Результаты весенних авиаучетов птиц в российском секторе Финского залива

Ekosistemy, 36: 114–132 (2023) https://ekosystems.cfuv.ru

УДК 591.543.43: 598.252: 598.243.8: 598.279 DOI 10.5281/zenodo.10376842

Bubluchenko J. N.1, Bubluchenko A. G.3, Verevkin M. V.3

The main results of spring aerial survey of birds at the Russian part of the Gulf of Finland

  1. Nature conservation Department of Leningradsky ZOO, Saint-Petersburg, Russian Federation julandb@mail.ru
  2. Zoological institute of Russian Academy of Sciences, Saint-Petersburg, Russian Federation abublichenko@mail.ru
  3. Saint-Petersburg Research Centre of Russian Academy of Sciences, Saint-Petersburg, Russian Federation vermiv@yandex.ru

The paper presents results of three-season spring bird aerial surveys in the Russian part of the Gulf of Finland of the Baltic Sea. The research involved surveying the water area of seven Protected Areas –“East of the Gulf of Finland”, “Berezovye Islands”, “Kurgalsky”, “Vyborgsky”, “Kotelsky”, “Lebyazhy”, “Western Kotlin”. The main goal of this research was to monitor previously known and to discover new mass stopovers of marine, waterfowl and shore birds during the spring migration, to clarify the large breeding bird colonies location in this region, as well as to assess possible changes in their current location, number and bird species composition due to the ever-increasing anthropogenic pressure on ecosystems of the Gulf of Finland. Bird counts were performed in spring 2016-2020. The total time of aerial surveys was more than 39 hours (about 4.5 hours per day count). Surveys were carried out twice a season in 2016 and 2020, four times in 2018 with an interval of 5-7 days, which was due to the necessity to obtain data on changes in the species composition of migratory birds and changes in stopover locations, as well as fixing the beginning of reproduction period., Furthermore, 18 066 photographs were taken and analyzed. In total, 81 509 birds of 53 species from 8 orders were recorded during the observation period; moreover 24 species were included into Red Data lists of different ranks. Data obtained revealed 15 main sites of migratory bird stopovers and 9 main breeding areas in the surveyed area. They made it possible to compile more complete picture of migratory bird stopovers, supplementing the already known information with data on migrants and mass breeding birds. It also should be noted that such detailed aerial bird surveys in vast water areas were conducted for the first time in this region.

Keywords: spring migration, spring stopovers, shore birds, waterfowl, breeding colonies.

INTRODUCTION

The Gulf of Finland (Finnish: Suomenlahti; Estonian: Soome laht; Swedish: Finska viken) is the easternmost part of the Baltic Sea. It extends between Finland (to the north), Russia (to the east) and Estonia (to the south). The Gulf west border is an imaginary line between the Hanko peninsula and Põõsaspea cape. The gulf has an area of 29,500 km2, the length is 420 km and the width varies from 70 km near the entrance to 130 km in the widest part. The eastern (Russian) part of the Gulf of Finland has a water area of more than 11,000 km2 and a coastline in a complex configuration of more than 500 km. The gulf is relatively shallow, with the depth decreasing from the entrance of the gulf to the continent. The average depth is 38 m, the maximal depth is 121 m; near to shore it is about one m. The gulf abounds with shoals, banks, skerries and islands. The largest islands in investigated area are Kotlin Island with Kronstadt, Beryozovye Islands, Gogland, Moshny, Malyi Tyuters, Bolshoy Tyuters, Seskar etc.

Shoals with the depth of less than 10 m occupy about a quarter of the Gulf of Finland. Among them, the vastest shoals are the Nevskaya Bay, area around Berezovye Islands, the Koporskaya Bay, the shoals around Kurgalskii peninsula, Kotlin, Seskar, Moshnyi, Malyi and Malyi Tyuters islands. These zones are well-warmed up, aerated and properly lit and have high biological productivity and huge feeding resources and able to feed millions of migratory birds (Noskov, 1997, 2002).

In total, 19 protected areas of various ranks are located on the Gulf coast and islands, including the National Park «East of the Gulf of Finland».

