j. RaptorRes. 35(2):91-97 ¸ 2001 The Raptor ResearchFoundation, Inc.

FORAGING HABITATS OF STELLER'S SEA-EAGLES DURING THE WINTERING SEASON IN HOKKAIDO, JAPAN

SAIKO SHIRAKI 1 GraduateSchool of Environmental Earth Science,Hokkaido University, Sapporo 060 0810Japan

A•ST}•½T.--Steller'sSea-Eagles (Haliaeetus pelagicus) winter mostlyin Hokkaido,Japan. To clarifythe tem- poral changesin foraginghabitats used by the eaglesthroughout the winteringseason, and factorsaffecting their choicesof foraginghabitats, I surveyednumbers of wintering eaglesat 71 sitesclassified into five foraging habitat types (river basins,river estuaries,lakes or inland bays,coasts, and refuse dumps) from November to April 1991-92, and temporal changesin the food resourceabundance at the major feeding sites.Most eagleswere observedin river basinsduring Novemberand Decemberand the number of eagles fluctuatedwith temporalchanges in the number of salmoncarcasses in the SyokotsuRiver. The eagles appeared to move among rivers accordingto the abundanceof availablesalmon. In mid-Februaryand earlyMarch, the eagleswere observedin varioushabitats but not at river basins.The distributionof eagles was affected by fishery activitieson coasts,in lakes,and on inland baysduring these periods.Estuaries, lakes,and inland baysmaintained open waterareas in the ice and appearedto be importantfeeding sites throughout the winter. On Furen Lake, the numbersof eaglesdid not fluctuate with temporal changes in the amount of food fisheriesdiscarded. It waspossible that eaglesstayed at Furen Lake evenwhen the abundance of availablesmall fish did not meet their food requirementsand indicate that there not cur- rently sufficient,suitable natural foraging habitats on the winteringgrounds in Hokkaido during severe winters to maintain the current population of Steller'sSea-Eagles. KEYWORDS: Steller'sSea-Eagle, Haliaeetus pelagicus; foraging habitat;, wint• fisher•y;Hokkaido.

Habitos de forrajeo de Haliaeetuspelagicus durante la estacionde invierno en Hokkaido,Jap6n P•SuM•.--Haliaeetuspelagicus pasa la mayoriadel inviernoen Hokkaido,Jap6n. Para clarificar los cambios temporalesen loshfibitos de forrajeoutilizados por las•tguilas a travesde la estaci6ninvernal y losfactores que afectanla selecci6nde losmismos, investigufi un nfimerode figuilasen 71 sitiosclasificados, en cinco tipos de habitats de forrajeo (cuencasde rios, estuarios,lagos, bahias internas, costasy vertederos de desechos)desde Noviembre hastaAbril 1991-92 y los cambiostemporales en la abundanciade comida de los principalessitios de alimentaci6n.La mayoria de las •tguilasfueron observadasen los vailesde los rios durante Noviembrey Diciembre,el nfimero de •tguilasfluctfio con cambiostemporales en el nfimero de restosde salmonen el rio Syokotsu.Las figuilas aparentemente se movilizaron entre losrios de acuerdo a la disponibilidaddel salm6n.A mediadosde Febreroy principiosde Marzo lasfiguilas fueron observadas en varios habitatsdistintos a los vailes de los rios. La distribuci6n de las •tguilasfurl afectada por las actividadespesqueras en las costas,en lagosyen las bahiasinternas durante estosperiodos. Los estuarios, lagosy bahiasinternas mantuvieron fireas abiertas de agua en el hielo, fueron sitiosimportantes de ali- mentaci6n durante el invierno. En el Iago Furen, los nfimerosde •tguilasno fluctuaron con los cambios temporalesen la cantidadde comidaque laspesqueras descartadas. Es posible que lasfiguilas se estuvieron en el Iago Furen a pesar que la abundancia de pequefiospeces no cumplia con los requerimientos alimenticioscomo tampocode que habia suficientehabitat apropiado para forrajeo en Hokkaido durante los fuertesinviernos como para mantener la poblaci6n de Haliaeetuspelagicus. [Traducci6n de C•sar Mfirquez]

