Migration timing of Pallas's Grasshopper-warbler Locustella certhiola and Lanceolated Warbler L. lanceolata at a stopover site in the Russian Far East

Abstract

The aim of our study was to describe the migration timing of two Siberian Locustella species at a breeding site in the Russian Far East. Our results show, that juvenile Lanceolated Warbler Locustella lanceolata leave the study site earlier than adults, while juvenile Pallas's Grasshopper Warbler L. certhiola start their migration later than adults, which might be caused by juveniles and adults moulting at different times. Both species undertake a fast migration without long-term stopovers at the study site.

Full text

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Ornithol Sci 18: 177 – 181 (2019)
SHORT COMMUNICATION
Migration timing of Pallas’s Grasshopper-warbler Locustella
certhiola and Lanceolated Warbler L. lanceolata at a stopover
site in the Russian Far East
László BOZÓ1,#, Wieland HEIM2, Daronja TRENSE3, Pia FETTING4, Hans-Jürgen EILTS5,
Jonas WOBKER6 and Tibor CSÖRGŐ7
1 Department of Systematic Zoology and Ecology, Eötvös Loránd University, 1117 Budapest, Pázmány Péter
stny 1/C, Hungary
2 Institute of Landscape Ecology, University of Münster, Heisenbergstraße 2, 48149 Münster, Germany
3 Institute for Integrated Natural Sciences, Department of Biology, University of Koblenz-Landau,
Universitätsstraße 1, 56070 Koblenz, Germany
4 Zoological Institute and Museum Vogelwarte Hiddensee, Soldmannstraße 23, 17489 Greifswald, Germany
5 Heimat 91C, 14165 Berlin, Germany
6 Institute for Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, Ammerländer
Heerstraße 114-118, 26129 Oldenburg, Germany
7 Department of Anatomy, Cell- and Developmental Biology, Eötvös Loránd University, 1117 Budapest, Pázmány
Péter sétány 1/C, Hungary
Abstract The aim of our study was to describe the migration timing of two Siberian
Locustella species at a breeding site in the Russian Far East. Our results show, that
juvenile Lanceolated Warbler Locustella lanceolata leave the study site earlier than
adults, while juvenile Pallas’s Grasshopper Warbler L. certhiola start their migration
later than adults, which might be caused by juveniles and adults moulting at dierent
times. Both species undertake a fast migration without long-term stopovers at the
study site.
Key words East Asian migratory yway, Locustella, Muraviovka Park
ORNITHOLOGICAL
SCIENCE
© The Ornithological Society
of Japan 2019
(Received 7 August 2018; Accepted 30 Octorber 2018)
# Corresponding author, E-mail: bozolaszlo91@gmail.com
Species in the genus Locustella live in and move
through dense vegetation both during the breeding
period and on migration (Snow et al. 1997; Nisbet
1967). At their breeding sites, they are easily identi-
ed by their specic songs (Bozó 2015), although
it is dicult to see them due to their behaviour and
morphological characteristics, but during the rest of
the year they are very dicult to nd and to identify
in the eld. Some species, such as Pallas’s Grass-
hopper Warbler L. certhiola (Pallas, 1811) and Lan-
ceolated Warbler L. lanceolata (Temminck, 1840)
occur in Europe as vagrants (Dymond et al. 1989;
Snow et al. 1997; Bozó et al. 2016), and breed across
extremely large ranges (BirdLife International 2018).
We have very limited information about their migra-
tion, wintering and breeding grounds (Nisbet 1967;
Williams 2000; Harrop 2007; Round & Baral 2013;
Round et al. 2014).
Pallas’s Grasshopper Warbler is a polytypic species
with ve subspecies (Kennerley & Pearson 2010). It
breeds from east Kazakhstan, in northeast Kyrgyzstan
and along the River Irtysh to north and northeast
China, southeast Siberia and the area around the Sea
of Okhotsk and winters from India to Southeast Asia.
Migrants return to their breeding grounds by mid-
June (Pearson 2018a) and the rst individuals reach
their Malaysian wintering grounds in mid-September.
Individual birds show both within- and between-year
wintering site delity (Nisbet 1967).
Lanceolated Warbler is a polytypic species with
two subspecies. Its breeding range includes south-
east Finland, Russia (Karelia, and from Perm and
western Urals east to lower River Kolyma, southern
Kamchatka and the Sea of Okhotsk, and south to
Altai, Amurland and Ussuriland), northern Mongolia,
northeast China and Sakhalin, the Kuril Islands and
northern Japan, and winters from northeast India