ISSN 2414-4738 Published by V. I. Vernadsky Crimean Federal University, Simferopol

 

The main results of spring aerial survey of birds at the Russian part of the Gulf of Finland

Birds are the largest and most diverse of vertebrates group inhabiting the mainland coast and islands of the Gulf of Finland. During the seasonal migrations, up to 230–235 species can be seen in the Gulf and adjacent area (including forest biotopes). The 2016–2020 aerial surveys were aimed at obtaining a more complete picture of the spring migration in the eastern part of the Gulf of Finland and clarifying migration stopover sites here.

MATERIAL AND METHODS

At present time aerial remote sensing surveys are becoming more popular as they can be used to monitor animals in their natural habitats without disturbing them. Previously, the details achievable by high spatial resolution aerial imagery enabled the population estimation of only a few bird species. Nowadays, high spatial resolution and high-speed digital cameras have recorded open land surfaces at high altitudes during high-speed flights. Thus, animals do not perceive the aircraft passing over them (Aerial Surveys…, 2008; Certain, Bretagnolle, 2008; Delani, 2011; Báko et al., 2014; Porter et al., 2021). High resolution modern digital cameras allow acquiring the detailed images of single birds and flocks on water and an open coastline at a distance. During this photographing, birds do not feel the close presence of observers, which makes it possible to carry out the most accurate counts with minimal disturbance. Aerial photography is one of the best methods of counting in vast, remote areas (Concepts of Aerial Photography…, 2019), including marine waters, and an important way to identify areas of migratory concentrations of birds. Slow-flying aircraft is considered the most suitable aircraft for aerial photography: with their help, large areas can be inspected and large amounts of information can be collected in a short time (Aerial Surveys…, 2008; Delani, 2011; Bublichenko J., Bublichenko A., 2015).

The aerial surveys were performed in the Russian part of the Gulf of Finland. Bird counts were performed on 23.04.2016; 8.05.2016; 14.04.2018; 18.04.2018; 13.05.2018; 15.05.2018; 26.05.2020; 2.06.2020 which made it possible to identify birds’ stopovers during the all migratory season and nest colonies of large bird species.

During the aerial surveys we performed the total counting of all flocks and single birds both flying and sitting on the shore or water. In addition, we made pictures of the main waterfowl migratory sites and breeding habitats. We plotted all routes for bird aerial surveys through sites of the most probable stopovers according to published data (Putkonen, 1936, 1940, 1942) Noskov et al., 1965; Noskov, Rezvy, 1995; Bublichenko, Kozlov, 1998, Bojarinova, Bublichenko, 2001; Vassiljeva, 2001; Buzun, 2001; Noskov, 2002; Iovchenko et al., 2006; Bublichenko, 2007a, Bublichenko, 2007b; Rymkevich et al., 2009; Noskov et al., 2016; Bublichenko, Verevkin, 2017, 2018; Bublichenko, 2018; etc.).

Surveys were carried out onboard of the aircraft Cessna 182, leased from the Aero club NP «Nevsky Aero Club» (Air Operator Certificate AP-13-10-003). The pilot was qualified as a commercial pilot and had many years of experience in providing counts of birds and marine mammals.

Weather conditions were carefully examined before takeoff and flights only started when weather conditions were equivalent or better to: sea state ≤ Beaufort 3, little cloudy with minimal wind (no more than 2–3 m/sec), absence of rain or fog etc. (Table 1).

The average flight speed on transects was 180–200 km/h. The average height of the flight (90

  1. was maintained by the pilots with the help of a radar altimeter. The speed of the aircraft at the time of observing bird flocks and the detected stopovers varied from 70 to 90 km/h. A relatively slow airspeed enhanced the accuracy and reliability of counting, as it allowed to observe investigated area, and therefore not to miss the target.

The observations were performed by two experienced researchers from two sides of the aircraft. The first observer was sitting on the port side, the second observer – on the starboard. All equipment was used according to the HELCOM standards: 1) high-wing fixed aircraft with opening window; 2) digital cameras with zoom lenses 200-300 mm in their range and image stabilizer. We used cameras with high resolution (Canon EOS 40D with lenses Canon70–200 mm and Nikon D750 with

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Table 1

 
   

Weather conditions during the observation days

     
                   
 

Tempera-

Atmosphere

Cloudiness

Wind

Wind

Visibility

Precipitation

Degree of ice

 
 

ture (°C)

pressure

(%)

(m/sec)

direction

(кm)

coverage

 
 

(mm)