The total number of Steller's Sea-Eagles(Hal- with the number of adults estimated at 5600 (del iaeetuspelagicus) in the world is estimatedat 7500 Hoyo et al. 1994). Becauseof the small population size, this eagle is listed as a vulnerable species • Presentaddress: Biology Department, Abiko Research (IUCN 1996). Laboratory,Central ResearchInstitute of Electric Power Steller's Sea-Eaglesbreed in the Lower Amur Industry, 1646 Abiko, Abiko-shi,Chiba-ken 270-1194, Ja- River, and in coastalregions along the western Be- pan. ring Sea, Kamchatka Peninsula, Okhotsk Sea, and

91 92 SHmArO VOL. 35, NO. 2 northern Sakhalin Island in northeastern Russia 143 ø E (Lobkov and Neufeldt 1986). After breeding, some eagles migrate southwardfor winter (Lobkov and Neufeldt 1986). Wintering areasoutside breeding areasinclude the South Primorskiregion, the Kuril Islands, Sakhalin Island, and the island of Hokkai- do, Japan (del Hoyo et al. 1994). There were 2200 Steller's Sea-Eagleswintering on Hokkaido in 1985 (Nakagawaet al. 1987), indicating that Hokkaido is an important wintering area. Eagles begin migration to Hokkaido by way of the SoyaCape, the northernmost tip of Hokkaido, in late October and depart Hokkaido in early March (Ito 1991). The distribution of wintering Steller's Sea-Eaglesin Hokkaido in late November 44' N is determined by the abundance of chum salmon (Oncorhynchushera) in rivers (Ueta et al. 1999). In February, most eagles have been recorded on the Rausu coast in Nemuro Strait and in lakes and in- land bays in the eastern and northern parts of Hokkaido (Working Group for White-tailed Eagles and Steller's Sea-Eagles1996). Along the Rausu coast, they gather to eat walleye pollock (Theragra [] Lake or inland bay 50 km chalcogramma)that have fallen out of gill nets dur- ß Refuse dump I ing fishery activitiesand small fish discardedfrom 145 ø E ice fisheries (nets under the ice) on frozen lakes Figure 1. Map of studyarea and 71 censussites indicat- and inland bays.This suggeststhat, in Hokkaido, ed by each foraging habitat type in northern and eastern salmon are the major food resource during the parts of Hokkaido, Japan. early wintering period, and subsequentlyfish de- rived from fishery activitiesbecome an important food source. November in the northern part, 11-18 December, 12-19 February, 28 February-9 March, 25-28 March and 1-2 It is important for the conservation of the win- April, and 9-16 April. 1 counted eaglesfrom each site as tering population of Steller's Sea-Eagleto clarify far as I could see from sunrise to 1500 H when weather the statusof foraging habitats.There have been no did not interfere with observations. reports on the use of foraging habitatsthroughout White-tailed Eagles (H. albicilla)also winter with Stell- the wintering season.Therefore, the objectivesof er's Sea-Eaglesin Hokkaido, so I recorded eaglesas one of three types: Steller's Sea-Eagles,White-tailed Eagles, this studywere to clarify the temporal changesin and unidentified sea eagles.For the purpose of analyses, foraging habitats used by Steller's Sea-Eagles unidentified eagles at each site were split into Steller's throughout the wintering seasonand to examine Sea-Eaglesand White-tailed Eagles in proportion to the the factorsaffecting the use of foraging habitats. number of identified birds of each species.At lake and inland bay sites,I estimated the percentage of the area STUDY AREA AND METHODS surveyedthat was frozen. The number of Steller's Sea-Eaglesobserved on the coastalsites of Rausu (Fig. 1), and other coastalsites dur- Steller's Sea-Eagleswere censused from November ing mid-February and early March in 1992 wascompared 1991-April 1992 at 71 fixed sitesestablished in the north- by a Mann-Whitney [3test. In some lakes and inland bays, ern and easternparts of Hokkaido (Fig. 1). Selectionof commercial fisheries were operational concurrent with these siteswas based on the viewsthey provided and ac- the presence of wintering Steller's Sea-Eagles.To com- cessibilityof the observationpoints. The siteswere clas- pare eagle use at sitesused for commercial fisheriesver- sified into five foraging habitat types:river estuaries(N susnonfishery sitesfrom mid-February to early April in = 21, 0-500 m from the river mouth), river basins (N = 1992, tests for differences between areas were made with 9, upper part of the estuary), coast (N = 19), lakes or Mann-Whitney [3tests. inland bays (N = 19), and refuse dumps including gar- I counted eagles and salmon carcassesnearly once a bage dumps (N = 3). The censuswas divided into six week from November to early December, 1994 along the periods: 4-10 November in the eastern part and 27-30 Syokotsu River (main stream and a tributary), which JUNE 2001 STELLER'SSEA-EAGLE FORAGING HABITAT 93

