Technical ReportPDF Available

East-West Migration of Endangered Steppe Eagle and other raptors in Thoolakharka watch site, Nepal: Migration count summary -autumn 2019

Authors:
East-West Migration of Endangered Steppe Eagle and other raptors in
Thoolakharka watch site, Nepal: Migration count summary - autumn 2019
Report Compiled by:
Sandesh Gurung, Sabin K.C., Sanjeev Baniya and Tulsi Ram Subedi
1
© Himalayan Nature 2019
Citation: Gurung, S., Kc, S. Baniya, S. and Subedi, T.R. (2019). East-West Migration of
Endangered Steppe Eagle and other raptors in Thoolakharka watch site, Nepal: Migration count
summary - autumn 2019 Technical Report 1/2019, Himalayan Nature and Nepalese Ornithological
Union, Kathmandu.
2
Birds of prey migration have been assessed from different bottleneck migrating sites of the word
(Lott 2002). Raptors breeding in the northern hemisphere of the world, leave their breeding ground
and move towards the southern warmer places to spend winter period. Annual movements of
raptors occur between Eurasia and Africa, North America and South America, Northeast Asia and
Southeast Asia and Australia (Shirihai 1987, 1988; Shirihai and Christie 1992; Meyburg et al.
2003). Migration of raptors in Asia are studied from different watch sites; Thailand, Malaysia
(DeCandido et al. 2004; Lim and Cheung 2008), Japan (Agostini and Mellone 2007) and in Nepal
(DeCandido et al. 2001; Gurung et al. 2004; Subedi et al. 2017). Long term monitoring of the
migrating raptors from the bottleneck area of their migration flyway has been used to estimate the
population status (Bednarz et al. 1990a, 1990b; Titus and Fuller 1990; Kjellén and Roos 2000;
Tholin 2011).
Here in this report we present overview of the raptor migration count conducted in central
west Nepal from the southern boundary of Annapurna Conservation Area (ACA) at Thoolakharka
watch site. In 2019, raptor migration count started from 15th October and continued until 15th of
December. Team of Himalayan Nature; Dr. Tulsi Ram Subedi, Sandesh Gurung, Sabin K.C. and
Sanjeev Baniya made observation for the migration count of raptors from Thoolakharka watch site
at Annapurna rural municipality of Kaski district, Nepal. Thoolakharka is situated at 2050 m a.s.l.
with a majestic view of Annapurna Himalaya Range on the north, Paudurkot to the south, northeast
with a Mardi River valley, east to the Hemja valley and west to the Modi River valley.
Thoolakharka provides 360 view hence we believe that the raptors doesn’t get miss when they fly
using this route. Migratory raptors along with age-class of Steppe Eagle (Photo 1, 2, 3 and 4) was
counted hourly basis starting from 08:00 hr to 17:00 hr. Soaring migrants require thermal energy
to fly (Kerlinger 1989) hence 08:00 hr was selected as starting time for migration count where the
solar intensity starts to increase slowly, 17:00 hr was selected as an end time due of the sunsets
where the thermal energy is supposed to be very low or almost absent. Additionally in our previous
studies (migration count), we did not see raptor’s activity before and after this time. Counting was
not conducted during the rainy days as no raptors found to fly during rain at our watch site. We
spent 62 days (577 hrs.) in the watch site to count the migrating raptors.
In 2019 migration count, 7 780 individuals of raptors belonging to 26 species were counted
at the watch site (Table 1). The highest single day count was on 19th November with total of 410
individuals raptors. The key species to be monitored were Steppe Eagle and the Himalayan
Vulture, the highest numbers of individuals we get every year. As such during 2019 autumn
migration we counted highest number of Steppe Eagles (n = 5 127) which was followed by
Himalayan Vulture (n = 1 677). The single day highest count of Steppe Eagle was 353 (19th
November) and the highest single hour count was on 22nd November at 12:00 - 13:00 hrs. with 114
individuals. On the other hand the highest single day count of Himalayan Vulture was found to be
on 11th of December with 105 individuals. The migration of Himalayan Vulture was recorded to
be lately compared to the Steppe Eagle.
