0 20 30 APR 10 20 30 9 MAY JUN JUL AUG JUL AUG SEP a CENTRAL OCT 20 30 9 19 29 10 20 30 10 20 SEP OCT SOUTH 20 30 9 19 29 10 20 30 10 20 JUL AUG SEP OCT ig.
14.—Ege-laying and migration seasons of the wood thrush in different regions of the state (see Fig.
1).
Spring and fall graph lines (1967-1970) ighest daily count of each 2 days.
The lines are interrupted where data have not been collected. Star symbols represent counts made in other years or er observers. Shaded areas show the span of dates of egg laying. Dot symbols represent counts made on the western side of the state; lines without present the eastern side.
Migration /ehaveseenwoodthrushesstillinmoltaslateasSepr20incentralIllinois,andspecimenskilledattelevilowers often show a few pin feathers in the body geinlateSeptember. hen silent, wood thrushes are difficult to find, and ilenceprobablyhasmuchtodowiththerelativelack records(Fig.14).Wehaverecordedonly1inthefall ery 15-20 in the spring. After the singing ends, in August,oneoccasionallyhearsthethrush’sdistinctive totes, but generally the species goes undetected. lativelyfewwoodthrushesarekilledatIllinoisteletowers.Inasampleofseveralthousandspecimens up in central Illinois, this species comprised only 0.5 percent. They have been killed in migration at earlyasSeptember12andaslateasOctober14. i’ censuses indicate that the migration is largely h by the end of September (Fig. 14). There are recr the wood thrush in northern Illinois in mid-No- "and late November (Fawks 1970, and Holcombe butthesemustbeconsideredaccidental.Awinter or southern Illinois (Harlow 1921) is of doubtful r = FoodHabits Forbes (1903) examined the stomach contents of 22 woodthrushestakenfromApriltoSeptember,probablyin central Illinois or central and northern Illinois. He found thatamongthethrushesandmimids,thewoodthrushwas near the top in the amount of insects taken (71 percent of the diet), and low in fruit consumption (19-21 percent). In thespring,thewoodthrushwasexceptionalintheamount ofmillipedsitconsumed(13percent),anditalsofedheavily on ants (15 percent). Coleoptera (18 percent of the diet) wereimportant,consistingmainlyofgroundbeetles,scarabs,clickbeetles,wireworms,andweevils.Forbesbelieved thewoodthrushconsumedfewerpredaceousbeetlesthan other thrushes. Flies, notably larvae of crane flies and Bibio, made up 12 percent of the food. Spiders and harvestmen made up about 1 percent of the diet, and molluscs about 1 percent. Rice’s data (1946) on food habits of the wood thrush are roughly comparable to Forbes’ data, thoughRiceindicatedlargernumbersofHemiptera(10-20 percent)inthedietthandidForbes(only1percent). InSeptemberwehaveseenwoodthrushesfeedingon thefruitofspicebush(Linderabenzoin),andpokeweed. lye
NESTS or YOUNG @ 1950- A1900-1949 @ BEFORE 1900 PAIRS or SINGING MALES (JUNE) 1 MERCER Ale WARREN | A 1900 - 1949 re O 1950— i ——al i ea scorT PIKE oul O B WOOD THRUSH BREEDING RECORDS on ie | ic ©) FULTO HELM ARS | Moc LEAN plaice tae e i Bis: “4) \ | pated eae Fig.
