FLEDGING AND MIGRATION OFJUVENILE BALD EAGLES

82MCCLELrm' D EX AL.VOL. 30, No. 2Table 2. Telemetry and sighting locations of eight radio-taggedjuvenile bald eaglesduring autumn and winterafter departure from nesting territories in and adjacent to Glacier National Park, Montana. Distancesin parenthesesare for more than one day. Last known distancesfrom nestsare in bold. Locationson dates after shortdistancemovementsare not listed. Locationsfor Eagle 14 are not shown;it moved south only 132 km, to FlatheadLake (see Fig. 3).EAGLE NUMBER,YEAR MARKED, ANDOBSERVATIONDATESEagle 01 (1985)26-27 Sep 198529 Sepa10 Oct aEagle 02 (1986)5-7Oct 1986LOCATION(NORTH LATITUDEWEST LONGITUDE)kmMOVEDHungry Horse Reservoir;MT (48014' 113ø50')cPlacid Lake, MT (47007' 113ø31')cNestNear Silver Star, MT (45042' 112018')10 km N Dillon, MT (45017' 112045')(184)(6o)-aa9Hungry HorseReservoir;MT (48ø14' 113050') cNestMeadow Creek, South Fork Flathead River (47052' 113026' )126522008 Oct Near Anaconda-PintlarMtns., SW Philipsburg,MT (46003' 113038')0 OctNear Bannock Pass,MT/ID border (44048' 113019')143-384LoggingLake, GlacierNational Park, MT (48046' 114ø01') cFirefighter Mtn., Hungry Horse Reservoir,MT (48019' 113052') cGreenhorn Mountain, W Helena, MT (46043' 112017'10 km N Ashton, ID (44012' 111%1') cNestTeton Pass,WY (43029' 110ø59') (101)-561soaring(109)23 Oct07's secondfall; first locatedSW Kalispell,MT (48ø11 114ø29')Along Clark Fork Rive ;near St. Regis,MT (47018' 115ø05')cNear SelwayRiver,E Lowell, ID (46006' 115016')26 Oct aW "He Devil Mountain," OR (45019' 116ø41')(163)Eagle07 (1986)20 Sep 198622 Sep 23 Sep25 Sep-1 Oct 53(212)289Eagle0719 Oct 198721-22Oct 3 Nov5 Nov7-8 Nov9 NovEagle 08 (1986)20 Jan 1990bNear Malheur River,N Juntura, OR (43046' 118006')8 km E Upper Alkali Lake, CA (41040' 120001')28 km NE Mount Observation, NV (40055' 119056')Soaring 15 km SSEfrom Mount Observation,CA (40039' 120005Logging Lake, Glacier National Park, MT (48046' 114ø01')S Fork BoiseRive ; below Anderson Dam, ID (43022' 115ø32')dEagle 09 (1988)6 Jan 1989 CycloneLake, MT (48042' 114018')Eagle 52 (1988)Lake McDonald, Glacier National Park, MT (48038' 113ø52') 21 km S Canada border, Koocanusa Reservoir, MT (48049' 115ø09')24-27 Sep 1988a28 Sep29 Sep 30 Sep1 Oct ' 11-15Oct2 Dec-29 Jan Eagle 95 (1988)2-3 Sep 1988 4 Sep 5 Sep6 Sep7 Sep8-10 Sepa11 Sep13-15 Sep16 Sep134(207)(233)(lO5)27-1 021Nest6OONestLake Roosevelt,near Kettle Falls, WA (48034' 118ø05')c.dNest10310 km N Sandpoint,ID (48019' 116ø34')c110Selkirk Mountains, 16 km E Lake Roosevelt,WA (48007' 118ø01')Columbia Rive ; 32 km NW Grand Coulee, WA (48004' 119022')'5 km NW Dartington, WA (48016' 121ø39') S end SkagitRiver Delta, WA (48018' 122024')Near StillaguamishRiver,near Arlington, WA (48ø10' 122ø03') ½Lake McDonald, Glacier National Park, MT (48038' 113ø52') KoocanusaReservoir,U.S./Canada border (49001' 115ø10')½110Near Dewar Creek, 42 km W Kimberly,BC, Canada (49039' 116ø34')Near Trout Lake, BC, Canada (50035' 117024')Columbia Rivex;7 km N Revelstoke,BC, Canada (51002' 118ø1Y)AdamsRiver at ShuswapLake, BC, Canada (50054' 119ø34') Nicola Lake, BC, Canada (50013' 120ø30') FraserRiver,3 km W Hope, BC, Canada (49022' 121ø29')cSquamishRiver,55 km N Vancouver,BC, Canada (49044' 123ø09')MountainsW SquamishRiver, BC, Canada (49053' 18(136)(154)-685