178
L. BOZÓ et al.
to the Southeast Asian islands. They return to their
breeding grounds during early June (Pearson 2018b).
At Beidaihe (northeast China) it can be observed
from August to mid-October with a peak at the end
of September (Williams 2000; Harrop 2007) and it
arrives to Hong Kong in the northeastern part of their
wintering range during October (Harrop 2007).
Here we describe the migration timing of Pallas’s
Grasshopper Warbler and Lanceolated Warbler at
Muraviovka Park in the Russian Far East. Both species
are common breeders at this study site (Heim 2014).
Following Kennerley and Pearson (2010), Pallas’s
Grasshopper Warblers breeding at Muraviovka Park
belong most likely to nominate L. c. certhiola or L.
c. minor, while L. c. rubescens could occur there on
migration.
MATERIALS AND METHODS
The study was carried out within the Amur Bird
Project (Heim & Smirenski 2013, 2017) during
spring (April to mid-June in 2013, 2015, 2016, 2017)
and autumn (July to October in 2011, 2012, 2013,
2014, 2017) migration at Muraviovka Park along the
middle reaches of the Amur River in the Russian Far
East. To dene the local population, we also consid-
ered the recapture data of birds trapped between mid-
June and mid-July. The study site is located 60 km
SE of the city of Blagoveshchensk (49°55′08,27″N,
127°40′19,93″E) (Heim et al. 2012). In total, up to
34 Japanese-type mist-nets (Ecotone, Poland) with a
total length of up to 250 m were set up in a variety of
habitats. Mist-nets were checked hourly from sunrise
to sunset.
The data analysis was carried out based on rst
captures and recaptures of 841 individuals of two
species: Pallas’s Grasshopper Warbler (rst captures:
60 in spring, 476 in autumn; recaptures: 17 in spring,
20 in summer and 111 in autumn), Lanceolated War-
bler (rst captures: 17 in spring, 118 in autumn;
recaptures: three in spring, three in summer and
16 in autumn). Species identication was based on
Svensson (1992) and Brazil (2009).
We only processed the data of the rst captures
to determine the migration timing. We used recap-
tures to determine how many days the birds spent
in the area. Moreover, it was observed how their
bodyweight changed during this period and we also
considered fat score values following Eck et al.
(2011). A fat score of 0 means that the bird did not
have any visible fat, while a fat score of 8 means
that ight muscles as well as the ventral side of the
bird are completely covered by fat. Body weight was
measured to the nearest 0.1 g. Birds trapped at least
once during the breeding period were considered to
be local. We used a t-test to describe the migration
timing of juveniles and adults and changes in body
mass during the stopover, all the variables followed
a normal distribution.
The authors conrm that all experiments were car-
ried out under the current law for scientic bird ring-
ing in Russia, and all necessary permissions were
obtained by the Moscow Bird Ringing Centre.
RESULTS
Pallas’s Grasshopper Warbler
Eighty-one percent of the migratory birds were
juveniles and 19% were adults, with juveniles migrat-
ing on average ve days later than adults (t-test,
t=6.8612, P<0.01) (see Table 1 for migration phe-
nology).
In spring, local breeding birds arrive in late May
and early June. The earliest record of a local bird
was on 31st May 2015. In autumn, on average 5.3
days (SD= 6.9) elapsed between the rst and the last
capture (N= 82). According to the recaptures, adults
Table 1. Migration timing of Pallas’s Grasshopper Warbler and Lanceolated Warbler (SD = standard
deviation, Min= earliest ringed bird, Max=latest ringed bird, N=number of ringed individuals).
Species Season Age Mean Median SD Min Max N
Pallas’s Grasshopper Warbler Spring Adult 5 Jun 5 Jun 4.4 28 May 15 Jun 39
Autumn Adult 14 Aug 14 Aug 13 25 Jul 15 Sep 89
Autumn Juvenile 19 Aug 16 Aug 13 25 Jul 21 Sep 354
Lanceolated Warbler Spring Adult 27 May 26 May 4.2 21 May 3 Jun 17
Autumn Adult 8 Sep 8 Sep 4.8 30 Aug 16 Sep 8
Autumn Juvenile 6 Sep 6 Sep 15 27 Jul 10 Oct 94

