29 10 20 30 9 19 29 MAY 15 JUN 20 10 20 3 9 APR MAY 19 JUN - 31.—Migration seasons of the veery in different areas of the state ( CENTRAL 29 10 20 30 9 19 29 o 19 29 1052 Ome 9 Lo ene 29 JUL AUG SEP see Fig. 1).
Spring and fall graph lines (1967-1970) show the highest daily each 2 days. Star symbols represent counts made in other years or by other observers. Dot symbols represent counts made in west-central Illinois; hout dots represent the east. Dashed graph line (north) represents the cumulative counts of birds made by Benjamin T.
Gault between 1875 and inly in Du Page County, and shows the long-term peaks and range of migration dates. heek and Swainson’s thrushes. Most of the veery tion is through Illinois by September 20. There are Jctoberrecords,thelatestbeingOctober13forthe Ford1956),andourspecimenfromacentralIllinois ontower,killedthenightofOctober8-9,1968. withthegray-cheekedthrush,wesawfewveeriesin in comparison with spring (Fig. 31). This was also Derience of William Dreuth (Clark & Nice 1950), njaminGault(Fig.31).InnorthernandcentralIIli- "Saw6~7veeriesinthespringtoevery1inthefall, hesouththeratiowasabout20boul: Ties are less common than Swainson’s and gray- IthrushesinIllinois,andthispopulationdifference ctedinthetowerkills(Graber1968).Onlyabout1 ofthebirdskilledatcentralIllinoistelevisiontoweptember were veeries. SpecimenData We have examined 41 fall and 34 spring specimens of veeries from Illinois, but no Illinois breeding specimens. Amongthemigrantstherearetwocolorextremes,redand grayish, with virtually complete color intergradation and no consistent size difference between the two. The gray specimens well match even the extreme gray specimens fromtherangeofthewesternraceCatharusfuscescenssalicicola,andtheredspecimensaresimilartospecimensfrom therangeoftheeasternraceC.f.fuscescens.Therearefew specimensoftheeasternracefromIllinois,whilesalicicola is well represented. In the fall probably all specimens are best ascribed to salicicola, with about 5 percent showing intermediacytowardsfuscescens.Inthespringmostofthe birds are salicicola, but about one-third are of the eastern form. 33
VEERY BREEDING RECORDS NESTSorYOUNG @ 1950- A1900-1949 @ BEFORE 1900 PAIRS or SINGING MALES (JUNE) O BEFORE 1900 LIVIN IN H Se ae i —— iROQUOIS | ail al L__4 | FULTON MAZE We | Me LEAN Foro L_ rial eee ene a aaa os ) wl MASON 2 j vt AN|pyBoe D A1900-1949 O 1950— 7 i GREEN! j i ie est|aliirf-FumeenLsvoCLARK Me | | EFFINGHAM e ~ Se a ve Ra | pee? |cnawrond J. ie a Fig.
32.—Breeding records for the veery in Illinois.
Singing male records are for June only.
EASTERN BLUEBIRD (Sialia sialis) (Fig.33and34) Spring Migration Thoughtherearewinterrecordsofthebluebirdforall regionsofthestate,andthereisasizablewinterpopulation vn southern Illinois, the migrations are conspicuous (Fig. 35). The arrival dates most often given are around February 20 for central Illinois and February 26 for the north. Arrivals in early February are apparently infrequent in both regions, but in some years bluebirds are common in central Illinois even in January (Musselman 19395 1934-1935, and 1939), with groups of 30 or more being seen.
The largest numbers of bluebirds in the spring have beenrecordedinMarch,andmostofthemigrationprobably occurs in that month (Fig. 35). Zimmer (1922) observed “hundreds” near Rock Island on February 22, but notedthatsuchaggregationswereunusual.Populationsin 34 thespring,aswellasinotherseasons,arehighestins¢ ern Illinois.