JUNE AGLE NUMBER,YF R M m D, NDOBSERVATIOND TESEagle 93 (1991)10 Sep 199111 Sep12 Sep13 Sep 14 Sep 17 Sep18 Sep 21-29 Sep1 Octkm MOWDLOCATION(NORTH LATITUDEWEST LONGITUDE)NestLake McDonald, Glacier National Park, MT (48ø38' 113ø52')c29 km WSW Pincher Creek, AB, Canada (49ø26' 114ø18')Chain Lakes,AB, Canada (50ø15' 114ø15')(100)12097Soaringat W edgeCalgary,AB, Canada(51ø06' 114ø15')E Bow ValleyProvincialPark, AB, Canada (51ø07' 114ø58')cSoaringup ElbowRiver,AB, Canada (50ø44' 114ø51')Near Tally Lake, MT (48ø24' 114ø35')S SwanLake, SwanValley,MT (47ø53' 113ø51')c5851(274)10195Lake McDonald, Glacier National Park, MT (48ø38' 113ø52') (356)(152)5-19OcPSE White SulphurSprings,MT (46ø27' 110ø50')Hyalite Canyon,S Bozeman,MT (45ø27' 110ø57')W MadisonJet., YellowstoneNational Park, WY (44ø39' 110ø56')Near HenrysLakeoutlet,ID (44ø36' 111ø23') 22-29OctHarriman State Park, Island Park Reservoir, ID (44ø23' 111ø28') 26Along HenrysFork River,W Ashton,ID (44ø04' 111ø30') 35-55530cP4 Oct1 Nov9037Sightingand telemetry location on this date.Sightingonly.Roost location.Autumn migration routesunknown.line toward the adult, vocalizingcontinuously.During the first week, we occasionallyplaced fish onthe lake shore, out of the juvenile's view, but at alocation toward which it wasmoving. It fbund andate most of the fish we lefL Seven d afier the premature fledging, the adults began to make preydeliveriesalong the lake shore.The fledgling'sfirstsustainedflight wason 12 Augustand on 19 August t returned to the nest. On 3 Septemberwe recaptured the fledgling, remeasured it, and fitted itwith a wing marker (code A-07). Since its initialcapture 34 d earlier, its weight had increased by29% (fi'om 4.2 to 5.4 kg). All featherswere fhllyemerged, increasing the wingspan by 25 cm andscribeswhat we also observed: "As the young gotolder, the parents spent lesstime in their vicinity.Youngwere not seenhunting, but depended upontheir parents fbr fbod. They begged and chasedtheir parents throughout the postfiedgingperiod,with higher intensityat the end. Nevertheless,theadults became progressivelymore reluctant to feedthem ."Initiation of Migration. Juveniles began migration from natal territories between 22 August and5 October (median 9 September, N 15, Table1). Departure time varied from 0730-1942 H, butseven occurred afier 1200 H (median 1300 H,N 9). The interval between ficdging and migra-tail lengthby 8.5 cm. Ultimately,eagle07 provided tion varied from 32 to 70 d (median 42 d, information during the subsequent two autumnmigrations.BetEre migration, all fledglings generally remained within 1 km of their nests and appearedto be tora!!ydependent on adultsfor food. In theimmediate postfledgingperiod, adultsoften delivered food to the empty nest, after which the fledglings flew to it to eat. Wood (1992) alsodescribedbald eaglefledgling dependenceon adultsin Florida. Alonso et al.'s (1987:212) descriptionof therelationship between adult and .juvenile Spanishimperial eagles (Aquila adalberti)appropriatelyde-46 d, SD 9.0, N 15). The mean interval forthe four prematurelyfledged eagletsalsowas46 d.Meanintervalsin otherstudieswere24 d in Cali-fornia (Hunt et al. 1992a), 49 d in Maine and Florida (McCollough 1986, Wood 1992), and 52 d inSaskatchewan (Gerrard et al. 1974).Autumn Migration Routes and Wintering Areas.We documented autumn migration routes and/orwintering areas fbr nine juveniles (Table 2). Sixjuveniles moved primarily south and three movedpredominantly west on their first migrations (Fig.1). The southward routes were similar to those