3
Beside these two species, other migratory raptors included six species of eagle, three
species of buteo, three species of accipiter , four species of falcon, four species of vulture as well
as Black Kite (Milvus migrans ssp. govinda), Black-eared Kite (Milvus migrans sp. lineatus),
Oriental Honey Buzzard (Pernis ptilorhyncus sp. Orientalis- to name just a few.
Table 1: Raptor species observed and their number counted in 2019 autumn migration count at
Thoolakharka watch site central west Nepal.
SN
Species
Number
SN
Species
Number
1
Oriental Honey Buzzard
480
18
Black Kite
94
2
Himalayan Buzzard
50
19
Black-Eared Kite
15
3
Long-legged Buzzard
3
20
Hen Harrier
3
4
Upland Buzzard
1
21
Unidentified Harrier
0
5
Unidentified Buteo
2
22
Peregrine Falcon
2
6
Eurasian Sparrowhawk
71
23
Eurasian Hobby
32
7
Northern Goshawk
3
24
Amur Falcon
2
8
Shikra
1
25
Common Kestrel
57
9
Unidentified Accipiter
10
26
Unidentified Falcon
4
10
Steppe Eagle
5,127
27
White-rumped Vulture
38
11
Booted Eagle
7
28
Egyptian Vulture
4
12
Short-toed Eagle
1
29
Himalayan Vulture
1,677
13
Indian Spotted Eagle
1
30
Cinereous Vulture
48
14
Greater Spotted Eagle
4
31
Griffon Vulture
11
15
Bonelli's Eagle
1
32
Unidentified Vulture
16
16
Golden Eagle
1
33
Unidentified Raptor
11
17
Unidentified Eagle
3
Total of all species 7,780
Photo 1: Sub-adult Steppe Eagle passing from the Thoolakharka raptor migration watch site.
4
Most of the migration of Steppe Eagles was on latter half of the October to second week
of December. Steppe Eagle is the most notable migrants among all the raptors and the highest
individuals we get, compared to other species. In this watch site most of the raptors passes very
close to the observer, which made possible to categorize approximately 60% of Steppe Eagle to
different age classes, such as juvenile (hatched-year, Photo 3), sub-adult (2nd-4th year, Photo 1, 2,4)
and adult (≥5th year). Age class composition of migrating Steppe Eagle from Thoolakharka
showed that sub-adults occupied the highest percentage compared to juveniles and adults. Out of
total individuals, the juvenile contributed 19.31%, sub-adults 32.71% and adults 8.82%, while rest
39.17% couldn’t be identified (Fig. 1). The percentage of age class composition is almost similar
to the results of Subedi et al. (2013) while contradict with the results of Subedi and DeCandido
(2012) where the juvenile percentage was recorded higher compared to other ages.
Figure 1: Age class distribution of Steppe Eagle counted at Thoolakharka raptor migration watch
site, autumn 2019.
The count data revealed that the peak of migration started from third week of November
and lasted until last week of November. In 21st, 24th, 25th and 29th of November the weather was
worst and the visibility was poor (<1 km) hence we couldn’t locate the migrating eagles. Thus the
graph in between the peak period tended to show the sudden rise and fall in the numbers (wave
pattern, see Fig. 2).
0
500
1000
1500
2000
2500
Juvenile Sub-adult Adult Unidentified
Number of Individuals
Steppe Eagle's Age
5
Figure 2: Migration timing of Steppe Eagle (total number counted and age class categorization for
3119 eagles of known age), X axis shows migration dates and Y axis the number.
Besides these, the arrival timing of Steppe Eagle in a day was mostly high at 09:00 hr -
12:00 hr, after that the migration rate slowly decreased (Fig. 3). One of the most probable reasons
could be the availability of thermal energy at late morning compared to mid-morning and the
eagles that stayed overnight at the places east of Thoolakharka. The less count in the noon time
could be the availability of strong thermal energy close to the slopes of Himalaya range to far north
of watch site that could make us impossible to detect them.