450- observed at other sites. This indicated that the 400• preference of eagles for a feeding site could not •5o• alwaysbe explained by habitat type alone. 300- In the first two periods, November and mid-De- 250- cember, nearly all eagleswere observed in river ba- sins.On the SyokotsuRiver, there was a significant 2oo '.. : correlation between the number of salmon car- 150- .. cassesand the number of Steller's Sea-Eaglesfrom 100- 10 November-8 December (Kendall rank-order 50• correlation test, x = 0.90, P = 0.028) (Fig. 4). Be- cause few eagles were observed in other habitats Nov. mid-Dec, mid-Feb,early Mar. lateMar. mid-Apr, during these periods, the eaglesappeared to stay

Survey period at, or leave rivers depending on the abundance of salmon carcasses.After the mid-December period, Figure 2. Fluctuation in the number of Steller's Sea-Ea- eaglesdisappeared from river basinsand were ob- glescounted at 71 sitesin the easternand northern parts served in various other habitats (Fig. 3). During of Hokkaido, November 1991-April 1992. mid-February and early March, many eagleswere observed at sites along the Rausu coast. In early empties into the Sea of Okhotsk in northeastern Hok- March, eagles were found at significantly higher kaido (Fig. 1). Eagleswere counted froln the mouth to densitiesalong the Rausu coast than at other sites a point 17 km upstream. Sahnon carcasses,primarily on the coast (Mann-Whitney U-test,Z = -2.15, P chum salmon (Onc0rhynchushera), were counted on shal- = 0.032), but no significantdifference was found lowsand sand banks at eight fixed 500-m-longzones by between these sitesin mid-February (Z = -1.24, P walking along the river. The relationship between the number of sahnoncarcasses and occurrenceof eagleswas = 0.22). Steller's Sea-Eagleswere observed at re- examined by a Kendall rank-order correlation test. fuse dumpsfrom mid-Februaryto mid-April eating At Furen Lake, one of the major wintering placesfor garbage (Fig. 3). In particular, many eagles were eagles,in easternHokkaido (Fig. 1), the ice fishery usu- observedat one refusedump during mid-February ally starts in late December after freeze-up, and ceases around the beginning of April when the ice begins to and early March. melt. I counted Steller's Sea-Eagles,White-tailed Eagles, Eagleswere observed in lakes, inland bays, and and unidentified eagles on the western part of Furen river estuariesthroughout the censusperiod (Fig. Lake during the winters of 1994-95 and 1997. Most of 3). In mid-February,when ice fisherieswere pres- the small fish from the ice fishery operations were ent on lakes and inland baysthat were nearly fro- dumped directly onto the ice. To estimate the total mass of smallfish discardedin this area, I measuredthe weight zen over, eaglesgathered more at fishery sitesand of all the fish that were caught with a fishing net and they fed upon small fish, such as Myoxocephalusstel- dumped on the ice from 15-20 nets in each surveype- leri,Pholidapus dybowskii, and Pleuronectespinnifascza- riod. I also counted the nets within the censused area. tus that had been discarded by fishermen (Z = These surveyswere conducted six times from late Decem- ber to early March in 1994-95, and three times from late -2.32, P = 0.020) (Fig. 5). After mid-February,the January to late Februaryin 1997. The total massof small surfacesof lakes and inland baysgradually melted fish per week was calculatedas: (mean weight of fish in and subsequentlythe activitiesof the ice fisheries a net per day) X (total number of nets in the surveyed decreased.At these siteswhere there were open area) X (number of daysof fisheryconducted in a week). water areasin the ice, I sometimesobserved eagles The relationshipbetween the temporal changein the to- tal massof smallfish and the number of eaglesobserved trying to catch fish while perching on the ice was examined by a Kendall rank-order correlation test. around open water.In early March at about 70% of the studysites, water surfaceswere incompletely RESULTS coveredby ice while, at other sites,they were com- In the surveyed area, there was a minimum of pletely coveredwith ice. During this period, there 56 Steller'sSea-Eagles during each observationpe- were no differences in the number of eagles be- riod, with numberspeaking in mid-Februaryat 405 tween the fishery and nonfishery sites (Z = - 1.30, eagles (Fig. 2). During the surveyedperiods, the P = 0.19) (Fig. 5). In late March, water surfaces use of foraging habitat types by eagles changed were partially coveredwith ice at all but one of the (Fig. 3). However,within a habitat type, many ea- sitesand eaglesgathered more at nonfishery sites gles gathered at some sites,while no eagleswere than at fishery sites (Z = -2.02, P = 0.043) (Fig. 94 SHIRAKI VO•,. 35, NO. 2