84MCCLELLANDETAL.VOL. 30, No. NIANEVADAEAGLE01' IEAGLE02-k'IEAGLE07 IEAGLE08O IEAGLE09-)It.IEAGLE14 ' IEAGLE52 IEAGLE93ßNFLATHEAD LAKEEAGLE95ßFigure1. Autumnmigrationroutesandlastknownautumn or winteringlocationsof bald eaglesfrom natalareasin and adjacentto GlacierNationalPark (G symbol), Montana.Two routesare shownfor eagle07; theFigure'2. Autumnmovementsof juvenileeagle14 inroute farthesteastis autumn 1986 (juvenileyear) and the1989, from the natal area at BowmanLake (B symbol),route farther west is autumn 1987 (secondyear). Migrain Glacier National Park (G symbolwith boundaryshowntion routesfor eagles08 and 09 (winteringareasshown) as dashedline), Montana, to wintering location at andwere unknown. A more detailed route for eagle 14 isnear Flathead Lake, Montana. Note eagle 14's passageshownin Fig.'2.The Tnigrationrouteof eagle93 isshown through the former kokaneesalmonspawningarea atseparatelyin Fig. 3.Lake McDonald. Dotted line identifies the ContinentalDivide.of juvenilespreviouslyradiotrackedfrom autumnthroughBritishColumbia.Duringone period,weOnlyeagle14 remainedwithinthe generalvicinity followedeagle95's signalon the groundfor 380of GNP, wintering near Flathead Lake, 132 km km through British Columbia, making frequentsightings.Eagle 52 took a relativelydirect route,south of its natal area (Fig. 2).Eagle09's routewestfrom GNP wasunknown, south of the Canadian border, to western Washingbut it was found at Lake Rooseveltduring a mid- ton (Fig. 1) and it remainedin the Skagitand Stilwinter watertbwl census of northeastern Washing- laguamishRiverareasthroughoutthe winter.Onton (W.R. Radke, U.S. Fish and Wildl. Serv.,pers. somedays,its transmittersignalwasmonitoredbuildingof North Cascadescomm.). In the KettleFallsDistrict,where eagle09 fi:omthe headquartersconcentrations in GNP (McClelland et al. 1994).wintered, 98 bald eagleswere observedon the1989 winter count (G. LeBret, Natl. Park Serv.,National Park in SedroWoolley,Washington(C.R.Wasem,Natl. Park Serv.,pers.comm.). Servheenpers.comm.).Eagles52 and 95, both fi:omthe and English(1979) and Hunt et al. (1992b) pre1988 Lake McDonald nest, were tracked west to viouslydescribedeagleuseof the SkagitValley,thePacific coastalwaters in Washingtonand British vicinityin whicheagle52 spentpart of the winter.Columbia. Eagle 95 followed a curving pathThe westwardmigrationof threeGNPjuvenileswas

JUNE1996JUVENILEBALDE GLEMIGRATIONsimilar to the pattern described by Harmata andOakleaf (1992). They reported that most of the 21juvenilestrackedfrom the GYE migratedwestward,primarily to Washington and Oregon.It is curious that both 1988 Lake McDonald juveniles moved independently westwardfrom theirnatal area, whereas the 1991juvenile moved north,then south. Harmataand Oakleaf(1992)BRITISH COLUMBIAß'Ca'CALGARYiALBERT .andHunt et al. (1992a) discussedthe theory of geneticmemory suggestingthat juveniles may have a genetically-basedpropensity to migrate to a particular destination or in a particular direction. The1988 and 1991 Lake McDonald juveniles were offspring of different male parents (fate of the firstmale was unknown). This may imply that the genetic code for migration direction is distinct in different parents, perhaps additionally suggestingdisparate natal areas of the 1988 and 1991 male85I -I -MONTANAadults.GNP juveniles moved west ( 98 km/d, N 16 d, two eagles)and south ( 87 km/d, N 35d, five eagles) more slowlythan northward migrating juveniles tracked from California ( 130 km/d, N 14 d, coastal route; and 184 km/d,WYOMINGN 21 d, mountain route) by Hunt et al. (1992a).The five California eaglesreportedly moved a considerabledistanceeach day, whereas the GNP juvenilescommonly stoppedfor one to severaldaysat foraging sites. Eagle 93, from Lake McDonald, Figure 3. Autumn migration of juvenile eagle 93 ininitially moved north (Fig. 3) on a route similar to 1991, from the natal area at Lake McDonald, Glacier Nathat used by most spring migrants studied by tional Park (G symbol),Montana. After first moving 18McClelland et al. (1994). After traveling 408 km km east to Granite Park, GNP, eagle 93 traveled 408 kmI3ookmnorth in 5 d ( 82 km/d), it reversed direction,returned to GNP ( 74 km/d) for 10 d, thennorth, to the vicinity of