Judgingfromtheliterature,theactualmigrationfl arerarelywitnessed.VanDuzer(1922)andSchafer(l recordeddiurnalflights,possiblymigrations,innort Illinois in late February and in March. We have definite diurnal migrations of bluebirds only in the (Fig.35).Thereisnoevidenceofnocturnalmigration, asnightcallsandtelevisiontowerkills,asthereisfor| thrushes.
Distribution The general distribution of the bluebird is shoy Fig. 34. The available breeding records for Illinois 36)donottrulyindicatethestatedistribution.Large inthestate,especiallyintensivelycultivatedtracts,a sentiallydevoidofbluebirds.Weestimatedthat80pe oftheIllinoisbluebirdpopulationwasinthesouthern ofthestate(Graber&Graber1963). Nesting Habitats and Populations Thebluebird’susualhabitatincludeswoodyvege in or adjacent to open fields, especially grasslands. treelessareas,evenwherenestingboxeshavebeenp ed, are unlikely to have significant bluebird populz Largeblocksofforestarealsopoorforthespecies(\ 1964),thoughforestedgesupportslowpopulation (Table 6). Residential habitat was more important bluebirdpriorto1900,butthespecieshasbeendis by house sparrows and wrens (Nehrling 1880, Ri Lot Theearliestsuccessionalstagesofforestarenots! for bluebirds (Brewer 1958, and Karr 1968). In so Illinois Brewer found no bluebirds in strip-mined that had been abandoned about 14 years. | Bluebirdhabitatsmusthavesuitablenesting¢i andtheeliminationofrailfencesandwoodenfenc has had a detrimental effect on the bluebird pop (Musselman1940).Bluebirdsseemtohaveunderge transitions with regard to nesting sites in the pz years. Many of the early references (before 1900) nestsincavitiesofdeadtrees,stumps,orthedeadbr ofcottonwoods(Populus),willows(Salix),ororchal (Gault, unpublished notes, 1876-1889; and Loue publishednotes,1888).Fromdeadtreestofencepo 4naturaltransition,andmostofthenestsrecordec literaturewereinfencepostsuntilrecentyears,©] since1950,whenmostoftherecordshavebeenfre boxes.BluebirdnestingboxroutesliketHtoseestabli Musselman (1944), and Varner (1964) are now Pp importanttothespecies.Therearenodataonthe bilityofnaturalcavities. Bluebirdnestsinnaturalcavitieshavebeenrece lowas1%feetabovegroundandashighas11feet haveundoubtedlybeenmuchhighernests,butm ords,evenfornaturalsites,arebelow7feet. Theonlyterritorymeasurementwehaveseen
33.—Bluebird carrying food near 1 in Illinois is that of Fawver (19472), 3.5 acres. man(1935)notedthatbluebirdsdidnotnestcloser ‘than one-fourth of a mile in west-central Illinois, tel (Smith & DuMont 1944) effected a 40 percent InabluebirdpopulationnearBlueIslandwhenhe dthenumberofnestboxesfrom10to27inaone- ©squarearea.Inthesouthwehavefoundcontemusnestsasclosetogetheras380feet. a nest box, in Pope County, Illinois.
Majorperiodiccrashesinthebluebirdpopulation(Fig. 37)isaphenomenonoflongstanding.Butler(1896)noted a sharp decline in northern Illinois and Indiana in 1895 and attributed it to severe cold in April. Later studies have alsoindicatedthatsuchcrashesare,toalargedegree,correlatedwithadverseweather,especiallyinthewinterand spring (Barnes 1912, Musselman 1941, and James 1960). Musselman(19412)estimatedthat50percentoftheblueoo
° 200 400 600 800 miles birdpopulationinwest-centralIllinoissuccumbedtocold and snow one spring. In ‘Tennessee, which is part of the bluebird’s winter range, Laskey (1958) found many dead bluebirdsthathadbeenroostinginnestboxes(asmanyas 12deadinonebox)afterseverecoldandsnowinmid-February.Wehavealsofounddeadbluebirdsinroostingcavities in February in southern Illinois, and Musselman (Peterson1965)founddeadbirdsinhisnestboxesinApril. NestingCycle Banding returns reported by Bartel (1950, 1952), Holcombe (1930, 1932), and Musselman (1934) show that someyoungbluebirdsaswellasadultsreturntotheareas oftheirbirthandtheadultssometimesreturntothesame box.However,noquantitativedatahavebeenpublishedto show what part of the population returns. Musselman (1934)feltthatyoungbirdstendedtoscattermore. 36 Fig.