5). In mid-April, one site was about 40% covered with ice, while other sites did not have ice. There 15]o RiverN=9basin 10 wasno difference in the number of eaglesbetween the fishery and nonfishery sites,although most ea- gleswere counted at the siteswith partial ice cover (Z = -1.12, P = 0.27) (Fig. 5). Thus, theseresults indicated that frozen lakes and inland bayswhich are partly thawed could be good feeding sitesun- der natural conditions for eagles. Similarly, as 15' River estuary many estuarieshad an open area throughout the N=21 winter, eaglescould capture prey. 10' There were no significantrelationships between the mass of discarded fish and the number of ea- o gles in 1994-95 (Kendall rank-order correlation test, ß = 0.20, P = 0.57) or in 1997 (• = -0.33, P = 0.60) (Fig. 6). There were two possibleexpla- nations for this result. There was enough smallfish 15 Lake or for the eaglesthroughout the wintering period on o Inland bay Furen Lake or the eaglesstayed at Furen Lake even when food was scarce.To evaluate these two expla- nations, I calculated the food requirement of ea- o gles (including White-tailed Eagles) eating small 1• N=19 fish on this lake as follows: the mass of small fish per eagle was lowest in late February 1995, when 330 Steller's Sea-Eaglesand White-tailed Eagles 04., ...... were recorded in total. Average daily food con- 15' o sumptionby White-tailed Eagleshas been estimat- Coast ed to be 514 g (male = 456 g, female = 571 g; o N=19 10' o Love 1979). If an eagle ate 514 g of fish/d at Furen Lake, 330 eagleswould have eaten 1187 kg/wk, which was less than the total mass of discarded fish (2161 kg/wk) in late February 1995. However, competitorsfor fish included gulls, Larus schistisa- gus,L. argentatus,L. glaucescens,and L. hyperboreus, which were the largestconsumers of discardedfish 24- ß on Furen Lake (Lobkov unpubl. data), as well as 20- Refuse dump Black Kite (Milvus migrans)and crows (Corvusma- 16- N=3 crorhynchosand C. corone).These competitorsusu- 12- (a ß ß Censussite) ally approachedand ate discardedfish soonerthan sea eagles,and the eaglesfed on the rest. There- 8 fore, it was possiblethat there was an insufficient 4 amount of small fish for the eaglesin late February 0 ' and the secondexplanation applied. Nov.mid- mid- early late mid- Dec. Feb. Mar. Mar. Apr. Survey period Fzgure 3. Box plot of the number of Steller's Sea-Ea- gles/km2 in each foraging habitat type counted in the tomsindicate number of Steller'sSea-Eagles/kin e within eastern and northern parts of Hokkaido, November 25% of the data. Whiskersindicate the range of 90% of 1991-April 1992. Boxescover the middle 50% of the data the data. Open circlesrepresent outlying numbers.N = and center lines indicatemedians. Tops of boxesindicate number of censussites. Sample size at the refusedump number of eagles/km2 within 75% of the data and bot- was not enough to make a box plot. JUNE 2001 STELLER'SSEA-EAGLE FORAGING HABITAT 95