Calgary, Alberta, Canada, thenreturned to Lake McDonald before southwardmigrationmoved more typicallysouthward,into Idaho ( to Idaho.106 km/d in 6 d).Lack of food in natal areaswas not the majorinducement for migration of GNP juveniles. Manyjuveniles migrating southward from Canada wintered in northwesternMontana,in some of thesame vicinities that GNP juveniles vacated earlierin the autumn (McClelland et al. 1994). Additionally, the juveniles we tracked appeared to be migrating alone, apparentlyguided by instinctratherthan following older eagles. Their parents remained on the nesting territories well beyond thejuveniles' departure (Yates 1989). These factorsalso support the hypothesisof genetically determined migration patterns for most GNP juveniles.Participation of GNP Juveniles at Autumn Goncentrations in GNP. During the first year of ourstudy (1985), migrating bald eaglesfrom Canadacontinued to congregate at the autumn spawningrun of nonnative kokanee salmon along I MC(McClelland et al. 1982, 1994). In 1985, there werean estimated 118,000 salmon in LMC on 29 Octo-ber. Eagle 01, ti"m the Hungry Horse nest only 20km south of the sahnon run, began migration on26 September heading south away from the concentration when there were at least 10,000 salmonin LMC. However,in the early period of spawning,few salmon were dead or easily accessibleto.juvenile eagles (Bennetts and McClelland 1991). Thepeak eagle count (520) occurred on 5 November,when eagle 01 had moved at least 360 km south ofthe concentration (McClelland 1992).In 1986, the salmonpopulation in Flathead I ake

86MCCLELLAND ET AL.(from which the LMC spawningrun came) begana precipitouscollapse(Spencer et al. 1991). However, there were still 21,500 salmonin LMC at peakcount on 7 October. Two juveniles from LoggingLake, 25 km north of LMC, were potential participants at the concentration.Eagle 08 departed on6 September.Although its migration route wasunknown, we monitored for its signal daily in GNPand it did not passnear LMC. Eagle 07 flew directly over LMC on 20 September,when there were 1,000salmon in LMC, but it continuedsouthwithout stopping.Eagle 02 left Hungry Horse Reservoir on 5 October when the salmonwere nearingpeak numbers in LMC, but it migrated southwardawayfrom LMC. Basedon the movements of thesefour juveniles, there seemed to be no inherent attraction to the salmon in LMC. By 1988, when wetracked the departure of five juveniles (none ofwhich went to LMC), the salmon population hadcollapsed and only 120 salmon were counted inLMC; in 1991, no salmon were recorded.Only eagle 14, in 1989, exhibited movementsthat might be interpreted as searchingthe LMCarea for salmon (Fig. 2). During 17-23 October1989, eagle 05 (from the 1988 Logging Lake nest)joined other migrating eaglesat a kokanee salmonspawningrun at Kikomun Creek, near Elko, BritishColumbia, 100 km northwest of GNP.VOL. 30, NO. 2All juveniles moved into Canada or were movingnorth near the border when last located; theyprobably spent their first summer in Canada.Somecouldhavereturnedto theU.S.afterlast docu-mented locations, but we consistentlymonitored inGNP without success.The timing and routes ofGNP juvenile migrations in spring were similar tojuveniles, probably of Canadian origin, previouslytracked from GNP autumn concentrations (McClelland et al. 1994). We had insufficient data tocharacterizethe general rate of spring migration.However, eagle 06 traveled 826 km in 9 d, movingnorthintocentralAlbertafromtana. This rate (i 92 km/d)autumnmovementsnortheasternMon-is similar to thewe documented.During summer 1989, eagle 52 (which had wintered in westernWashington) stayedat the CrestonValley Wildlife Management Area, British Columbia, Canada. On