egistration and Education — _ HISTORY SURVEY DIVISION fp —— aa es _UNIVERSITYOFJLLINOIS” ‘ HAMP,
"aw, 1970 — ee a eae 2 ea Ce Fig. 1.—Routes travelled (1957-1970) to study breeding distribution of Illinois birds. The encircled areas were special study areas where daily censuses of migrants and nesting populations of birds were carried out, 1967-1970.
INOIS BIRDS: Turdidae a HIS IS THE SECOND of a series of papers intendedtosummarizetheavailabledataonthebirds inois.Theintroductiontotheentireworkwaspresent- 1 the first paper, entitled Illinois Birds: Mimidae ber et al. 1970), and the policies and procedures for erieswereoutlinedtherein.Thispaperdealswiththe hes,andhereweneedmentiononlyafewproblemsof pretationnotencounteredinthefamilycoveredbythe rT paper.
ur censuses from 1967 to 1970 inclusive were made lyinnonurbanhabitats,i.e.,theyrepresentthecounleawayfromtowns.Thus,oursummercountsforthe ,whichshowsastrongpreferenceforhumanresidenreas,areunrealisticallylow. |discussingtherobinwearealsoconfrontedwiththe emoflargeaggregationsofbirds.Ourcensusesofthe tion for each species are intended to show the numfbirdsintheirdiurnalorforagingdistributionamong habitats in the study areas we selected (Fig. 1). We interestedinthequantitativerelationshipbetween ntandbreedingpopulations.Weavoidedcensusing vicinity of roosts where birds from hundreds of =milesmaybeaggregatedinasmallarea.Atcertain is,robinsdoformmassiveroosts,andcountsmadein reascouldbeexpectedtodiffergreatlyfromourdaily es. Robins are also greatly aggregated during their ilmigrations,andingraphingourcountsofmigrants +)wehavesometimesshowntwocountsforagiven nerepresentingtheforagingdistributionofthepopuand the other the number of birds in active migra- "hus,forexample,ourmaximumcountofrobinsfor 1 in southern Illinois was only about 400 birds seen the day, but during the late afternoon migration 1,600birdsflewoverin1hour. oughwetendtobeconservativeaboutnomenclaturiges,webelievethatDilger’s(1956)reclassification ocichlamuchbetterrepresentstherelationshipsof rthern thrushes, and have, therefore, included the thrush, Swainson’s thrush, gray-cheeked thrush, ryunderthegenusCatharus. thepreparationofthispaper,wereceivedhelpfrom ersons.WewantespeciallytoacknowledgeW.Ear] yoftheNationalMuseumofCanada,forexamining ofourSwainson’sthrushesandadvisingontaxonroblemsinthisspecies,andDonaldF.Hoffmeister University of Illinois Natural History Museum for Paper is published by authority of the State of Illinois, IRS Ch.
127, Par.
's a contribution from the Section of Wildlife Research of the Illinois Natry Survey.
Dr.
Richard R.
Graber is a Wildlife Specialist at the Survey.
V.
Graber is a Research Assistant Professor of Animal Science at the Uni.
Illinois.
The late Miss Ethelyn Kirk served as Technical Assistant in the Wildlife Research at the Survey.
Richard R. Graber, Jean W. Graber, and Ethelyn L. Kirk theuseoftheUniversitycollections.Wewishtoemphasize our gratitude also to the staffs of the State Museum at Springfield, and the Chicago Museum of Natural History Bird Department.
We owe a special debt to Laurence C. Binford of the California Academy of Sciences, who has loaned us his notes on Illinois specimens in the University of Michigan Museum of Zoology and Kansas University Museum of NaturalHistory,plusothernotesonIllinoisBirds. To the list of persons who have made contributions of fielddataonanumberofspeciesweneedtoaddthenames of Dale E. Birkenholz of Illinois State University, Lawrence G. Balch of Chicago, Mrs. William Carroll, Jr., of Woodstock, Peter Dring of Willow Springs, Everard C. Hall of Chicago Heights, William R. Hawkins, formerly of Carbondale, Marilyn Campbell of the Vermilion County Conservation District, and Natalia Belting of the UniversityofIllinois.Forvaluableinformationononeormorespecies of thrushes, we are grateful to Don Varner of Morrisonville, Paul Heye of Southeast Missouri State College, Robert Russell of Wilmette, Charles Clark of Des Plaines, Alfred Reuss and Karl Bartel of Blue Island, Lee Johnson and Jack Armstrong of Rockford, Mrs. Harry A. Shaw of Sterling, and Elton Fawks of Moline. Elton Fawks also loaned us the notes of John J. Schafer who lived at Port Byron, Illinois, and published many notes on the birds of that area.