15.—Breeding records for the wood thrush in [linois. Singing male records are for June only. TAaBLe 3.—Breeding populations of wood thrushes in various Illinois habitats. HERMIT THRUSH (Catharus guttatus) (Fig.16and17) SpringMigration Thoughthehermitthrushhasbeenrecordedinw atlocalitiesthroughoutthestate,thewinterpopulati sogenerallythinthattheonsetofthespringmigratic lateMarchisconspicuous(Fig.18).Thehermitisthe: cold tolerant of the Catharus thrushes, and arriv; springnearlyamonthinadvanceoftheotherthreesp (Annan1962),passingthroughthestatebeforethe speciesreachpeakpopulations.Mostofthehermitti populationisnorthofIllinoisbytheendofApril,and are very few spring records later than May 12 ev northern Illinois (Fig. 18). The peak numbers of he probably occur in southern Illinois April 1-15, andi centralandnorthernregionsApril10-30. ThehermitisthequietestofthefourCatharusth es. Incontrast to the loud calls of the other specie hermit’snoteissoftandlow.Ourphoneticsforthecz “tock? “tuck,” or “trock,” and the call is not heard1 so often as the calls of the other species. We have) heardthehermit’scallfromnightmigrants,andoui indicators of the timing of migration are the few ht killedatnightontelevisiontowersinthefall.Wehav er heard a hermit thrush sing in Illinois, though tk sing occasionally in the northern region of the (Farwell1919,andCraigmile1945). Viewsastotheabundanceofthehermitthrush markedly. Nelson (1876-1877) noted that the speci Birds Per | Type of Region or Habitat Acres 100 Acres” Years Census County Reference Virgin bottomland forest VI 21 1948 Nest Sangamon (C) Snyder, et al. 1948 Bottomland forest 20 1966 Nest Vermilion (C) Karr 1968 12-24 1946-1951 Nest Piatt (C) Weise 1951 Upland forest Le 6-10 1946-1951 Nest Piatt (C) Weise 1951 Forest edge 60 0-2 1959-1962 Nest Piatt (C) Balda 1963 Oak-maple forest 5s) 0-14 1927-1948 Nest Champaign (C) Kendeigh 1944, 1948 55 0-10 1949-1970 Champaign (C) Kendeigh & Brooks 196: Barnett & Balda 1966 — 64 12 1943 Nest Champaign (C) Johnston 1947 | Upland oak-hickory forest 24 5 1967 Nest Hancock (C) Franks & Martin 1967 Forest (all types including edge) 79-98 1 1957-1958 Strip North Graber & Graber 1963 | 97-117 0-1 Central 166-174 3-6 South | Second growth or cut-over woods 1S 40-93 1937-1938 Nest Rock Island (N) Fawks 1937, 1938 | Late shrub at 14 1966 Nest Vermilion (C) Karr 1968 Shrub areas 62-67 3-6 1957-1958 Strip South Graber & Graber 1963 Grazed bottomland 93 1 1955 Nest Macon (C) Chaniot & Kirby 1953 | Swamp and thicket 13 2 1950 Nest Jackson (S) Brewer & Hardy 1950 Urban residential 98 2 1958 Strip South Graber & Graber 1963 4 All figures were converted to read birds per 106 acres (number of territorial males or nests x On 18
y abundant in northeastern Illinois, and Nehrling 80) found it not very common inthe north. Judging nthecountsofotherobservers(Annan1962,Eiseman shank 1962, Clark & Nice 1950, and Labahn 1941), mitthrushesappeartobemorecommonalongthelake in northeastern Illinois than in any other section of the state.Alargekillofhermitthrushesbyastormatthesouth end of Lake Michigan on April 16, 1960 (Segal 1960) also tendstosupporttheviewthathermitthrushesbecomeconcentrated at the lake. We found the hermit thrush least - 16.—Hermit thrush, generally the most heavily spotted of the Illinois Catharus thrushes. (It also has a conspicuously reddish tail.)
commoninsouthernIllinois,possiblybecauseofthelarge amount of concealing cover.
FallMigration Afterthespringmigrationhermitthrushesaregenerally not seen in Illinois again until mid-September or late September (Fig. 18). Though there are a few August records(Ford1956),weareinclinedtodiscountthemeitheras accidentalrecordsormisidentifications.Mostofthehermit thrushes pass through Illinois in October, and nearly all aregonebyNovember15.Bennett(1952)hasshownthat thestrongOctobercoldfrontsoftenbringlargenumbersof hermits to the lakeshore of northeastern Illinois (see also Jung 1925). The largest numbers are seen on the first two daysafterthecoldfrontpasses.Asinthespring,thenumbers of hermit thrushes are low in southern Illinois (Fig. 18).
i)(=) Fig.
17.—General distribution of the | thrush.
ThoughtheotherspeciesofCatharusthrushesar quentlykilledattelevisiontowers,hermitsescapewitl fewcasualties,about.02percentofthethousandsof wehaveobservedastowervictims.