many days, its signal was monitored from the visitor center or sightingsweremade providing specialeducationalopportunitiesfor Management Area visitors (D. Ransome,AreaInterpreter, pets. comm.). Through summer 1995,no marked GNP juvenile had returned and remained in a natal area. Only eagle 14 wasreportedin adult plumage in GNP; it was observedat SaintMary Lake on 26 April 1995 (G. Dicus, Natl. ParkServ., pets. comm.). It was not associatedwith aWe concluded that most GNP juveniles did not nest and was 37 km from the Bowarian Lake nest,participate in the autumn bald eagle concentra- from which it fledged in 1989. Eagle 14 apparentlytions at LMC, even during the years of salmon did not remain for the summer. Harmata and Oakabundance (1963-85). Migration from natal areas leaf (1992) reported that GYEjuveniles that hadwas initiatedbeforethe time most salmon werewintered near the west coastreturned in the springavailable at LMC. Most GNP juveniles seem to be to the GYE and remained through the followingprogrammed to migrate to wintering areas far autumn. Mabie et al. (1994) reported that migrafrom their natal areas.Juveniles migrating south- toryjuveniles from their studyarea in Texasexhibward from Canadaopportunisticallyparticipatedin ited fidelity to natal nesting areasfor breeding.the GNP concentration (McClelland et al. 1994),Foraging During Migration. Although juvenileswhich lastedonly 50 yr; perhaps this wasan insuf- usuallywere observedalone during their migrationficient duration to influence inherited migration flights, they often joined other eaglesat foragingsites,especiallywhere food wasconcentrated.Folpatterns of GNP juveniles.Survival, Spring Migration, Summering Areas. lowing radio-tagged eagles allowed us to observeTen of the 11 radio-taggedjuveniles were known previously undocumented food concentrationsto survive at least through their first winter. The that attracted eagles. For example, during springfhte of one juvenile was unknown. Harmata and migration 1989, eagle 06 was observedalong theOakleaf (1992) reported 80% first yr survivalof Missouri River between Ulm and Cascade, Montana, with as many as 45 other bald eagles.Theyjuveniles in the GYE.We documentedspringand/or summer locations for nine juveniles (Table 3, foraged on ground squirrels,fish, waterfowl, andFig. 4). Four juveniles passed through or within carrion (Caton et al. 1989).severalkm of GNP en route to Canada. On 6 AprilWe did not quantitatively assessforaging, but1990, eagles05 and 14, moving north from differ- during migration we documented eagles feedingent wintering sites,were both at Kintla Lake, GNP. on or perched near carrion of antelope (Antiloca-

JUNE1996JUVENILEBALDEAGLEMIGRATION87Table 3. Telemetry and sightinglocationsof eight radio-taggedjuvenile bald eaglesfrom nestsin and near GlacierNational Park, Montana during springand summer.Distancesin parenthesesare for more than one day.Last knowndistancesfrom nestsin bold. Eagle 14 locations (all near GNP) are not shown.EAGLE NUMBERAND DATELOCATION(NORTH LATITUDEWEST LONGITUDE)km MOW;DEagle 01 (from the 1985 Hungry Horse nest)24 Apr 198615 km SSWCardston,AB, Canada (49ø05' 113023')100Eagle 08 (from the 1986 Logging Lake nest)5 May 1988b20 km NW Red Deer, AB, Canada (52ø23' 114ø00')27 May-6Jun b21 km E Edmonton, AB, Canada (53025' 113009')-(113)-528Eagle 06 (from the 1988 Logging Lake nest)18 Mar-1 Apr 1989aMissouriRiver,near Cascade,MT (47022' 111ø33')2 ApraHarwood Lak

National Park Service, Glacier National Park, West Glaci MT 59936 U.S.A. AgsTv, CT.- During 1985-95, we documented fledging, migration, and subsequent locations of juvenile bald eagles (Haliaeetus leucocephalus) from Glacier National Park (GNP),