Taste |.—Breeding populations of robins in various Illinois habitats.
Birds Per, Type of Region or Habitat Acres 100 Acres Years Census County Reference lential 8 14 1916 Nest Richland (S) Cooke 1916 20 30 1907-1909 Strip North & Central — Graber & Graber 1963 33 36 South n residential 160 Sy 1957-1958 Strip North Graber & Graber 1963 75 109 Central 98 102 South and estate 100 16 OWES Nest Cook (N) Eifrig 1915 shrub (including hedge) 15 34 IDS 7 OS Strip North Graber & Graber 1963 21 56 Central 22 9 South cet 13 4 1950 Nest Jackson (S) Brewer & Hardy 1950 ard 45 29 1907-1909 Strip South Graber & Graber 1963 36 5 1957-1958 North 78 5 South shrub Py: 28 1966 Nest Vermilion (C) Karr 1968 ) areas 50 4 1907-1909 Strip South Graber & Graber 1963 32 s 1957-1958 North 49 2 Central 126 2 South (all types including edge) 16 6 1907-1909 Strip Central Graber & Graber 1963 60 iS South Ua) 6 1957-1958 North PENG) 6 Central 337) ime South nland forest 12 1966 Nest Vermilion (C) Karr 1968 edge 64 8 1943 Nest Champaign (C) Johnston 1947 55 0-4 1927-1948 Champaign (C) Kendeigh 1944, 1948 55 (0-20 per mile) 1949-1970 Champaign (C) Kendeigh, et al. 1950, Kendeigh & Barnett 1968, Kendeigh & Clemans 1970 d oak-hickory forest 24 l 1967 Nest Hancock (C) Franks & Martin 1967 | growth or cut-over woods 5 14 1937-1938 Nest Rock Island (N) Fawks 1937, 1938 6 8-12 1941-1944 Sangamon (C) Robertson, 1941, 1942, 1944 1 bottomland 93 6 1955 Nest Macon (C) Chaniot & Kirby 1955 figures were converted to read birds per 100 acres or birds per mile of edge (number of territorial males or nests x 2).
ss than one.
hestsreceiveeitherfoureggsorthreeeggs.InApril May,74percentofthenestshavefour-eggclutches, 3 percent have three eggs. In June and July only 46 ntofthenestshavefour-eggclutches,and48percent three eggs. In the south Klimstra & Stieglitz (1957) clutchsizetoaverage3.4eggs.Dataoneggweights venbyDavis(1969). isawidelyheldviewthatrobinsraisetwo,andsomethreebroodsperyear.Thoughpopulationstudiesof d birds are lacking for Illinois, Young’s (1955) data ‘isconsin support this view. The egg-laying curves everalpeaks(Fig.4). obins are rarely parasitized by the cowbird mann1966).Wehavebutonerecord,inasampleof 00nests,ofasinglecowbirdegginanestwiththree ggs.Thehostwassuccessfulinfledgingyoung,but whird egg disappeared. TherearefewIllinoisdataonrobinnestingsuccessand productivity. In the nonurban population we studied in northwestern Illinois (Fig. 1), 58 percent of the nests and 50 percent of the eggs fledged young in April and May (sample:43nestswithcompletehistories),butinJuneand July (23 nests with complete histories) nesting success declinedto48percentofthenestsand37percentoftheeggs. On a school campus in west-central Illinois, Finley (1917) found that only 39 percent of the eggs fledged young in a sample of 64 nests. There are no data on fledging success forthesouth,noraretherequantitativedataonthecauses ofnestfailures.Thecausesmostoftenmentionedintheliteratureorobservedbyusareweather(deathofyoungfrom cold,ordislodgmentofnestsbywindandrainstorms),and predationbygraysquirrels(Sciwruscarolinensis),grackles (Quiscalusquiscula),bluejays(Cyanocittacristata),house cats (Felis catus), and snakes, but the population signifi-
cance of any of these predators is unknown. Lyon (1922) notedparticularlyheavypredationonrobinnestsbygracklesin1922,whennearlyallobservednestsfailed. Finley (1912) and Davis (1 969) have described the growth and development of nestlings.