34.—General distribution of the bluebird.
Thereislittlereferencetothebluebird’ssongint noisliterature,andnearlyeverymentionoftheson; to the month of March as the time of singing. Ri (1889) indicated that there was a resurgence of s songinAugust,buttheperiodicityofsinginghasn recordedinanysystematicway.
The earliest nest with eggs for Illinois was 1 March 20 by Musselman (1937) in central Illinois isnoindicationthatnestingbeginsearlierinthesou 35).Thelayingcurvesforthebluebirdhavesevera The first peak occurs in April throughout the stat about a 12-day lag in the north (Fig. 35). There : laying peaks in May and June, and though a few 0 establishedaslateasmid-August,laying1slargely theendofJune.
Musselman’s work with banded birds show bluebirdstendtohavetwobroodsinoneseason. pairofbluebirdsmayusethesameboxfortwocon
“HUNDREDS'' mm MIGRATING LEGG LAYING oe 724 °«412s«-24 1224 12 24 FEB MAR APR MAY JUN Wi AUG SEP © Gi NOV uJ ¥-50— » z (a) GENTARAL Zz. ud 2 O Zz O a < 12 24 12 24 FEB MAR APR MAY JUN JUL AUG SEP OCT NOV G MLC ALING st Oo iL O — Z Ww O [a4 lw EGG LAYING 5 o ae & SOU) Vial 4 3 ° 2 - @ e 1 12 24 12 24 1224 12 24 12m 12 24 FEB MAR APR MAY JUN JUL AUG SEP ONE jj NOV 35.—Egg-laying and migration seasons of the bluebird in different areas of the state (see Fig. 1). Spring and fall graph lines (1967-1970) show est daily count of each 4 days (left scale). The lines are interrupted where data have not been collected. Star symbols represent counts made in othor by other observers, mainly before 1930. Dot symbols represent counts made on the western side of the state; lines without dots represent the ide. Shaded areas show the percent of eggs laid on a given date (right scale). Arrow symbols indicate dates of actual migration flights. (Holcombe 1930), females also often change houses have apparently not been substantiated by observations of ‘N nestings, sometimes moving miles away banded birds. Iman 1946). Some boxes have four sets of eggs ina The April laying peaks are much higher than the subse- (DuMont & Smith 1945), but not necessarily from quent peaks (Fig. 35), and data on-nest-box occupancy ¢ pair. References to three broods by the same pair show the same trend. During several years and in different oF
NESTSorYOUNG @ 1950- A1900-1949 @ BEFORE 1900 PAIRS or SINGING MALES (JUNE) CO BEFORE 1900 A1900-1949 TAZEWELL Me LAN O 1950— BLUEBIRD BREEDING RECORDS Scale 10 0 10 20 30 _40_SOMiles Fig.
36.—Breeding records for the eastern bluebird in Illinois. Singing male records are for June only.