When dense cloud fill the high mountain passes, migrants particularly Steppe Eagles shift
their flight south and into the foothills and lower valleys. For hawk watchers, the best weather
conditions for migration watching at Thoolakharka occur when clouds obscure the famous
Annapurna Range, to our north. At such time, eagles and other raptors often pass directly over the
watch site. The migrants passing from this watch site often prefer to use the thermal present at the
bare watch hill and the agriculture field closer to the observation point. This provides the hawk
watcher along with the other photographers to take beautiful closer photos of raptors which is very
difficult to obtain in other parts of the world’s raptor migration watch sites. One can get photos of
bird from a various angle sometimes even the birds passes below the eye level to the south of
watch site that even helps to produce upper body covert which is quite rare to achieve too (photo
4). Raptors are not afraid of people in Nepal because no one shoots them, nor pays them much
attention. People and raptors share the same agricultural fields that dominate the landscape of this
country, particularly the foothills of the Himalayas.
0
50
100
150
200
250
300
350
400
15-Oct 22-Oct 29-Oct 5-Nov 12-Nov 19-Nov 26-Nov 3-Dec 10-Dec
Total
Juvenile
Sub-adult
Adult
6
Figure 3: Arrival timing of Steppe Eagle on hourly basis.
The arrival of Steppe Eagle in the Thoolakharka watch site was recorded from the second
week of October very similar to the finding of Subedi and DeCandido (2012, 2013). We
incorporated the Steppe Eagle data of 2012 - 2019 to compare their population trend, counted at
the Thoolakharka raptor migration watch site. Before this we truncated 10% of the data of each
year to remove the error and total counting days for all the year were made same (15th Oct- 7th
December). The trend line of migrating Steppe Eagle revealed that the observed number of Steppe
Eagle in declining fashion (Fig. 4). If the first year migration count of Steppe Eagle (count year
2012) is considered as baseline population, our results suggest minimum of 22% declines on the
population of this species over last eight years.
Figure 4: Population trend of migrating Steppe Eagle counted at Thoolakharka watch-site during autumn
migration in 2012- 2019.
0
100
200
300
400
500
600
700
800
900
1000
Number of individuals
Time of day
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Steppe Eagle number
Year
7
Photo 2: Sub-adult Steppe Eagle passing by from the Thoolakharka raptor watch site.
Photo 3: A juvenile Steppe Eagle passing from the Thoolakharka raptor watch site.
8
The migration phenology of Steppe Eagle showed that adult and sub-adult had a peak time
started at the third week of November till to the first week of December while juveniles number
peaked at third week of November (Fig. 5).
Figure 5: Age composition of Steppe Eagles on daily basis crossing the raptor migration watch site at
Thoolakharka, Nepal 2019 autumn.
Photo 4: Sub-adult Steppe Eagle passing very close to the watch site (Note: often you get full frame with a
300 mm lens).
0
20
40
60
80
100
120
140
15-Oct 22-Oct 29-Oct 5-Nov 12-Nov 19-Nov 26-Nov 3-Dec 10-Dec
Juvenile
Sub-adult
Adult
9
Besides Steppe Eagle, we got good diversity of eagles including both resident as well as
migratory species. Seven species of eagle (including Steppe Eagle) were recorded migrating from
this watch site. Greater Spotted and Indian Spotted Eagle often came with the Steppe Eagle flock
hence making confusion to our research team. As usual a juvenile Golden Eagle made its late
appearance, almost at the end of the migration count, which is a rare migrant to us. Bonellis Eagle
and Short-toed Eagle were also recorded making journey towards west. This watch site has often
acted as a stepping stones for few raptors. Booted Eagle (Photo 5) is one of a kind that has been
often seen spending few days in the farmlands and nearest village of Thoolakharka. Few
individuals of this species make back and forth every day hence such raptors are very important to
identify or else double count can occur. We therefore try to find some of the visible marking on
such raptors for instance, any broken wings, any molted wings or any distinguishable marking so
that one can identify them easily and avoid from double counting. As usual, we got both the dark
and pale morph of Booted Eagle in our watch site.
The resident eagles included Indian Black Eagle (Photo 6), Mountain Hawk Eagle (Photo
7) and Bonelli’s Eagle. Indian Black Eagle was often recorded flying at the canopy of the tree in
search of their food while Mountain Hawk Eagle was often observed on claiming their territory
with a display flight. On 18th October we observed total of 11 unique individuals of Indian Black
Eagle and we presume that is not local population, they might do altitudinal migration. Our
previous observation in lowland during winter also supports our prediction.