Taste2.—Plantsandstructuresusedbyrobinsasnestsites in Illinois (mainly nonurban areas).
Percent of Total Nests North Central Nest Site (228 Nests) (84 Nests) Man-madestructures(shed,houseporch,etc.)1612 Osage orange (Maclura pomifera) 10 24 Apple and crabapple (Malus sp.) 8 10 Elm (Ulmus americana, U. pumila, and sp.) 7 10 Oak (Quercus velutina, Q.
borealis, macrocarpa, and sp.) 8 4 Pine (Pinus strobus, P.
sylvestris, P. nigra, and sp.) I 4 Mulberry (Morus sp.) 9 1 Box-elder (Acer negundo) 4 6 Other maples (Acer spp-) 3 6 Cedar (Juniperus virginiana, J.
chinensis, and sp.) 5 2 Cherry, Plum, etc.
(Prunus serotina, and spp.) 2D 4 Hawthorn (Crataegus spp-) s) J Spruce (Picea sp.) 2 2 Hackberry (Celtis occidentalis) 2 1 Willow (Salix spp-) l 2 Honey locust (Gleditsta triacanthos) 3 Lilac (Syringa vulgaris) 3 ; as Honeysuckle (Lonicera spp.) as 2 Birch (Betula nigra, and sp.) 2 oft Rose (Rosa multiflora, and sp.) 1 1 Sycamore (Platanus occidentalis) 2 Pear (Pyrus communis) ae 1 Ash (Fraxinus sp.) 1 Grape (Vitis sp.) 1 Bue Catalpa (Catalpa sp.) “Be 1 Tree of heaven (Ailanthus altissima) Ns 1 Magnolia (Magnolia sp.) ss 1 Pignut hickory (Carya glabra) ar . Golden bell (Forsythia sp.) ats Virginia creeper (Parthenocissus quinquefolia) + Black locust (Robinia pseudoacacia) + 4 Plus symbols (+) = less than one.
FallMigration In early September most robins in central Illinois are stillinmolt,andwehaveseenyoungstilllargelyinjuvenal plumageaslateasmid-October. Smith (1941) reported that young robins were in full migration in northern Illinois by July 21. We have seen robinsflockinginearlyJulywhereverthereweregoodfood supplies,butwhetherthereisanyrealmigrationthisearly we do not know. Robins banded in Illinois have appeared in the Gulf States at least as early as October 8 (Louisiana) and October 20 (Mississippi). Our censuses show marked 10 day-to-daypopulationchangesinJulyandAugustin| tralandnorthernIllinois,butverylittlechangeinsout| Illinois until September (Fig. 4). We have not witne active migrations of robins in any part of the state 1 September,butRobertD.Crompton(personalcomm: cation)hasseendiurnalsouthwardmigrationasear! August11inMasonCounty.Themostmassivemigrat we have seen occurred in October in northern and ce Illinoisnearmajorwaterways.Thoughallofthefallr) migrations we have seen were oriented either near s (180°)orwestofsouth,therecoveriesofbandedbirdss greatdispersal(Fig.6).Wehaveseenmoremorning| rationsofrobinsinthefall,andmoreeveningflightsi1 spring. The robin is a rare casualty at television tov We have found only one specimen (on October 6, | among thousands of night migrants (of other spe: pickedupattowersincentralIllinois._ Highest fall populations occurred in September October in central and northern Illinois, and in Oct and November in the south (Fig. 4). Fall counts of ~ werethreetofourtimeshigherineast-centralIllinois in the west.
In the north we saw about four robins in the (August-October, inclusive) to one in the spring (M andApril).Inthecentralsections,botheastandwes saw only about 1.5 in the fall to one in the spring. I souththeratiowas,inexplicably,reversed:threeins| (February through April) to one in fall ust-November, inclusive). These data represent “rounded”robins,andnotbirdsinactivemigration. Anotableecologicalchangeoccursintherobinbet spring,whenmostbirdsarefoundforaginginopen¢ land, and fall and winter when the population freq woody habitats much more.