areasinwest-centralIllinois,occupancyofhousesby| birds fell about 23 percent between the first (April May) and second (June and July) nestings, with the tremesindifferentyearsbeingaslowas8percentar highas66percent(basedondatafromMusselman| 1936,andEvers1937).Bartel(DuMont1947)recorde exceptionallyhighrate(90percent)of“‘second-nest occupancy in 1947 at Blue Island. There are no com} tivedataforthesouth. Thebluebirdappearstohaveaprolongednesting ThefullcycleforonenestobservedincentralIllinois, nest-buildingtofledgingofyoung,required47days($ 1939), but this was an early nest, started April 5, anc building was slow (12 days). Nests have been buil days or less (Musselman 1934-1935, and Varner | Wehaverecordednest-buildingperiodsof6and7di southern and central Illinois, with incubation peric 13-15days(mostfrequently14days),andnestlingpe of 15-17 days (most often 16 days). Holcombe’s ( observationsinthenorthalsoindicatedanincubation od of 14 days, and nestling period of 16 days. Thus, cycle,includingegglayingforanestwithfiveeggsm expectedtotakeabout40days. Throughoutthestate,mostnestsreceive5eggsf firstnesting,butclutchsizedeclinesinlaternests,esf lyinthesouth(Table7).Amongthehundredsofne observedMusselman(1946a)oncerecordedaclutch| eneggs,andoncenineeggsinonenest,contributedt females. Theeggsaregenerallypaleblue,butsometimes andrarelyarebothtypesfoundinthesamenest.In] tensivestudiesinwest-centralIllinoisMusselman| 1946)foundabout5-6percentoftheeggstobewhite Tape 6.—Breeding populations of bluebirds in various I}linois habitats. Birds Per Type of Region or Habitat Acres 100Acres* Years Census County Reference Orchard 5 80 1936 Nest Lake (N) Beecher 1942 Edge shrubbery 9 34 heey Strip South Graber & Graber 1‘ Block shrub areas 67 | 1957 Strip South Graber & Graber I' Late shrub ie 10 1966 Nest Vermilion (C) Karr 1968 Thicket ie) 1 1950 Nest Jackson (S) Brewer & Hardy 19 Residential 8 PES 1916 Nest Richland (S) Cooke 1916 Parkland estate 100 £2 1915 Nest Cook (N) Eifrig 1915 Unmodified woods 2 15 1936 Nest Lake (N) Beecher 1942 Forest (all types including edge) 19 l 1957 Strip North Graber & Graber !' 174 Z South Forest edge 55 (0-2permile) 1927-1970 Nest Champaign (C) Kendeigh 1948, Kendeigh & Clemai Second growth or cut-over woods LS 13 1937-1938 Nest Rock Island (N) Fawks 1937, 1938 Grazed bottomland 93 4 1955 Nest Macon (C) Chaniot & Kirby 1° Pastureland 147 3 1957 Strip North Graber & Graber ! 54 2 Central ee, 8 South 4 All figures were converted to read birds per 100 acres or birds per mile of edge ( 38 number of territorial males or nests x 2).
90. / oN ig. 37.—Annual 70 on in nest box occuby bluebirds for sevyutes in central and rn Illinois.
Two cenlinois routes showed me population crash (0, and there was a ilsimilarityinthe tion trends in north- 1 central Illinois.
HOUSES 30 OCCUPANCY OF % 1935 ¢incidenceofcowbirdparasitismofbluebirdnestsis Musselman 1942). The rate was exceptionally high > species in 1945, 7 nests parasitized out of 268, or 3 percent (Musselman 1946).
lerearenoextensivedataonnestingsuccessforpopms in either the north or south. Duncan’s -1935)smallsampleofnestsinCookCountyindicatgingsuccessof50percentoftheeggs.Ourdatafor ith,representing51nests,showedfledgingsuccessof cent in April and May, and 54 percent for June to t eggs.
stingsuccessforthebluebirdseemstodependagreat nweatherfactors.Evers(1937),inwest-centralI]lioundfledgingsuccessofabout90percentoftheeggs firstnesting(AprilandMay),butsuccessofsecond 8wasdownto50percent.Heattributedthereduced to very high late-summer temperatures (114° F. in de).Ina7-yearperiodMusselman(1939a)recorded evereAprilfreezesthatfrozemanyeggs.Hehasrecestingsuccessratesaslowas38percentandashigh ercent of the eggs (Musselman 1935). In general, nestingswerelesssuccessfulthanthoseinApriland nfertility varied from 1 percent to 23 percent, with rage of 9 percent, and low hatchability was again BLE7.—Clutchsizesofbluebirdsindifferentregionsof Percent of Nests by Clutch Size Number of Average 6 5 4 3 Months Nests Clutch Eggs Eggs Eggs Eggs April-May 642 5.0 16 2 = 42 0 June-August 57° 4.4 2 oe 2o en .19 April-May 1694 4.9 Ly Sai 4 June-August 274 Al 3) 2 43 39 16 April-May 15 51 eee Ee: 0 June-August 18 4.2 A ot ay €s records from the literature where complete data were provided.
