First Symposium on Steller’s and White-tailed Sea Eagles in East Asia pp. 83-90, 2000
UETA, M. & MCGRADY, M.J. (eds) Wild Bird Society of Japan, Tokyo Japan

Migration and wintering of juvenile and immature Steller’s Sea Eagles
Michael J. MCGRADY1*, Mutsuyuki UETA2, Eugene POTAPOV3, Irina UTEKHINA4,
Vladimir B. MASTEROV5, Mark FULLER1,6, William S. SEEGAR7,
Alexander LADYGUIN8, Eugene G. LOBKOV9 & Vladimir B. ZYKOV10
1. Raptor Research Center, Boise State University, 1910 University Drive, Boise, Idaho 83725-1516, USA.
2. Research Center, Wild Bird Society of Japan, 2-35-2 Minamidaira, Hino Tokyo 191-0061, Japan.
3. Academy of Sciences, 685000 Magadan, Russia.
4. Magadan Nature Reserve, Portovaya st., 8, 685000 Magadan, Russia.
5. Dep. Vertebrate Zoology, Laboratory of Ornithology, Moscow State University, 199899 Moscow, Russia.
6. USGS Snake River Field Station, 970 Lusk St. Boise, Idaho 83706, USA.
7. Edgewood Research Development and Engineering Center, Aberdeen Proving Ground, Maryland, USA.
8. Foundation for Agrarian Development Research, Science Park of MSU, 119899 Moscow, Russia.
9. Kronotzky State Biosphere Reserve, 684010 Elizovo, Kamchatka, Russia.
10. Information Research Center "Fauna", Komsomolskaia str.241a, 14, 693023 Yuzhno-Sakhalinsk, Russia.

Abstract. Twenty-nine nestling Steller’s Sea Eagles Haliaeetus pelagicus were fitted with satellitereceived transmitters (PTTs) in the summers of 1997 and 1998. Twenty-four provided data useful inunderstanding post-fledging movements, 12 from Magadan, 7 from Amur, four from Kamchatka,
and one from Sakhalin. At this time (27 January 1999), we are still receiving information from six
birds. Fledging occurred in August and early September. At least 20 fledglings moved to pre-migrationsites for 1-4 weeks. This behavior was most obvious for birds whose natal ranges were coastal.
Eagles raised on large rivers and lakes tended to wander along rivers prior to the onset of a definite
migratory push. Nineteen birds were followed south, 16 made it to wintering areas. Eagles took 5-116
days to reach their initial wintering destinations. Migration rate averaged 51.3 km/day (SD = 56.0).
Most birds from Magadan and Amur migrated down the western edge of the Okotsk Sea, and birds
reared in Kamchatka eventually moved onto the Kuril Islands. Two birds were tracked from fledging
into their second autumn migration. They moved northward from the wintering grounds in the second
and third week of April. Summering areas were south of natal areas, and both had early and latesummering areas.

INTRODUCTION
The Steller’s Sea Eagle Haliaeetus pelagicus occupies a limited breeding range along theseacoasts and on islands and rivers of eastern Siberia from Koryakland south to northern* Present address: Institute for Wildlife Studies, P.O.Box 1104, Arcata, CA 95521, USA.
e-mail: mikemcgrady@hotmail.com

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Table 1. Details of PTTs fitted to Steller's Sea Eagle nestlings in 1997 and 1998.
Year
Region1997 Magadan
Kamchatka
Amur
1998 Kamchatka
Amur
Sakhalin

No. of PTTs
4
10
1
3
3
2
4
1
1

Manufacturer
Duty cycle
Microwave 8 hrs on 48 hrs off
Toyocom 6 hrs on 12 hrs off
Toyocom 6 hrs on 48 hrs off
Toyocom 6 hrs on 12 hrs off
Toyocom
Toyocom
Toyocom
Toyocom
Toyocom

5 hrs on 19 hrs off
6 hrs on 42 hrs off
5 hrs on 19 hrs off
6 hrs on 48 hrs off
5 hrs on 19 hrs off

Life expectancy
1.5 yrs
6 months
1 year6 months
9 months
1 year9 months
1 year9 months