Roosting We have no records of Illinois robin roosts that approachthedimensionsofthosefoundineastern: souri, where as many as 3% million birds have bee ported(Petersen1965,andWidmann1895).James( studiedlocalroostsinChampaignCounty,androosts alsobeenrecordedinCookCounty(Back1934-193: Bailey 1932), and in Fulton County where the popu peakedat22,500birdsonOctober23.Roostingags tions occur inspring from March into May, andi summerandfallfromJulythroughOctober(James1 Large winter roosts should be looked for especia southern Illinois. | WinterRecords Robinshavebeenfoundinwinterthroughoutn the state (Fig. 7), but generally only in small nul northofthesouthernzone(Fig.8),andthebulkofth ernrobinpopulationwinterssouthoflatitude35° i.e., south of Illinois (Speirs 1953). Though there a! cemberandJanuaryrecordsfortheChicagoareain. 3ofthepast40years(1930-1969),ourstatewidece
Fig.
6.—Distribution of recoyof robins banded in Illinois.
-and shaded areas indicate the d of recoveries from five bandations.
ROBIN band recoveries edthat99percentofthestate’swinterrobinpopulavasinthesouthernregion(Graber&Graber1963). ome winters (note especially 1955-1956, 1964-1965 g.8)largenumbersofrobinsappeareveninnorthern entral Illinois. In such high years hundreds or even sands of robins may be seen per day incentral and ern Illinois (Fawks 1967, Musselman 196309 ink Mayfield 1951, and Rice 1946). Various explanahave been offered for these high populations, and aresomedatatosupportthefollowinghypotheses: nusuallyhighproductivityintheprecedingbreeding n, productivity that increased population pressure whereintheeasternUnitedStates;(2)exceptionally winterfoodreservesinthenorth;and(3)exceptionallynorthwardmigration,reflectinganunusuallymild r(Robbins1956,andNolan1956). 00ke(1885)believedthatbottomlandforestwasthe Sprimarywinterhabitat(notealsothewinterdistri- 1,Fig.7),buttherearefewpopulationmeasurements ble for any habitat. Between 1927 and 1970, Kenandhisstudentsreportedpopulationsinforestedge ntral Illinois ranging from none in most years eigh1948)toeightbirdspermileofedge(Kendeigh St 1958). In southern Illinois, Shawetal. (1961, © BANDING STATIONS @ NOV.
-- FEB 4MAR.--APR.
O MAY -- AUG.
WYSEP--ocr.
ay 300 400 MILES * aioe = ae = PR greet « "1 as) 1965)recordedpopulationsinashrubbyfieldrangingfrom none(1961)to13robinsper100acres(1965). FoodHabits Forbes’ (1903) studies were based almost entirely on specimensfromcentralandnorthernIllinois.Inthespring robins fed almost exclusively on animal matter (Fig): Theitemsmostfrequentlymentionedintheliteratureare earthworms and larvae of March flies, especially Bibio albipennis (LeBaron 1853-1854, Thomas 1920, Rice 1946, andT'womey1945).Forbes’studiesshowedtheBibiolarvaetobeimportant,butdidnotshowtheexpectedprevalence of earthworms (Fig. 9). He related the low tally of worms to their quick digestibility. Cutworms (Noctuidae), andeventheeggmassesoftussockmoths(Liparidae)are prominent in the diet (Hulsberg 1917-1918, and Schantz 1933), as are ground beetles (Carabidae) and wireworms (Elateridae) later in the spring. At a Tazewell County orchard that was heavily infested with canker worms (Geometridae),Forbes(1883)foundthatrobinsincreased their intake of the pest, but kept many other items of their usual diet. Cleveland (1923) found robins feeding 17-year cicadastotheiryoung.
ROBIN WINTER RECORDS DEC.1—JAN.