179
Migration of two Siberian Locustella species
of the local population seem to leave the area in the
second half of August and early September. There
was no signicant change in body mass during the
stopover (t-test, t =1.8862, P > 0.05) (see Table 2,
showing fat scores).
Lanceolated Warbler
Most (92.2%) of the birds were juveniles, while
7.8% were adults. Juveniles migrated on average two
days earlier than adults (t-test, t =6.8948, P< 0.01)
(see Table 1 showing migration phenology). One
adult bird caught on 9 September 2011 had a visible
brood patch.
There were 20 recaptures of 18 dierent individu-
als. One bird was re-trapped in the years after it was
banded. In autumn, on average 6.7 days (SD=5.5)
elapsed between the rst and the last capture (N = 14),
while in spring only one bird was re-trapped three
days after ringing. There was no signicant change
in body mass during the stopover (t-test, t =-1.1218,
P>0.05) (see Table 2).
DISCUSSION
Our knowledge of the migration and wintering of
Siberian Locustella species is very limited related,
therefore, we compared our results with the known
migration strategies of the European Locustella spe-
cies. These species dier in their migration strategies
(such as direction, speed, and site delity) and moult
(Mátrai et al. 2006; Neto & Gosler 2006; Křen 2008;
Neto et al. 2008; Spina & Volponi 2008; Bairlein
et al. 2014) so we might expect a similarly varied
pattern for Siberian species. However, the European
species have dierent wintering sites and several geo-
physical barriers exist across their migratory yways
including the European Alps and the Mediterranean
Sea, whereas the wintering areas of the Siberian spe-
cies are similar and there are no such major barriers
across the East Asian migratory yway (del Hoyo et
al. 2006).
The migration strategies seem similar between
the two Siberian species during spring and autumn
migration. Their migrations can be described as a
single wave, which may indicate that the dierent
populations (and in the case of Pallas’s Grasshop-
per Warbler, potentially dierent subspecies) migrate
through the same area at the same time. In a British
population of the Common Grasshopper Warbler
Locustella naevia the number of broods raised inu-
ences migration phenology (birds from different
broods migrate at dierent times; Bayly & Rumsey
2007), but our study species produce only one brood
per year.
The number of juveniles captured was remark-
ably high compared with adults and there are slight
dierences in the timing of migration of juveniles
and adults. Juvenile Lanceolated Warblers leave their
natal area earlier than the adults, which might be
explained by the fact that adults make a complete
moult on their breeding grounds (Svensson 1992),
and because of its energy-demand, this process takes
time, thus the adults are not able to start their migra-
tion earlier. Juveniles undergo only a partial moult
hence they leave rst (Miholcsa et al. 2009). This
also occurs in Savi’s Warblers Locustella luscinioi-
des (Neto et al. 2008) and Common Grasshopper
Warblers (Bayly & Rumsey 2007). However, juve-
nile Pallas’s Grasshopper Warblers start their migra-
tion later than adults, which is in agreement with a
recent study (Eilts & Heim, in preparation) that found
that only one third of the adults moulted their wing
feathers, while two thirds of the adults migrated with
unmoulted and slightly worn primaries. Additionally,
these adults began their migration while still moult-
ing. This strategy allows the adults to migrate earlier
Table 2. Fat scores and body weight of Pallas’s Grasshopper Warbler and Lanceolated Warbler (SD=standard deviation,
Min=minimum measured value, Max=maximum measured value, N= number of measured birds).
Species Age Median SD Min Max N
Fat Weight Fat Weight Fat Weight Fat Weight Fat Weight
Pallas’s Grasshopper Spring Adult 2.0 14.9 1.3 1.3 0 12.5 4 18.5 39 38
Warbler Autumn Adult 2.0 14.0 1.1 0.9 0 12.1 5 16.6 88 74
Autumn Juvenile 2.0 13.8 1.1 1.3 0 9.6 524.0 359 357
Lanceolated Warbler Spring Adult 2.0 10.7 1.3 0.9 0 9.5 5 13 16 14
Autumn Adult 1.0 12.1 1.1 1.4 0 9.1 3 13.5 8 8
Autumn Juvenile 2.0 11.1 1.3 0.9 0 9.7 5 14.5 88 84

180
L. BOZÓ et al.
after breeding than juveniles. This pattern also occurs
in the Common Grasshopper Warbler in Europe
(Rumsey 2002).
Juveniles and adults of both species have relatively
low fat scores during the spring and autumn migra-
tion and spend only a short time in the study area.
This is similar to Savi’s and Common Grasshopper
Warblers in Europe (Mátrai et al. 2006; Bayly &
Rumsey 2007; Neto et al. 2008; Bayly et al. 2011).
The East Asian migratory yway does not cross any
signicant mountain ranges or deserts, as long as
birds avoid Central Asia, and therefore it might not
be necessary for passerine migrants to accumulate
large fat deposits. Most likely, the migration strate-
gies of these species are similar to that of Savi’s
Warbler, namely fast migration without long-term
stopovers (Neto et al. 2008).
ACKNOWLEDGMENTS
The authors want to thank Sergei M. Smirenski
and the sta of Muraviovka Park as well as the
Amur Bird Project eld teams for facilitating these
studies in Far East Russia. We kindly acknowledge
the provision of rings by the Moscow Bird Ring-
ing Centre. The bird ringing program was supported
by the German Ornithologists’ Society (DO-G e.V.),
Förderkreis Allgemeine Naturkunde (Biologie) e.V.,
NABU RVE e.V. and ProRing e.V. LB’s work was
supported by the Campus Hungary Studentship and
the Hungarian National Young Talent Studentship.
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