Korea. Part of the population over-winters in the breeding range, concentrating around ice-free
portions of lakes, rivers and the sea (Nakagawa et al. 1987, Lobkov & Neufeldt 1986). Others
move south to Hokkaido, the Kuril Islands, Korea, and the coast of the Russian mainland(Babenko et al. 1988, Lobkov 1988, Nakagawa & Fujimaki 1988).
Details of post-fledging dispersal and migration of Haliaeetus eagles have been studied
elsewhere using conventional (e.g. Hunt et al. 1992, McClelland et al. 1996) and satellite
telemetry (e.g. Grubb et al. 1994, Ueta et al. 1998). Steller’s Sea Eagles movements have beenstudied using direct observations (WGWS 1996), color marks (Ueta and Utekhina unpubl.
data), and satellite-received transmitters (PTTs) (Meyburg & Lobkov 1994, Ueta et al. 2000).
The use of radio tracking via satellites is particularly appropriate given the remoteness of areasin which the Steller’s Sea Eagle lives (Fuller et al. 1995). We report upon the results oftracking Steller’s Sea Eagle nestlings fitted with PTTs in Magadan, Kabarovsk, Amur, andSakhalin Regions and on the Kamchatka Peninsula of Russia.

MATERIALS AND METHODS
Two types of PTT were used, Toyocom (25) and Microwave (4). Some PTTs were
programmed for longer life (and a slower rate of data collection). Table 1 summarizes PTT
characteristics. All transmitters weighed about 65g, and were attached in backpack fashionusing Teflon ribbon (e.g. Dunstan 1972), incorporating a sewn link at the breast. The linkshould degrade after some time, allowing the backpack to fall free of the bird. Two eagles
were tracked for more than 16 months. Data on these birds included location estimatescollected during the first spring migration, the second summer and the second autumn
migration.
When analyzing movement, we used only ARGOS location classes 1, 2 or 3. Location
classes 1, 2 and 3 mean that 68% of location estimates would lie within a radius of 1 km, 350
m and 150m, respectively.

85
Table 2. Summary of migration by juvenile Steller's Sea Eagles from Russia in 1997-1998.
PTT ID

Initiation of No. of locations Date arrived on Duration ofkm
Rate
Degrees of Latitude tomigration
on migration wintering grounds migration traveled (km/day) Wintering grounds

1997
11986 – 10 Oct.
16
15 Jan.
97
2774
28.6
11987* – 13 Oct.
414 Nov.
31
2216
71.5
11988 – 25 Oct.
1
15 Nov.+
21
2500
129.0
11989 – 27 Oct.
108 Dec.
42
2550
60.7
23372 – 24 Sep.
69
05 Dec.
72
2600
36.1
23374 – 1 Nov.
97
20 Nov.+
5
1140
228.0
28509 – 2 Oct.
51
20 Nov.
49
2408
49.1
28510 – 15 Oct.
38
16 Nov.+
32
1450
45.3
28512 – 4 Oct.
48
14 Jan.
97
200
2.1
28513* – 19 Oct.
25
09 Dec.+
46
2344
50.9
1998
04131 – 26 Sep.
28
22 Nov.
57781
13.7
06749 – 25 Oct.
83
04 Jan.+71407
5.706755 – 14 Oct.
006 Nov.+
23
260
11.3
06762 – 18 Aug.
4
08 Nov.
82
1467
17.9
07018# – 24 Sep.
9
04 Oct.
11135
12.3
07101 – 4 Oct.
11
15 Nov.+
42
1288
30.7
07102 – 5 Nov.
69
14 Jan.+
70
1698
24.3
07317 – 6 Dec.
29
28 Dec.
22475
21.6*Left on migration from natal area, no pre-migration staging area noted (11987, 28513).
+
More than one wintering area noted (11988, 23374, 28510, 28513, 06749, 06755, 07101, 07102).
#
Wintering area north of natal area (7018).