Photo 5: Pale morph Booted Eagle which is quite rare in Thoolakharka (we often get dark morph).
10
Photo 6: A beautiful Indian Black Eagle often comes very close to watch site to gain the thermal.
Photo 7: Mountain Hawk Eagle photographed at the watch site, they are local birds nesting around
Thoolakharka.
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Vultures
Out of nine species of Vulture recorded in Nepal, we recorded eight species of vulture from this
watch site. We considered five species as migrants (latitudinal as well as altitudinal), in total 1 795
individuals made their journey towards west passing from the Thoolakharka raptor migration
watch site. Among them Himalayan Vulture contributed the highest percentage (93.5%) followed
by Cinereous Vulture (2.7%), White-rumped Vulture (2.1%), Griffon Vultures (0.6%) and
Egyptian Vulture (0.22%). In total 0.9% of vulture couldn’t be identified. Red-headed Vulture,
Slender-billed Vulture and Bearded Vulture were the local resident species frequently seen in the
watch site. In addition, flocks of resident Himalayan Vultures regularly pass overhead or at eye-
level. Migrations of vultures were recorded higher at noon time compared to other parts of the day.
The aloft of migration slowly started at the late morning, peaked it up till noon and started to
decline down after 13:00 hr. (Fig. 6).
Figure 6: Arrival timing of migrating Vultures on hourly basis, X axis showing time and Y axis
number.
Similar results were obtained in previous researches by Subedi and DeCandido (2012,
2013) and Subedi (2014). One of the main reasons for such a specific pattern is the availability of
the thermal. Vultures, Eagles and Kites are morphologically similar and thus use similar flight
technique (Spaar 1997). Photoperiod is thought to be the primary mechanism cueing migration
(Gwinner 1996). The solar radiation starts to increase as the day passed from morning towards
noon (Kerlinger 1989; Kerlinger and Moore 1989). Large-bodied soaring raptors are always
conscious about economizing their fuel cost by soaring using high thermal energy to migrate
(Winden et al. 2010). Thermal energy was found to be higher in noon compared to morning and
0
50
100
150
200
250
300
350
400
450
12
evening (Vansteelant et al. 2014). The timing of daily peak flights of Himalayan Vulture was
consistent with other studies that revealed most raptors observed during the middle part of the day
relying on thermals and updraft for soaring flight (Maransky et al. 1997; Mellone et al. 2012;
Pannucio et al. 2011; Punnico et al. 2013). Results of this study also match those observed in the
Turkey Vulture migration (Miller et al., 2011; Seeland et al. 2012). Migration of Himalayan
Vulture started to peak up slowly from the third second week of November till to second week of
December (Fig. 7).
Figure 7: Number of Himalayan Vulture counted on respective date during autumn migration
count 2019. X axis shows date and Y axis shows number.
Photo 8: Adult Bearded Vulture photographed from the watch site.
0.00
20.00
40.00
60.00
80.00
100.00
120.00
15-Oct 22-Oct 29-Oct 5-Nov 12-Nov 19-Nov 26-Nov 3-Dec 10-Dec
13
Photo 9: A Juvenile Himalayan Vulture photographed during the migration passage from the
watch site.
Photo 10: Sub-adult Griffon Vulture; a long distant passage migrants in Nepal.
14
Falcons
We recorded four species of falcon (Table 1) migrating from Thoolakharka watch site. Among
them, Common Kestrel (Photo 11) was highest in number followed by Eurasian Hobby (Photo
12), Peregrine Falcon (Photo 13) and Amur falcon. On 21st and 22nd we recorded the rare Amur
Falcon migrating from their breeding ground eastern Russia to the wintering ground of South
Africa. Since this year we did not perform count in late September and early October, hence lessen
number of falcons have been recorded as some species are reported to be early migrant. According
to Subedi and DeCandido (2012, 2013 and 2014) the peak time of falcons were recorded before the
third week of October hence we believe we have missed many falcons migrating from Thoolakharka.
Photo 11: Common Kestrel, a common falcon seen in migration in Thoolakharka.