 

(%)

 
               

23.04.2016

+8

754

50

1

S

10

0

5

 
                   

08.05.2016

+20

768

0

2

NW

10

0

0

 
                   

14.04.2018

+2,4

772

30

2

W

20

0

50

 
                   

18.04.2018

+5

763

40–60

3

NE

4

0

30

 
                   

13.05.2018

+12,3

768

10

1

NE

10

0

0

 
                   

15.05.2018

+20

764

0

1

SE

10

0

0

 
                   

26.05.2020

+21

772

30

1

NW

10

0

0

 
                   

02.06.2020

+17

765

0

2

NW

20

0

0

 
                   

Nikkor 70–300 mm and GPS tags for each photo; 3) binoculars; 4) GPS receivers Garmin GPS map 60CX and Nikon GP-1 GPS Unit etc.

During the aerial surveys we explored the following islands (Fig. 1): small islets of the Kurgalsky Reef (1) and the Reimosar Island (2) (“Kurgalsky” Nature Reserve), Vigrund (3), Bolshoi Tyuters (4), Malyi Tyuters (5), North and South Virgins (6) (“East of the Gulf of Finland” Wildlife Reserve), Rodsher (7), Gogland (8), Bolshoi Fiskar archipelago (9) (“East of the Gulf of Finland” Wildlife Reserve), the Berezovye Islands (10), including the Rondo (11) (“Berezovye Islands” Nature Reserve), Kotlin (12) (“Western Kotlin” Nature Reserve), Seskar (13) (“East of the Gulf of Finland” Wildlife Reserve), Malyi (14), Moshnyi (15). We also examined the southern mainland coast from the “Lebyazhy” regional Reserve through Chernaya Lachta vill. and the Koporskaya Bay (“Kotelsky” regional Nature Reserve) to the Kurgalsky Peninsula and Narva Bay (Fig. 1, 2). In addition, we grouped birds marked in the open area to the nearest islands.

Fig. 1. Location of islands and reefs where aerial bird surveys were carried out

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The main results of spring aerial survey of birds at the Russian part of the Gulf of Finland

Fig. 2. Example of the aerial survey route (26th May 2020)

During each aerial survey, we recorded coordinates and took pictures of all flocks and single birds found sitting on the water, on the shoreline, on an ice floe and flying by transit. Some individuals or flocks were not possible to identify from the air due to their subtle differences in identifying characteristics that were not visible at distance, because of lighting features or high speed. These species were grouped into broader taxonomic categories (e. g. “unidentified ducks”, “unidentified swans”, “Melanitta sp”, “terns’) according to easily identifiable characteristics (general size, shape, color: e. g. “black-backed gulls”, “silver gulls”) allowed (Stehn et al., 2008).

The total time of aerial surveys was more than 39 hours (about 4.5 hours per day count). The survey was carried out twice a season in 2016 and 2020, four times in 2018 with an interval of 5–7 days, which was due to the necessity to obtain data on changes in the species composition of migratory birds and changes in stopover locations. All flight routes were designed to visit the most important sites for migratory and breeding birds (Fig.2). The total route length was more than 6 500 km (about 900 km per each count). 18 066 photographs were taken and then analyzed in 2016–2020 by both surveyors (Table 2).

                 

Table 2

   

Number of images taken and analyzed in 2016–2020

   
                   
 

14.04.2018

18.04.2018

23.04.2016

8.05.2016

13.05.2018

15.05.2018

26.05.2020

2.06.2020

Total

                   

Starboard

367

784

1133

742

1700

1008

1903

1852

 
                   

Portside

298

689

1101

1338

1430

1804

689

1228

 
                   

Total

665

1473

2234

2080

3130

2812

2592

3080

18066

                   

All photographs were reviewed and, if necessary, processed in the following programs: Nikon View NX2, Fast Stone Image Viewer, Adobe Photoshop CC 2018. The coordinates of the marked waterfowl flocks were transferred to the map of Gulf of Finland in the Quantum GIS 2.8 program to create the map of the most important stopovers. Maps of the work area and meeting points of flocks of birds were also created in Quantum GIS, and then the main stopover plots were combined in Adobe Photoshop CC 2018. All data about bird records, bird number, diagrams and the main stopover and breeding areas coordinates were entered and created in the Excel 2018.