16.3
14.6
17.0
16.0
17.0
6.2
14.0
6.6
1.0
13.0
7.0
2.8
4.0
1.9
0.5
7.7
9.8
3.4

RESULTS
Twenty-nine, nestling Steller’s Sea Eagles were fitted with PTTs in the summers of1997 and 1998. Twenty-four provided data useful in understanding post-fledging movements,
twelve from Magadan, 7 from Amur, 4 from Kamchatka and 1 from Sakhalin. We are still (27January, 1999) receiving information from six birds.
Fledging to Dispersal
Fledging occurred in August and early September for most eagles. Nestling dispersal(when the eagle moved permanently more than 5 km from the nest site) occurred 9 September
to 6 December (N = 24). Twenty-two nestlings dispersed 14 September - 21 October. Dates ofdispersal did not differ between years or regions.
Pre-migration and Migration
At least 20 fledglings moved to pre-migration sites for 1-4 weeks. This behavior was
most obvious for birds whose nesting sites were coastal. Pre-migration sites were on thelower reaches of rivers and might be areas where dead (post-spawning) salmon are found inabundance. Eagles raised on large rivers and lakes tended to wander along rivers prior to theonset of a definite migratory push.
Nineteen birds were tracked on southward migration during their first autumn (Fig. 1).

86

Fig. 1. Autumn migration routes of Steller's Sea Eagles from Magadan, Amur, Sakhalin and Kamchatka.

Table 2 summarizes the data. Birds initiated migration between August 18 and November 15.
Birds marked in 1997 migrated earlier than those marked in 1998. Migration occurred between
August 18 and January 14. All but one followed established migration routes. The pace of
migration varied considerably. Birds took 5 to 116 days to reach their initial wintering
destinations. Migration rate averaged 51.3 km/day (SD = 56.0). Most birds from Magadan andAmur migrated down the western edge of the Okhotsk Sea, and birds reared in Kamchatka
moved down the Kuril Island chain. The eagle whose migration patterns was ‘atypical’ (ID23374) was marked in Magadan region. It made an initial move west, then turned east, andmigrated to the Kamchatka Peninsula. Only one location between the breeding and wintering
grounds was estimated for this bird. This was of relatively low quality, but was located in the
middle of the sea, and suggests that the bird may have made a sea crossing. The shortest
crossing would be about 730 km.
For two birds, no wintering grounds could be identified. Either they did not settle in one
wintering area or the transmitter stopped working before this occurred. Mortality wasconfirmed for one bird and strongly suspected for another. ID 11987 was collected in China

87
Table 3. Summary of second summer movements by Steller's Sea Eagles.
ID
11986
11988

Date of N.
Migration
10 Apr
26 AprDate of
Arrival25 Jun24 JunDate of
Departure
17 Jul10 JulMedian Location
55.069N, 137.903W
53.894N, 142.346W

Date of
Arrival01 Aug
25 AugDate of
Departure
10 Sep24 Sepwith a broken wing (apparently from hitting electricity lines) on 10 November in the Xiang Hai
Nature Reserve. It died in captivity on 30 November. ID 28512 probably died on the Okhota
River. The pattern of location estimates suggests that this bird survived until 5 January at least.
It was last received on 25 January.
Wintering areas
Seventeen birds were followed through the autumn to relatively well-defined areas
where they spent > 2 weeks during the winter. By and large these were located on Hokkaido,
Sakhalin and the Kuril Islands. In winter 1997-1998, six birds used only one area, and four
used up to three distinct wintering areas. One eagle tagged in 1997 wintered on the Kamchatka
peninsula. Data gathering for 1998-1999 is not yet complete.
Northward migration, second summer and second autumn migration
Two birds, IDs 11986 and 11988, were tracked from fledging into the second autumn
migration. They moved northward from the wintering grounds in the second and third week ofApril, respectively. Summering areas were south of their natal areas. Both birds had early andlate summering areas. Median location estimates for IDs 11986 and 11988 in their earlysummering areas were 4.2 and 5.6 degrees south of their respective natal areas, and 12 and 10.5
degrees N of their respective wintering areas. Late summering areas were 2.3 degrees south ofnests and 14 degrees N of wintering area for ID 11986 and 5.0 and 11.2 degrees for ID
11988. IDs 11986 and 11988 initiated their second autumn migration on 10 and 24 September,respectively. Table 3 summarizes second summer movements by IDs 11986 and 11988.