12 20 160001994-95 •10] •, 14000 ,ooo 400• lO'• • 8000d 1-300• 6000 '• 4 E o 200 =E 5 •' • 4000 z 100 2000 Z ß-' .z 0 late early late early late early 10 Nov. 17 Nov. 25 Nov. 30 Nov. 8Dec. Dec. Jan. Jan. Feb. Feb. Mar. Survey date 16000- • Salmoncarcass • Steller'sSea Eagle .-.14000~ 600 Figure 4. Relationshipbetween the numbers of Steller's • 12000; •500• Sea-Eaglesand salmon carcassesat the SyokotsuRiver •.... k400_•o• o•10000 from 10 November-8 December 1994. 300 • • 8000 DISCUSSION 200• 4000 ß z 100 The movementsand distributionof Bald Eagles 2000 (Haliaeetusleucocephalus) are influenced by food • •' 0 availability during winter (Southern 1964, Steen- I•e mid- late hof et al. 1980, Grubb 1984, Griffin and Baskett Jan. Feb. Feb. 1985, Isaacsand Anthony 1987). My studyand the Survey period -•- Numberof Steller'sSea Eagle mid-Feb.* 6 lateMar.* • Massof fish (kg / week)

Figure 6. Temporal fluctuations of number of Steller's Sea-Eaglesand the massof discarded fish in the western

3 part of Furen Lake in the wintering seasonsof 1994-95 and 1997.

1

o studyofUeta et al. (1999) have shownthat Steller's Fishery Non-fishery Fishery Non-fishery Sea-Eaglesmove among river basinsaccording to N=13 N=6 N=13 N=6 changes in the abundance of salmon carcasses. 6' Some Steller's Sea-Eagles tracked by satellite eadyMar. mid-Apr. • 5- Z 5- moved from their breeding areas in northern Sa-

4- 4- khalin, the nearby continental seaboards,and the Amur River to Hokkaidovia the SoyaCape during 3- 3- late fall (Ueta et al. 2000, McGradyunpubl. data). 2- 2- After a short stay in Hokkaido, these eaglesmi- I 1 grated to the Kuril Islands (Fig. 1), where numer- ous salmon were available, and returned to Hok- 0 0 Fishery Non-fishery kaido in January and February (Ueta et al. 2000, N=14 N=5 N=11 N=8 McGradyunpubl. data). Their return waslikely re- lated to the number of available salmon which de- Figure 5. Mean number of Steller'sSea-Eagles/kin 2 at commercialfishery and nonfisherysites in the lake and creasedin the Kuril Islands.This finding suggests inland bay habitatsin 1992. Mean is shownwith standard that, across the wintering range, movements of deviation (thin vertical bars). *Significantlydifferent Steller's Sea-Eagleare affected by the distribution (Mann-Whitney/•test). of salmon during the early wintering season. 96 SHmAK• VOL. 35, NO. 2