15
Photo 12: Erusian Hobby in fligh (Note: The short narrow pointed wings with a orange vent).
Photo 13: Peregrine Falcon often appears near the watch site to hunt the bird
Black Kite, Oriental Honey Buzzard, Buteo and Harrier
Both the Black Kite and Black-eared Kite can be seen migrating from this watch site. This year
we observed higher number to Black Kite as compared to Black-eared Kite, in contrast our
previous record shows higher number of Black-eared Kite. Oriental Honey Buzzard held the third
position to pass higher number compared to all raptor species (Table 1). Most of the Oriental
Honey Buzzard we record from watch site were juvenile. We got various morphs including dark,
pale, white as well as rufous morph. This raptor is often harassed by corvids and observed chased
by the flock of Large-billed Crows.
16
This year we recorded three species of Buteo: Himalayan Buzzard (Photo 14), Long-legged
Buzzard and Upland Buzzard during autumn migration count. Three individuals Hen Harrier were
recorded migrating from Thoolakharka raptor migration watch site, which is another rare species
here.
Photo 14: A juvenile Himalayan Buzzard.
Accipiter
This year we observed three different species of Accipiter. Among them Eurasian Sparrowhawk
occupied the highest number followed by Northern Goshawk and Shikra. We used Nikon D7000
camera with a 200-500 mm zoom Nikor lens to take picture and identify it in case we felt difficult
by our binocular. Besra and Shikra were often seen making a maneuver flight against Large-billed
Crow.
17
Acknowledgements
We thank Japan Fund for Global Environment for the financial support through Japanese Society
for the Preservation of Birds (JSPB). We thank Dr. Hem Sagar Baral, a senior ornithologist of
Nepal, and Sharad Singh, Admin and Finance Director of Himalayan Nature for valuable
suggestion. We thank Department of National Park and Wildlife Conservation (CNPWC) and
Annapurna Conservation Area Project (ACAP) for granting us permit to conduct this study. We
thank our friend and officer at ACAP Rishi Baral for various support. Thank to Dr. Chaiyan
Kasorndorkbua and Thai Raptor Group for continuous encouragement and suggestion during the
count. We express thanks and sincere gratitude to Dr. Toru Yamazaki, Yasunori Nitani, Takashi Fujii
and Mountain Hawk Eagle team and JSPB members from Japan for their constructive suggestion,
untiring help, guidance and their practical suggestions that inspired us to accomplish this work
successfully. We also thank Prakasit Chancharas from Thailand, Jacky Soh and Virginia Cheang from
Singapore for their donation to the project. We also thank Raju Acharya, CEO of Friends of Nature for
his support in our raptor count. Finally we express thank to Hari KC and Australian Camp Guest House
family, Nirmal Gurung and Sunrise Restaurant family for their hospitality and support throughout the
research period.
Landscape to the north of Thoolakharka Raptor migration watch site- The Annapurna Himalaya
Range (Photo: Tulsi Subedi)
18
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... After 24 Nov. the number of eagles declined and suddenly peaked on 3 rd December with the highest count record (300 birds) in a single day (Fig 2). Since the migration timing and peak time of Steppe Eagle was found to be very similar compared to earlier years autumn count i.e. 2012-2015, 2017, 2018, and 2019 respectively (Subedi and DeCandido 2012, Subedi et al 2013, Subedi and Gurung 2018, Gurung et al 2019. One of the reasons for the highest count of the eagles in a single day towards the end of the season could be the sudden changes in the weather conditions that might have to pressurize the migrating eagles as well as wintering eagles nearby the watch site as a stepping stone to move furthermore west for a warmer area. ...
... The highest individuals were Amur Falcons followed by Eurasian Hobby, Common Kestrel, Peregrine Falcon, Lesser Kestrel and the globally endangered Saker Falcon. Surprisingly, the number of one species (Amur Falcon) in this year was higher compared to other years, however, the total numbers of all falcons are not significantly larger than previous counts (Gurung et al 2019). ...
... . Comparing present numbers with the previous monitoring records (2012 -2019), the numbers of migrating raptors have declined(Subedi and DeCandido 2012, Subedi and DeCandido 2013, Subedi 2014, Subedi and Gurung 2018, Gurung et al 2019. ...
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