Recoveriesofhermitthrushesbandedinnortheé Illinois during fall passage (Fig. 19) have been Ww spread in the Gulf States (Bartel 1935, Downing | Jurica et al. 1959). Reuss (1953) recorded an indi\ hermitthrushstayingaslongas2weeksinthesamea northeasternIllinoisduringOctober. WinterRecords Therearescatteredwinterrecordsofthehermitt forallsectionsofthestate(Fig.20),buttherearenoF measurements of winter populations. Our own Ce (Graber&Graber1963)showedmeasurablepopul onlyoneyearoutoftwo,andthenonlyinthesouth,|
20 19 10 20 30 9 19 29 9 MAR APR HM CENTRAL 20 20 19 19 20 30 10 20 30 9 19 MAY SEP OCT NOV ig- 18.—Migration seasons of the hermit thrush in different areas of the state (see Fig.
1).
Spring and fall graph lines (1967-1970) show the highest ount of each 2 days. Star symbols represent counts made in other years or by other observers. Dot symbols represent counts made in west-central I]lines without dots represent the east. Dashed graph line (north) represents the cumulative counts of birds made by Benjamin T.
Gault between nd 1927 mainly in Du Page County, and shows the long-term peaks and range of migration dates. undonetotwohermitthrushesper100acresinforest hrub areas. The Christmas counts also show great l variation in the hermit thrush population (Fig. 21). neyearsmorehermitshavebeenfoundinnorthern isthaninthesouthernregion,butsuchrecordswere blymoreareflectiononthedistributionofobservers listributionofthebirds.Cooke(1885)reportedhigh ’populations(5-20hermitsseenperday)inthickets theMississippiRiver,butnorecentobserverhasreccomparablenumbers.Ina3-daycensusatGrafton, 1940)foundonlytwohermitthrushes.Bartel(1954) ed three in a day near Lisle (January 17, 1954), ina hentheChristmascountsindicatedhighpopulations south (Fig. 21).
itler(1896)suggestedthathermitthrushessufferthe ypeofcoldmortalityinthewinterandspringthatis ableinbluebirdpopulations,andJames’(1961)studies support this view. The low populations in 1958, 1959, and1960probablyrefllectsuchmortality. FoodHabits Inhisstudies,Forbes(1903)examined21specimensof hermit thrushes, which were nearly all taken in the spring in northeastern Illinois. Even for a thrush, the amount of insects eaten by hermits was high (84 percent of all food). Coleoptera(29-30percent)wereofmajorimportance,especiallypredaceousgroundbeetles.Forbesnotedthatthe spring migration of the hermit thrush is timed with the emergence of many beetles. Gault (1884-1889, unpublished notes) also found beetles to be the principal food. Lepidoptera (18-19 percent), and ants (13-15 percent) formed much of the rest of the diet. Like the wood thrush, hermits ate more millipeds (12 percent) than most birds. 21
HERMIT THRUSH WINTER RECORDS | DEC.1—JAN.31 a Rinne | ® 1950 a oe rome g ye | = CARROLL i aan ek Pr A 1900- 1949 Seal ae * | WHITESIQ PE ee:
| = Nl te =e ENDALL © ock BUREAU HENRY LA SALI EF wie oar GRUNDY ERCER ie UNAM! STARK wat MARSHALL 7 KN OK LIVINGST P £0 Rt A/™ wooor ORO {an Rae ae fice |. wn dsl BROWN CASS bret Se WH MaACQA a aad morgan {| SAN al DOUGLAS PLRKE ea > OULTREL = l = CHRISTIAN COLES al toe | SHELBY { ime GREENE pd puscousin MONTGOMERY 'UMBERLAND| | = EFFINGH v FAYETTE JASPER | Lt:
| y Fig.
19.—Winter and early spring recoveries of hermit thrushes banded in northeastern Illinois during fall migration. Grasshoppers (7-8 percent), Hemiptera (7-8 percent), and vere | spiders (4 percent) made up most of the remainder. wae. ! Forbes found no fruit in the diet, but he examined only ek ; ee ao two fall specimens. We have found hermit thrushes to be ae ee a | very found of pokeberries, and have also seen them feeding . | onwildgrapesinOctober.NothinghasbeenrecordedonFig.20.—WinterrecordsforthehermitthrushinIllinois.T) the winter food. regions of the state discussed in the text are shown by heavy lines. | NORTH —— CENTRAL—-—— SOUTH —— Fig.