DISCUSSION
Because location estimates calculated by the ARGOS system are of variable accuracy
gross movements can be interpreted with more confidence than small ones. There are anumber of limitations to PTT data, and sources of potential error in location estimates.
Additionally, some behaviors (like staging by eagles) might not be documented because thePTT duty cycles may not be appropriate. Because high quality data are only a proportion of all
location estimates, small sample size is often encountered. Because we excluded lower quality
data, the dates of movement we report are not necessarily precise, and should be interpreted as
accurate to within ± 2 duty cycles.
Food supply plays a large part in determining whether birds migrate, and where they

88
spend the non-breeding period (Newton 1979). We estimate that dispersal from natal areas
could have occurred as early as 2 weeks or as late as 15 weeks post-fledging and was probably
linked to declining prey availability (decreased numbers of prey or increase in ice cover).
Dispersal of a nestling chick in Kamchatka from another study occurred on 16 October(Meyburg & Lobkov 1994), within the range of dates over which the birds we studied
dispersed. The nestling whose natal area was furthest south (Sakhalin) initially moved north.
Presumably, this is because food was available to the north, and early winter weather was not
as harsh as in other areas where eagles were radio-tagged. Dispersal in Bald Eagles H.
leucocephalus coincides with declines in prey availability, and may be related to physicalcondition of the fledgling (Wood et al. 1998), and Bald Eagles breeding in southerly parts of
their range, migrate northward after nesting (Hunt et al. 1992).
Because of the duty cycles to which the PTTs operated, we may not have documented
stopovers for all birds that staged. When staging occurred on rivers, these were in areas
located somewhat inland where the river was not affected by tides, and where the speed andclarity of the water was relatively high appeared to be used.
Although we saw no significant variation in the timing of migration between regions,
within-year sample size was low. However, eagles reared in areas where ice forms earlier inthe year migrated earlier. Southward migration by Steller’s Sea Eagles marked in Kamchatka
followed the route used by a nestling eagle tagged with a PTT in 1991 (Meyburg & Lobkov
1994) and adult White-tailed Sea Eagles H. albicilla in 1995 (Ueta et al. 1998). Further, thebehavior of ID 23374 suggests that not all birds wintering in Kamchatka are from there.
Migration routes used by the eagles tracked for more than one migration (IDs 11986 and
11988) were similar, and agree with data collected by Ueta et al. (2000).
Distribution of Steller’s Sea Eagles in autumn and winter in Hokkaido has been linked to
distribution of prey and prey availability. Fish species of importance include salmon
Oncorhynchos keta (Ueta & Kiota 1996, Shiraki 1996, Ueta et al. 1999), Walleye Pollock
Theragra chalcogramma, Hypomesus olidus, Eleginus gracilis, Myoxocephalus brandti,
Tribolodon hakonensis, and Plaficntys stellatus (WGWS 1996, Ueta et al. 1996a). Humanactivities and constructions often affected prey availability (Ueta et al. 1996a, b, WGWS
1996). Open water was related to eagle distribution on large rivers in Hokkaido, but suitable
habitat and feeding places are also important (Shiraki 1996). Wintering eagles in Kamchatka
were found on large rivers with areas of open water and along the coast where open water
occurred (Lobkov & Neufeldt 1986, Nakagawa et al. 1987). The largest concentration of
wintering sea eagles was near Rausu and on Furen Lake (Nakagawa et al. 1987, WGWS
1996), and the largest counts were in February (WGWS 1996). Our results agree with thesestudies.
By late March most eagles have left the wintering grounds in Hokkaido (Nakagawa et al.
1987). The path of northward migration by juveniles Steller’s Sea Eagles followed by us
mimics part of the migration route followed by adult White-tailed Sea Eagles (Ueta et al.

891998).
The fact that juvenile eagles did not return to their natal areas is not surprising. Other
raptor species that mature only after a number of years do not show fidelity to their natal areasprior to maturation (e.g. Golden eagle Aquila chrysaetos (Haller 1996)).

ACKNOWLEDGEMENTS
The authors would like to acknowledge the help of L. Schueck, M. Bramer and S. Caquelin in
managing the ARGOS data. The research was funded by NEC Corporation, Chugach National Forest,
and the US Department of Defense. Five PTTs were donated by NTT and TOYOCOM corporations.

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