Weshouldalsomentionourcolleaguesandassociates oftheNaturalHistorySurveyforhelpwithmanyphasesof the project.
Finally, we should point out that much of what is knownaboutthebluebirdinIlinoisrepresentstheworkof one man, the renowned Illinois naturalist, T. E. Musselman.Wehavedependedgreatlyonhispublishedworksfor ouraccountofthatspecies. ROBIN (Turdus migratorius) (Fig.2and3) SpringMigration Though one may see robins at any season in Illinois, thereareclearlydefinedmigrationsinspringandfall(Fig. 4). There is little in the literature to indicate whether the migration is diurnal, nocturnal, or both. Cooke & Widmann(1883)recordedoneinstanceofnocturnalmigration. We have seen robins migrating in late afternoon (4:15— 6:15 pm CST) in March and April, but whether these flights were sustained into the night, we do not know. We have also observed definite diurnal migrations of robins throughout the morning hours, though more often in fall
Fig.
2.—Robins still largely in juvenal plumage in September.
nspring.[herearesurprisinglyfewreferencestothese matic migrations in the Illinois literature (Armstrong 0, Cooke 1883, Fawks 1967, and Musselman 121) ‘mostofthemlackprecisedataonnumbers,timing,and at directions.
The arrival dates most often given are: February 1-15 southern Illinois, February 6-25 for central Illinois, February 20-March 10 for the north. The earliest arlsarelikelytobemales,butwithinveryfewdaysbirds othsexesarepresent(Speirs1946).Ourcensusesindidthepresenceofhighmigrantpopulationsinsouthern 10is from February 10 to April 10, and from about ch 10 to April 20 in central and northern Illinois (Fig. Xobins banded in Illinois have been recovered on the hernwinteringgroundsaslateasApril5(SouthCaro- ), and March 30-31 (Georgia and Mississippi). In on to the regular spring migration from the South, 5 a on oF nae Fig.
3.—General distribution of the robin,” +} i, al there are winter (December and January) movements of unknownorigin(seeunderWinterRecords,below) Ballou (1880) believed that northward movements of robinsbeganafteraperiodof60hoursofwarmtemperatures (upto 70° F.) and southerly winds. Eifrig (1922, 1924) theorized that photoperiod was a more important stimulusthantemperature.Ourcensusesshowedtherobin’sspringmigrationtobeprolongedinthesouth,asifthe birdstendedtoloiteratthatlatitudeduringFebruary(Fig. 4). This was also Cooke’s (1883) impression. The late February exodus of robins from southern Illinois in 1967 occurred overnight when winds shifted from northwest to southwest.
In general, our spring counts of robins were lower in westernIIlinoisthanfortheeasternsideandmigrantpopulations in northwestern Illinois were especially poor (Fig. 4), aa
i ™ 800 500 »- MIGRATING 200/HR 300 100 10 20 i. ae 9) FEB MAR APR MAY JUNE 600 ‘ a 2 CENTRAL 400 > < Oo * - 4 ac EGG LAYING SeeEZ00 ra) a *¥ = ¥y O e bt 10 20 10 «6 (20:«30'si si‘ 29 a FEB MAR APR MAY JUNE a¢ o 500 _ 1570/HR MIGRATING — t 280/HR T sours 300 100 EGG LAYING (SPAN OF DATES) 10 20 TY ee en FEB MAR APR MAY JUNE Fig. 4.—Egg-laying and migration seasons of the robin in different areas of the state (see Fig. 1). Spring and fall gra (1967-1970) show the highest daily count of each 2 days (left scale). The lines are interrupted where data have not been collect symbols represent counts made in other years or by other observers. Shaded areas show the percent of eggs laid on a given date (rig or the span of dates during which egg laying has been recorded. Dot symbols represent counts made on the western side of the sté without dots represent the eastern side. Arrow symbols indicate dates of actual migration flights and the number of birds seen per ho
4% 3000 MIGRATING — 350/uHR & 300. 100 EGG LAYING y 10 20 30! 9g JULY AUG SEP OCT NOV — 800 — MIGRATING— 0 1700/ HR 600 CENTRAL MIGRATING— 500 NS 350 EGG LAYING / MIGRATING——30-80/uR EGG LAYING
Distribution ThegeneraldistributionoftherobinisshowninFig.3. RobinssurelynestineverytownshipintheState,butasyet the literature does not accurately reveal the distribution (Fig).