NORTH» CENTRAL——- 1945 1955 1965 correlated with severe heat (26 days over 100° F.) and drouth.
Otherfrequentlymentionedsourcesofnestmortality relatetocompetitionwithotherspeciesfornestingcavities. Hodges (1953) noted that bluebird populations on Credit Island near Rock Island declined coincidentally with an increaseofhousewrens(Troglodytesaedon)inthearea.In other areas of northern and central Illinois bluebirds also faredpoorlyincompetitionwithwrensforhousing(Bartel fide Smith & DuMont 1944, and Musselman 1946). Wrens occupied from 2 to about 7 percent of Musselman’s nest boxes,andperforatedasmanyas7percentofthebluebird €ggssomeseasons(Musselman1935).Whenthebluebird’s firstnestingwasdelayed,thepopulationwasthrownmore directly into competition with the generally later-nesting wren(Musselman1939). InextremesouthernIllinoiswehavenotobservedany interferencefromhousewrens,butwrenpopulationsare low there. In northwestern Illinois, on the other hand, ina sample of 33 nest boxes we found 76 percent occupied by wrensinJune,versusonly9percentoccupiedbybluebirds. In east-central Illinois, Campbell (1970, and personal communication)recorded9percentof23boxesoccupiedby wrens,versus35percentoccupiedbybluebirdsin1970,but in1971wrenstookovermostoftheboxes. Inhumanresidentialareas,bluebirdscannotcompete with house sparrows (Passer domesticus), and there is competition even in rural areas. In western Illinois house sparrows utilized more nest boxes than did wrens. From data provided by Musselman (1934, 1934a, 1935, and personalcommunication)wecalculatedtheincidenceofoccupancy for sparrows in rural areas to vary from 1 to 14 percent, with an average of 6 percent. For redheaded woodpeckers (Melanerpes erythrocephalus), tufted titmice (Parus bicolor), and black-capped chickadees (Parus atricapullus),theincidenceofoccupancyaveragedabout5percent each. Nest boxes in woods and forest edge are more likelytoattractchickadeesandtitmice(Musselman1935). In southern Illinois we found Carolina chickadees 2h)
(Parus carolinensis) occupying from about 10 to about 40 percentofthebluebirdboxes,withbluebirdsoccupying60 percentoftheboxes.Wewitnessednoaggressivecompetition. However, in northwestern Illinois Wilson (Hodges 1954)observedthatbluebirdsandblack-cappedchickadees werekeencompetitors.InthesameregionSchafer(1920) sawredheadedwoodpeckersdestroybluebirdnests,andwe haveseenonesuchincidentinthesouth. Eifrig(1937)suspectedthatstarlings(Sturnusvulgaris) wereimportantcompetitorsofthebluebird(seealsoSchafer 1932, and Musselman 1934a, 1942), but this competitioncanbeeliminatedonnestingboxroutesbyproperbox design and placement (Varner 1964). Varner also warned that boxes near water tend to be taken over by prothonotary warblers (Protonotaria citrea), and tree swallows (Iridoprocne bicolor). Bluebirds also have to compete for cavities with small mammals, notably deer mice (Peromyscus) and flying squirrels (Glaucomys volans), and with wasps (Musselman1934,1947). Thereislittleinformationonothercausesofnestloss. Musselman(1946)consideredlossfromsnakepredationto be small, but cautioned (1935, 1940) that boxes in brushy orweedyplacesareparticularlysusceptibletoblacksnake, shrike, and mouse predation. Personswhowishtoestablishbluebirdnest-boxroutes should read Musselman (1941, 