The number of Steller's Sea-Eaglesfluctuated in lets has been introduced by the Japanesegovern- responseto the abundance of salmon carcassesin ment. If the use of lead shot is not restricted, lead the river basin. Meanwhile, the number of eagles poisoningmight causea decline in the population did not correlate with the mass of small fish in Fu- (Kim et al. 1999, Iwata et al. 2000, Ueta and Mas- ten Lake. The availability for Bald Eagles is often terov 2000). The Environmental Agency of Japan highly variable in time and space,resulting in fre- announced the banning of lead bullet use in Hok- quent movements in search of food (Stalinaster kaido beginning in the fall of 2000. and Gessaman 1984), while more available prey In this study,lakes, inland bays, and river estu- probably allows eaglesto stayin some areas rather aries with areas of open water could be feeding than move to others (Isaacs et al. 1996). In addi- placesunder natural conditionsduring severewin- tion, Bald Eaglesare able to withstandlong periods ters. Kuril Lake in south Kamchatka, Russia, is one of food deprivation (Stalmaster and Gessaman of the largest wintering areas for Steller's Sea-Ea- 1984). BecauseSteller's Sea-Eaglesremained in Fu- gles, and they stayto feed on salmon from October ten Lake in spite of apparent food shortages,I con- to March (Ladigin et al. 1991). A similar situation cluded that the food shortage was tolerable for occursin Hokkaido, where some eaglesoverwinter them and that stayingat Furen Lake was more ad- at a few rivers by feeding on salmon carcassesthat vantageousthan moving to another foraging hab- remained from fall salmon runs (Shiraki 1996). itat. It may be that the eaglesdid not have other Thus, salmon could be one of the important food feeding placeswith better food availability. resourcesfor eagles late in the fall season.How- Recently, Steller's Sea-Eagleshave begun to ap- ever, in many rivers in Hokkaido, most of the salm- pear in mountainousareas to feed on deer (Cervus on are captured in the lower part of riversduring n•ppon)carrion abandoned by hunters (Kurosawa the fall seasonto collect eggs for artificial propa- 1998). Since the mid-1990s, with the decrease in gation (Shiraki 1996). Therefore, during severe the commercial catch of walleyepollock along the winters, salmon carcassesavailable to eagles are Rausucoast, Steller's Sea-Eagles have tended to dis- very scarcein most of the rivers.In addition, eagles perse from the Rausu region (Working Group for require shallowsand sand banks for feeding, and White-tailed Eaglesand Steller's Sea-Eagles1996). suitable forest areas for perch sites and shelter. Concurrently, because the number of deer has Most rivers in Hokkaido are unsuitable habitats for greatly increasedand more deer have been hunted eaglesowing to alternationsof river wallsand river in order to lessen agriculture damage, more deer beds, and the cutting of riverside forests (Shiraki carrion are being made availableto eagles (Kuro- 1996). Steller's Sea-Eagles'winter movementsare sawa2000). Thus, Steller'sSea-Eagles may begin to associated with the fluctuation of food resources gather in mountain areas which have become over the wintering range. Therefore, it is desirable more profitable foraging habitats than fisheries in to conservewintering habitats not just in Hokkai- recent years. Eagles have tended to change their do, but over the entire wintering range of the spe- feeding areas in recent years among areas where cies. human activitiessupply food during severewinter ACKNOWLEDGMENTS seasons.This fact suggeststhat suitable,natural for- aging areas during severewinter are insufficient to I am grateful to S. Tsuyuzakiand Y. Fujimaki for mak- maintain the current population of Steller's Sea- ing comments on an earlier draft of this manuscript. I thank M. Miller, D. Garcelon, and G.R. Bortolotti for im- Eagles. proving this manuscript,H. Fukuda for supportand use- in addition, these anthropogenic food sources ful suggestionson this study,and E.G. Lobkov,and MJ. may not be ideal for maintaining populations due, McGrady for providingunpublished data. I alsothank H. not only to their lack of stabilitybut also for their Nakagawa,M. Tazawa,T. Takeda, and N. Aoki for their potential for containing pollutants.Whole and par- support on field surveysand the fishermen of the Bekkm Fishery CooperativeAssociation for their cooperationin tial carcassesof deer shot by hunters are left in the the surveyson Furen Lake. This studywas partially fund- field (Kim et al. 1999, Iwata et al. 2000), and lead ed by the World Wildlife Foundation of Japan. fragments embedded in tissue are often ingested LITERATURE CITED by eaglesduring and after the hunting season(Iwa- ta et al. 2000). Forty six eagleswere found to have DEL HOYO,J., A. ELLIOTœ,AND J. SARGATAL[EDs]. 1994 died from lead poisoningduring 1997-99 (Kuro- Handbook of the birds of the world. Vol. 2. Lynx Ed- sawa2000). No regulation on the use of lead bul- icions, Barcelona, Spain. JUNE 2001 STELLER'SSEA-EAGLE FORAGING HABITAT 97