31 wy JO Ee Renae 2 | : Ul @ 1950- daaaiony -) iad So a Tt mee Ea 9 = A 1900- 1949 woe) gic | A oh es | Ane 8 ele. \ mia ® ® BEFORE 1900 ye el gE al > A> oe jen OALL, f BURE / os gmk 1 UE HE Y @ | Oy |S c@ce|_pubnam| ay | ‘ ee > + STARK a a Lay BHALL i} 3 ' KNOK | i :
& | warren | LIVIN GSTON } 2coRivAWOODFORD ¥ es =| —_—-o e Set i McOONOUGH| FULTON URES A EAN FORD A Rea Sa | d es eS a AL ) N tLe, ASON rere pies Galt: it 7 SCHUYLER OE WITT“ aN “@ f= | s q AN DAMS 4 MENARO a we oa | aie \' prow co 4 SS ‘aa ‘ e- a = aye: A =} [oovous ‘ PIKE scorrh ia Es ru sie © eae ian =a | ee | pt | + “ey | et GREENE | | |i tare / ped uc Bin MONTGOMERY re | A/ YS MADISON ST.
CLAIR MONROE Fig.
7.—Winter records for the robin in Illinois.
The three regions of the state discussed in the text are shown by heavy lines.
In June a change to a primarily fruit diet occurs, and fruit (much of it wild) is very important through the rest of the summer and fall (Fig. 9). In late summer and fall (particularly October) we have observed robins feeding heavily on wild grape (Vitis sp.), black cherry (Prunus serotina), Parthenocissus, hackberry (Celtis sp.), dogwoods (notably Cornus racemosa, C. rugosa, and C. stolonifera), multiflorarose,pokeberry(Phytolaccaamericana),elderberry(Sambucuscanadensis),persimmon(Diospyrusvirginiana), and red cedar (see also Hulse 1912, Bell 1956, and Cone1963).Otherfruitscommonlyrecordedasrobinfood are:mountainash(Sorbussp.),sumac(RAussp.),barberry (Berberissp.),bittersweet(Celastrusscandens),holly(Ilex decidua), snowberry (Symphoricarpos sp.), pear (Pyrus sp.),apple(Malussp.),andgreenbrier(Smilaxsp.)(Cooke 1885, Musselman 1934-1935 and 1963, Holcombe 1936, and Pitelka 1936). At least one instance of robin intoxicationfromfermentedhackberrieshasbeenrecorded(Buck 1936). Forbes’ (1903) only winter specimen (from Cairo) containedfruitofmistletoe(Phoradendronflavescens)ex- 4 clusively,butlocalobserversfeltthatwinterrobinpor tionsinthatareadependedmainlyonwildgrapesand afailureofthegrapecropwasreflectedinreducedWw populations.Cooke(1885)alsonotedthatrobinsfedhi lyonwildgrapesinsouthernIllinois. Forbes (1900) believed the robin to be function; controllingcutwormnumbers,andRice(1946)estim thatrobinsconsumedaboutfive-sixthsoftheinvertel population in leaf litter at a forest edge in Champ County.
Charles(1909)recordedthatbothadultsfedtheyo putting in a 15-hour day in late May, and bringin averageof356piecesoffoodperday.LepidopteraI< comprised about 50 percent of the total food, with e worms (about 29 percent), ants (about 7 percent), Di (about 6 percent), and small percentages of Coleor Myriapoda,andadultLepidopteramakingupmost¢ other half. Earthworms as food for the young have beenrecordedbyMann(1908)andScherer(1924). Longevity and Mortality BasedinpartonnorthernIllinoisbandingdata,F (1945a)determinedtheaveragenaturallongevityfor: intobe1.7years.Heestimatedtheagegroupcompo for the population as follows: first-year birds, 53 pe second-yearbirds,25percent;third-yearbirds,lessth percent; fourth-year birds, less than 6 percent, fiftt birds,lessthan2percent;andsixth-yearorolderbird than1percent.Asampleof28returnsofrobinsbanc northeastern Illinois produced six birds past 3 ye age, one past 4 years, and one past 6 years (Dov 1949). A robin, recognizable because it had white feathers,wasseenregularlyinthebreedingseasonat dale in 6 successive years (Tuttle 1927), and Ba (1968)oldestbandedrobinwasnearly5yearsolds| AstothecausesofrobinmortalityinIllinois,the| turehasdealtindetailwithonlyonetype—insectici¢ soning.Bartel’sstudiesinCookCounty(1960,1962,| areparticularlyvaluablebecausehestudiedabande ulationforwhichhehadalong-termpopulationreco! establishedthat85-90percentoftherobinpopulatic eliminatedfollowingapplicationof2poundsofhept peracreforJapanesebeetle(Popilliajaponica)cont year after treatment the robin population had rec: only5percent,but2yearsaftertreatmentitwasbacl percent of the pretreatment level (Bartel fide Mu 1960 and Graber 1962). | Arobinpopulationwaseliminated(asevidenced| recoveryofdeadbirdsandthedisappearanceofrobin establishednests)inanareaofIroquoisCountybyt plication of 3 pounds of technical dieldrin per acre, forJapanesebeetlecontrol(Scottetal.1959).Large bersofdeadearthwormswereseenfollowingthetrea andthiswasbelievedtobetheroute-sourceofthet¢ inrobins(seealsoBarker1958).Veryhighrobinm¢ from DDT application has also been re (Montgomery 1956).