ROBIN BREEDING RECORDS NESTS OR YOUNG @1950— A 1900-1950 @ BEFORE 1900 PAIRS OR SINGING MALES (JUNE) O1950— O BEFORE 1900 O Scale 2039 40 SOMiles o_O 10 Fig.
5.—Breeding records for the robin in Illinois.
Singing male records are for June only.
Nesting Habitats and Populations TheearliestreferencestotherobininIllinoiscomment on its domestic nature (Kennicott 1853-1854), and its affinityforhumanresidentialareasasnestinghabitathas probablyincreased(Table1).Ford(1919)notedthatwhile manyspeciesdisappearedasthecityofChicagodeveloped, the robin remained. Carpenter (1935) believed that the robinhadamajorinfluenceontheforestedgecommunity atallseasonsbutwinter.Gates’(1911)classificationofthe robinasadominantspeciesofmixedforestandofsecondaryabundanceinhedgesandorchardsissurprising,and the available census data do not bear him out (Table 1). However, there are no census figures available for any sandy-soilareasinthestate.Adifferenceinnestingha tatsisapparentbetweennorthernandsouthernTIilir’ (Table1).Thereisrelativelylessuseofnonurbanhabit inthesouth,wherenearly80percentofthenestingpopt tionisfoundintowns,versus60-70percentincentral; northern Illinois.
Informationonnest-sitelocationinnorthernand¢ tral Illinois is summarized in Table 2. The list of pli: usedisundoubtedlyveryincomplete.Klimstra&Stieg (1957) provided data on nest sites in Carbondale, Ilir Therearenostudiesthatrelateplantusetoplantavail ity.
:Therecordedheightsofrobinnestsvaryfrom|ton than50feetaboveground.Theliteratureindicatesmi ofnestheightsinnorthernHlinoisaround4-6feet,I( feet,and20-25feet,andaverageheightsofabout7fee ruralnestsand10feetforurbannests.Inbothplaces heighttendstoincreasebyasmuchas3-4feetasthese: passes. The average height of 73 nests in central Illi was10feet,andearly-seasonnestsatCarbondaleaver: about15feet(Klimstra&Stieglitz1957). Wehavefoundnodataonterritorysizefortherob any habitat.
NestingCycle SinginghasbeenrecordedinIllinoisfromlateJan (south) and February (central) to November (Sill 1899and1902,Ridgway1915,andMusselman1939) rarelyatnight(Musselman19305 ForpopulationsinnorthernIllinoisatleast,the|! ingrecordsshowthatrobinshaveastrongtendency turnasbreedingbirdstothevicinityoftheirbirth(F 1945).Publishedbandingdataarelackingforsouther nois,butRidgway(1925)recordedaclub-footedrobu returnedtonesteachyearatOlney.
Thenestingseason(onsetofnestbuildingtofledg lastyoungforthepopulation)lastsfromaboutMarch September 2 with surprisingly little difference ap} betweensouthandnorth.Singlenestingcyclesfora| robinsrequired36-37daysinthenorth(Charles190 Leach1927).Timerequirementsfordifferentphases cycle have been recorded as follows: 3-10 days fo building (Charles 1909, Scherer 1924, Klimstra & St 1957,andDavis1969),11-13daysforincubation(C 1909,Scherer1924,Leach,1927,Labisky1966,and 1969), and 13-15 days for nestling life (Charles. Scherer1924,andLeach1927).
Maximumeggproductionoccursbetweenmic and mid-May in central and northern Illinois (Fig. ‘ dataonthehatchingpeakpresentedbyKlimstra¢ glitz (1957) indicate a similar curve for the south. are no adequate data on clutch size for southern | butinasampleof188nestsfoundinnorthernand) Illinoisweseelittleregionalvariation.Clutchesof: seveneggsarerare,representinglessthan1percer sets.Five-eggclutchesareuncommon,representi percentofthesets(seealsoBlocher1933,andHess