . Peters SNES te, eae meen a ay ean pasta Ane) ay fa Sh Oe. ‘ ; ies x ‘ iain aN eee naan \ weer: St td el het i ty nt tek me eae NEN EAT RTP ESS Rae De Wes es \ Sa LON A AD Ue a * WF RRR eR ent “ 2; AAR teieaniay motouyeast tks ; Corea *e — yay Socata SSN SN ae orcas, SN ASSESS Reet Sane a Se sass =< " ‘ \, ‘ ‘ i beat ee Y SANS NN NS ails tS Manse hres aes Ss Suc bree ¥ ya Ny St he ange ee a Y + VA es Shae 5 wy ia Ack * * my Mh ‘ CM MY San AeA hb Vail ‘ “ x ‘ a SASES : Aire ARAMA Ra NOM SAE - ‘ 4 ‘a a AS rs Ss Nahebes 89 Nae : nye an RSE ‘5 . x Nei Dyan Ny § : rh Mahe ‘ RAS it WAS i : Weihe bobs = A v ie Ra ; . 5 U Pan Prete tt Nh . ; Sh