Severeweatherinlatewinterorspringmaybea’
4. NORTH —— CENTRAL——~— SOUTH —— b Ze it 0.8 0.6 |!
I 0.24] | } UU DNINDEAN 1930 1940 1945 1955 ROBIN-FOOD NOPTERA (esp. ants) OPTERA (esp. Noctuidae) RA (esp. march & crane flies) 60 40 20 DPTERA (esp. ground S$, Scarabs, click s, & weevils) TERA (esp. stink bugs a Saar] < DPTERA 8 NIDA uw PODA e forms 5 3 (sp. grapes, black_ , & cherries) 50 30 10 NO OOOIOD FEB MAR APR MAY JUN JUL AUG SEP OCT - I.—Food habits data on the robin from the study of Forbes, 880), Percentages represent the part of the total food identified in lachs of several robins examined each month. Fig. 8.—Annual variation in winter robin populations, based on Audubon Christmas counts in three regionsofthestate.Graphline shows the number of robins seen per party hour. (For information about the Audubon Christmas counts, see Cruickshank 1970.) 1965 icant mortality factor in robin populations, as it is in bluebird populations. Dead robins and reduced populations have been recorded in northern Illinois following severe wind, cold, or snow, especially in April (Butler 13.0 67 Blocher 1921, Schafer 1921, and Segal 1960). Roseberry (1962) found robins among the dead birds picked up near Carbondale following prolonged snow and cold in FebruaryandMarch. VARIED THRUSH (Ixoreus naevius) (Fig. 10) Becausethereareatleast16recordsofthisspeciesfrom 14differentlocalitiesinthestate,itsoccurrencecannotbe consideredaccidental.Onlyonerecordwasfoundintheliterature before 1950 (Fig. 11) and there were four in 1970 (Armstrong 1970). All records are from northern Illinois with the exception of one wintering at Decatur (Lobik 1957). All dates given fall between mid-December and March 30 with one exception (April 26, 1929 at Blue Island,Bartel1932). Theusualpatternofbehavioristhatasinglebird,most oftenamale,willappearatafeeder(orareaprovidingfood suchascrabapples)aroundChristmastimeandremainfor severalweeks.Thisfarnorthwesternbreederseemstobea habitual winter wanderer, occurring fairly regularly in northeasternUnitedStatesandspottilyasfarsoutheastas theGulfCoast(Keith1968).
eS Fig.
10.—Male varied thrush photographed near Rockford, Hlinois in January, 1970 by Jack Armstrong. This is a valuable photographic record of a species rare in Illinois. ‘The bird is actually about the size of the robin. VARIED THRUSH WINTER RECORDS eae | Seer sare a @ 1950 — SOLD AMES) rere | WINNEB AL 3 aan “wing ee Pd A 1900- 1949 common | ge ae ee ail — DE KALB = at ° e'°.
fa ae ye Ie ak aire iE a wes wale > mare | | IROQUOIS ee | Fe TAZEWELL 1 eS Vv | ae | 'ULTON | Me LEAN hee! alae oe By iF — — MASON Tt ae YLER ecan | CE MID CHAMPAIG! | MENARD cass F ic ae ese att eres SANGAMON eee nares ' ae at co COLES | | GREENE | aff MMACOUBIN MONTGOMERY CLARK PUMBERLAND EFFINGHAM € | JASPER |cnawrond CLINTGN WASHINGTON ait pace:
RAWDOLPH JACKSON |yexumson| SALINE (GALLATIN UNION. ~JJOHNSON|P O PE nano Scale to__O 10 20 30 _ 40 SOMiles SM, O74Ne pons” Fig.