GRIFFIN,C.R. ANO T.S. BASKETr.1985. Food availability Lom;ov, E.G. AND I.A. NEUFELDF. 1986. Distribution and and winter range sizes of immature and adult Bald biology of the Steller's Sea-EagleHaliaeetus pelag•cus Eagles.J. Wildl. Manage.49:592-594. pelagicus(Pallas). Proc. Zool. Inst. Acad. Sci. 150:107- GRUBB,T.G. 1984. Winter activityof Bald Eagles(Haliaee- 146. (In Russian) tus leucocephalus)at Navajo Lake, New Mexico. South- LOVE,J.A. 1979. Daily food intake of captiveWhite-tailed west. Nat. 29:335-341. Eagles.Bird Study26:64-66. IsMcs, F.B. AND R.G. ANTHONY. 1987. Abundance, for- NAKAGAWA,H., E.G. Lorn;or, AND Y. FUJ•MAIiI.1987. Win- aging, and roosting of Bald Eagleswintering in the ter censuseson Haliaeetuspelagicus in the Kamchatka Harney Basin, Oregon. NorthwestSci. 61:114-121. and northern Japan in 1985. Strix6:14-19. --, --, g.v. HEYDEN, C.D. MILLER, AND W. SHIP,Ard, S. 1996. Distributions of Steller's Sea and White- WEATHERFORD.1996. Habits of Bald Eagleswintering tailed Eagles in the rivers of Hokkaido. Pages 15-27 along the upper John Day River, Oregon. Northwest in Survey of the status and habitat conditions of Sci. 70:1-9. threatened species,1995. Environment Agency, To- ITO, M. 1991. Migration of Steller'sSea-Eagles and White- kyo,Japan. (In Japanesewith Englishsummary) tailed Eaglesin SoyaCape. Pages45-49 in The Survey SOUTHERN, W.E. 1964. Additional observations on winter of the Special Birds. Wild Bird Society of Japan, To- Bald Eagle populations:including remarks on biote- kyo, Japan. (In Japanese) lemetry techniques and immature plumages. With'on IUCN. 1996. IUCN red list of threatened animals. IUCN, Bull. 76:121-137. Gland, Switzerland. STALMASTER,M.V. ANDJ.A. GESSAMAN.1984. Ecological IWATA, H., M. WATANABE,E-Y. IZdM,R. GOTOH, G. YASUN- energetics and foraging behavior of overwintering AGA, S. TANABE,Y. MASUDA,AND S. FUJITA.2000. Con- Bald Eagles.Ecol. Monogr. 54:407-428. tamination by chlorinated hydrocarbonsand lead in STEENHOF, K., S.S. BERLINGER, AND L.H. FREDRICKSON Steller's Sea-Eagleand White-tailed Eagle from Hok- 1980. Habitat use by wintering Bald Eagles in South kaido, Japan. Pages 96-106 in M. Ueta and M.J. Dakota.J. Wildl. Manage.44:798-805. McGrady [EDS.], First Symposium on Steller's and UETA,n., n. KOITA,AND K. FUKUI.1999. The relationship White-tailed Eaglesin EastAsia. Wild Bird Societyof between the autumn distributions of salmon and of Japan, Tokyo,Japan. Steller'sand White-tailed Eaglesin Hokkaido,Japan KIM, E-Y., R. GOTOH, H. IWATA, Y. MASUDA, S. TANABE, Strix17:25-29. (In Japanesewith Englishsummary) AND S. FUJITA.1999. Preliminary survey of lead poi- , F. SATO, H. NAKAGAWA,AND N. MITA. 2000. Mi- soning of Steller'sSea-Eagle (Haliaeetus pelagicus) and gration routes and differences of migration schedule White-tailed Eagle (Haliaeetusalbicilla) in Hokkaido, between adult and young Steller's Sea-EaglesHahaee- Japan. Environ. Toxicol.Chem. 18:448-451. tuspelagicus. Ibis 142:35-39. KUROSAWA,N. 1998. Lead poisoning of Steller's Sea-Ea- -- ANDV. MtASTEROV.2000. Estimation by a computer gles and White-tailed Eaglesin Hokkaido. J. Hohhaido simulationof population trend of Steller'sSea-Eagles Vet.Med. Assoc.42:336-338. (In Japanese) Pages111-116 in M. Ueta and M.J. McGrady --. 2000. Lead poisoning in Steller's Sea-Eaglesand First symposiumon Steller's and White-tailed Eagles White-tailed Eagles. Pages 107-109 in M. Ueta and in EastAsia. Wild Bird Societyof Japan, Tokyo,Japan M.J. McGrady [EDS.],First symposiumon Steller'sand WORKING GROUP FOR WHITE-TAILED EAGLES AND STELLER'S White-tailed Eagles in East Asia. Wild Bird Society of SEA-EAGI,ES.1996. Wintering statusof Steller's Sea-Ea- Japan, Tokyo,Japan. glesand White-tailed Eaglesin northern Japan. Pages LAInGIN, A.V., E.G. LOBKOV, AND O.N. LAI)IG•NA. 1991. 1-9 in Survey of the statusand habitat conditions of The hugest wintering of White-shouldered Eagle at threatened species.Environment Agency, Tokyo, Ja- Kuril Lake (South Kamchatka). Byull.Mosh. Ova Ispyt. pan. (In Japanesewith English summary) Prir. Otd.Biol. 96:48-57. (In Russianwith Englishsum- mary) Received30 September 1999; accepted11 February 2001