21.—Annual variation in winter hermit thrush populations, based on Audubon Christmas counts in three regions of the state. Graph linesshowthenumberofhermit thrushes seen per 100 party hours. (For information about the Audubon Christmas counts, see Cruickshank 1970.) BIRDS per 100 PARTY HOURS w 1940 1950 1960 22
JAINSON’S THRUSH (Catharus ustulatus) (Fig.22and23) ‘ing Migration Swainson’s thrushes generally begin to appear in IIlisinsmallnumbersaboutApril20,withnotmorethana *k to 10 days difference in arrival between south and th (Fig. 24). Though there are records for the north as ly as March 31 and early April (Ford 1956 and Abbott |.1933)wesuspectthatthesearebasedonmisidentitions of hermit thrushes. Most Swainson’s thrushes s through Illinois during May, with peak populations sing the south in early and mid-May and the central | north in mid-May and late May (Fig. 24). A few inson’sthrushesregularlylingerincentralandnorth- IllinoisthroughthefirstweekinJune.
Themigrationsareprobablystrictlynocturnal,somes lasting all night (Cochran et al. 1967, and Kjos & hran1970).Themigrationsareoftenaudiblebecause he birds’ loud calls, which are uttered during the day .. We translate the calls most frequently given as eek” and “whit.” More rarely the calls sound like §.
22.—Swainson’s thrush.
(The thrush with buffy ‘“‘spectacles.’’) “sweeur”’or“‘peeur,”’whicharemuchmorecharacteristic ofgray-cheekedthrushesandveeries.Swainson’sthrushes arealsostrongsingersduringmigration.
WesawthelargestnumbersofSwainson’sthrushesin east-central Illinois, and the fewest in the south (Fig. 24). The pattern of high populations in the east is, in our experience,consistentfromyeartoyear.Therearenoabsolute measurementsofmigrantthrushpopulationsforanylocalityinIllinois,norhasanyoneattemptedaprecisedefinition of thrush habitat. We see them in a wide variety of woody habitats.
FallMigration There are a few July records for the Swainson’s thrush in northern Illinois (Nelson 1876-1877, Ford 1956, and Eiseman & Shank 1962), but generally the first indication of the fall migration comes in mid-August or late August (Fig. 24). At Glen Ellyn, Gault (unpublished notes 1884-1915) fairly regularly detected the first fall Swainson’sthrushesaroundAugust20.Onespecimenhecollected on August 21, 1895 was in heavy molt. The first birds to ZS
+ miles reach southern Illinois in the fall are almost 2 weeks later, inearlySeptember(Fig.24).
Most of the Swainson’s thrush population passes through Illinois in September, with peak numbers in the north probably in early September, and incentral and southern Illinois in mid-September to late September. Smallnumbersarefounduntilmid-Octoberthroughoutthe state. A few may linger into November (Ford 1956), but winter records (Ford 1956, Ridgway 1889, and Norton & Spitzer1965)areaccidentalorerroneous. During‘theirnightmigrations,Swainson’sthrushesare amongthemostcommoncasualtiesattelevisiontowers. Thereisgoodcorrelationofdatesbetweenourhighestcensus counts and the highest kills in central Illinois (Fig? 24 and 25). As in the spring, the lowest counts of Swainson’s thrushes in the fall were in the south. The tower kill data for Cape Girardeau, Missouri on the Mississippi River alsoindicatethatfewerthrushesmigratethroughsouthern 24 Fig.
23.—General distribution of the S son’s thrush.
Illinois.PaulHeye(mimeographedreport)foundthe temberkillsofmigrantstheretobegenerallylower thoseincentralIllinois,andthepercentageofthrust bemuchlower(1percent,versus14percentincentra nois).
Inourcensuses,thefallcountsofSwainson’sand Catharusthrusheswereconsistentlymuchbelowtho spring. This is contradictory to expectations, and a thefindingsofAnnan(1962)whoseeraphsfornortl ernIllinoisjustasconsistentlyshowmuchhigherpo tions in the fall. His data show a ratio of 1 bird 1 spring to 11 inthe fall, versus our counts for then which show 4 birds in the spring to 1 in the fall. Thi seriousdiscrepancycannotberesolvedwithoutbette sus methods. .
Ourcensusesshowedthesamespringtofallratic 1) of Swainson’s thrushes for east-central I}lino! northernIllinois,butverydifferentratiosforwest-¢