11.—Winter records for the varied thrush in Illinois. 14 WOOD THRUSH (Hylocichla mustelina) (Fig.12and13) SpringMigration The available evidence, notably fall kills at tele towers, indicates that wood thrushes are night migi butwehaveneverheardarecognizablewoodthrus amongthemanyCatharuscallswedetecteverymig} season in Illinois. : | March records for this species (George 1968) mi accidentaleveninsouthernIllinois,andshouldbecare ly documented with full details. We are skeptical eve) earlyAprilrecords(Ford1956,andSparks1905),espec ly in northern and central Illinois. In most years they woodthrushesreachsouthernIllinoisaboutApril15 tral Illinois about April 22, and northern Illinois i} April29.Withinaweekthespeciesbecomescommo) peak numbers may be seen in all parts of the state May 6-20 (Fig. 14). Wesawthelargestnumbersinthesouthandfewe the north, and our counts in southern and central were consistently higher on the western side of the thanontheeasternside(Fig.14). TherearenopublishedbandrecoveriesofTilinoi: thrushes for any season. Distribution Thegeneraldistributionofthewoodthrushis$ Fig. 13. The breeding distribution in Illinois is ver known,especiallyinanyquantitativedetail(Fig.15 Nesting Habitats and Populations this problem is much more critical now. Cahn (1929) mentioned that wood thrushes breed in swamps. Thespeciesalsonestsinuplandforest,andeve dential habitat and shrub areas (Table 3). Riis Gault(1933),andMusselman(1921a)reportedg¢ ing populations in northern and western cities, but recentlywefoundmeasurableurbanpopulations the south (Graber & Graber 1963). = Wood thrush territories in central Illinois fore sured by Twomey (1945), Fawver (1947a), ane (1953) varied from about 2 to 7 acres. The most data are those of Calef who found extremes of 1. acres, with an average of about 3 acres. q There are nest site data on only 29 nests. | mostfavoredwereelms(31percentofnests)and (17percent).Althoughheightsofnestsrangedfrom feet,mostofthenests(71percent)were5-10feethigh
12.—Wood thrush, the most heavily spotted of Illinois thrushes.
° 200 400 600 miles NestingCycle The Illinois literature is essentially devoid of quantitativedataonthenestingcycleofthewoodthrushandwecan add little. Singing has been recorded from April 19 in southern Illinois to August 3 in the north. Our records on the span of dates for egg laying, from April 26 in the south to July 19 in the northern and central regions, are very incomplete, particularly for the south. A record of young leaving the nest May 30 in the Chicago region (Ford 1956) mustbeexceptionalasanearlynestingrecordforthatlatitude.
There is a very high incidence of cowbird parasitism. From our records and the literature, we have egg data on only 69 wood thrush nests in Illinois, of which 33 (48 percent)wereparasitized.Mostofthenestshad1or2cowbird 16 800 eo tm x & x s nc roe AA tn x Ri , = e A Fig. 13.—General distribution of the wood é thrush.
oh ae y y 5 Ranges~——-- | ee 4 = == * Bt BREEDING ~* a a a ES winter : + S&S - ms s e ae: é ae eggs,but6nestshad3ormore(upto5).Thoughthe pleissmallitrepresentedallthreeregionsofthestat theincidenceofparasitismwasnear50percentinea gion. This high parasitism has been reported over years. Mundt (1883) found nearly half of the nests the Vermilion river bottoms parasitized. Twomey | recordedfledgingsuccessof78percentfor23thrush€ nests),and33percentfor3cowbirdeggs(3nests).: Inthesampleof36nonparasitizednests,clutcl wereasfollows:5-egg,9percent;4-egg,76percent,| 15 percent. | Therearenodataonlongevityoronmortalityf Montgomery(1956)feltthatwoodthrushessurvived than robins following DDT applications for elm d becausethewoodthrushesarrivedlateraftertheins treatment.