1944), Varner (1964), and Kibler(1969)forvaluableinstructions. FallMigration Ourdataindicatethatmostofthefallmigrationoccurs fromSeptemberintoearlyNovemberincentralandsouthern Illinois (Fig. 35). Our earliest observation of actual migrationflightsinsouthernIllinoiswasSeptember17and thelatestwasNovember6,butboththesedatesprobably fallshortofthetrueextremes. In our experience, bluebird migration was never the massive steady flow of birds as in the case of robins, blue jays, and other diurnal migrants. Bluebirds flew inthe morninginsmall,looseflocksgoingsouthandsoutheast. Nelson (1876-1877) dated the fall migration in northeasternIllinoisfromSeptember12toOctober25,andthis closelycoincideswiththetimingofourhighcensusfigures forthenorth(Fig.-35).Schafer(1922)recordedexceptionally large migrations in the north in 1922 nearly every day inSeptemberandearlyOctober. The numbers of bluebirds seen in the fall (September intoNovember)consistentlyexceededthespring(February through May 10) counts throughout the state. The ratios were one bird in the spring to three in the fall for central Illinois, one to six in the south, and one to eight in the north.
There are very few published band recoveries to indicate destinations of migrating Illinois bluebirds. Birds bandedinthespringandsummerinnortheasternandwestcentral Illinois have been recovered in the winter from southeastern Texas to southern Louisiana and southern Georgia(Bent1949,andMusselmanLOST): 40 WinterRecords Bluebirdshavebeenfoundinallregionsofthesta the winter (Fig. 38), but 90 percent or more of the st winterpopulationisinthesouthernzone(Graber&| ber 1963, and Fig. 39). In about one-third of the y therearenobluebirdsrecordedinthenorthernandce Christmas counts (Fig. 39). They are most likely | foundalongmajorrivers,especiallyinthenorthernh: the state (Fig. 38). The species is usually found in s flocksof3-20birds. Thebluebird’spopulationcrashes,asdiscussed\ NestingHabitatsandPopulationsabove,showupcl intheChristmascounts(Fig.39),andthereisgood¢ lationintimebetweenthelowbreedingpopulations lowpopulationsinwinter(Fig.37and39). Ourcensusesshowedpasturesandothergrassl forestedge,andshrubareastobefavoredwinterha (Graber&Graber1963).Theonlyabsolutemeasure! of winter populations are by Shaw & Scherer (1960) Shaw et al. (1964), who censused a shrubby field ar southernIllinoisandfounddensitiesrangingfromless one bluebird per 100 acres to seven per 100 acres il year census period.
WINTER RECORDS DEC.1-JAN.31 ears ce e 1950 1h Jo oe iam aer 8 | McHENAY Tt sa pes A 1900- 1949 (a CARROLL | tt 2 al; Bs wns| bo W BEFORE 1900 bea [ Lo ete 1 € ae “<7 i wy ene Bee :
c@er PUTNAM! MARSHALL, Waren LIVINGSTON | vid 5 peer ie ‘a EAN ‘ 2 | “a mine. ee Dams S BRO case) Ue @ im ee - a a. Ss aaworcan|SANGAMS—T(pouste PIKE scorrh 5 OULTRIE —_—- + CHRISTIAN OLE TOT | eo ea! GREENE SS ae Ley ., macoupin | MONTGOMERY re | wes eee a LY MADISON 4 a 7 oar” mn CLAY Vance $ Pa giPEOpWOODFORD # BLUEBIRD « CLINTON = = ST. CLAIR WAYNE INGTON wy © WASHINGTON | son 3 41 i RAWDOLPH Pel 2 Gada d me) aac ny | SALINE OALLA 5 + eS AR = ais te AROMP < onnson » ts _— en 10.010 20/39) °40_SOMiles ge Ws, ea a a a v CR Fig.
38.—Winter records for the eastern bluebird in Iilir three regions of the state discussed in the text are shown by heavy