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Bubluchenko J. N., Bubluchenko A. G., Verevkin M. V.

Avifauna of the Gulf of Finland islands

Birds are the largest and most diverse of vertebrates group inhabiting the mainland coast and islands of the Gulf of Finland. During the seasonal migrations up to 230–235 species can be seen in the Gulf and adjacent area (including forest biotopes). In total, the avifauna of the mainland coast and islands includes more than 80 % of birds recorded in the Leningrad Region; 59 bird species of these are rare and protected in the region (Bublichenko et al., 2018); 28 bird species are included in the HELCOM Red List (Kontula, Haldin, 2013); 14 bird species are in the Red Data Book of the Russian Federation (Pavlov, 2021); 4 bird species are in IUCN International List of Threatened Species of Animals and Plants (IUCN Red List, 2020) (Bublichenko J., Bublichenko A., 2020).

A significant part of coastal bird habitats is currently represented in 10 existing ‘KBA’ (Kondratyev, 2000), part of the International Program “Important Bird Areas” (IBA), one Federal and 18 regional reserves. Speaking about the peculiarities of the bird habitats structure on the coastal and insular areas of the Gulf of Finland region, it is necessary to emphasize the natural heterogeneity of these territories, and, as a result, the presence of completely different ecological groups of birds here (Bublichenko, 2014).

Features of spring bird migration in the Russian part of the Gulf of Finland

The Gulf of Finland plays an important role as a “bottleneck” for millions of migrants. This role of the “accumulator” of migratory waterfowl, shore birds and another species is also determined by climatic and biocenotic factors (Kontiokorpi, 2000); Noskov, Rymkevich, 2014, 2016).

The vast majority of waterfowl and seabirds enters the Gulf of Finland from the Baltic regions in spring (Noskov et al., 1965, 1995 a, Noskov et al., 1995b; 2016; Noskov, 1997, 2002; Noskov, Rymkevich, 2014, 2016). Observations of the spring migration in recent decades show that two main flight paths of waterbirds crossing the Leningrad region (Noskov, 2002) continue to operate in North-West Russia. The first one is eastward to the Neva Bay and further along the south coast of Lake Ladoga to Svir Bay, the second one (the most significant for the research performed) goes from the Gulf of Riga in the Baltic Sea through the central part of the Gulf of Finland to the Vyborg Bay and further north through the Karelian Isthmus and Ladoga Lake. A lot of arctic species (loons, Whooper Swan, brent geese, sea ducks and gulls) fly along this migration path. At the same time, the Gulf is not an area with huge stopover sites of arctic migrants, with a few exceptions, such as Aythya marila, loons and swans (Buzun, 2001; Noskov, 2002; Bublichenko, Kouzov, 2015; Rintala et al., 2016; Bublichenko, Verevkin, 2018). Mass swan stopovers (Cygnus olor, C. cygnus and C. bewickii) were found in the northern part of the Gulf of Finland in the shallow waters around the Beryozovye islands (Bublichenko, 2007a, Bublichenko, 2007b, 2015), as well as near the Kurgalsky Reef and the Pihlisar Cape of Kurgalsky Peninsula (Bublichenko, Kozlov, 1998; Bublichenko, 2000; Bublichenko J., Bublichenko A., 2020, etc.). In recent years, large concentrations of geese, ducks and gulls resting and feeding, were also observed at the investigated area (Kontiokorpi, Parviainen, 1995; Rychkova, 2009; Rymkevich et al., 2009; Kouzov, Kravchuk, 2011a; Sagitov, 2012; Iovchenko et al., 2017; Pchelintsev, Chaadaeva, 2020, etc.). Large transit flocks and stopovers of Branta leucopsis were registered on the islands and peninsulas of the Gulf of Finland during the spring migration (Noskov et al., 1993; Bublichenko, Kozlov, 1998; Leito, 1999; Bojarinova, Bublichenko, 2001; Vassiljeva, 2001; Kouzov, Kravchuk, 2011b; Noskov et al., 2016).

It should be clarified that the first aerial surveys of water birds in this region were carried out from a helicopter in May 2002 in the Vyborg Bay and Berezovye Islands area (Iovchenko et al., 2006). Later, in the Russian part of the Gulf of Finland, first spring aerial surveys were conducted in 2016, 2018 (Bublichenko, Verevkin, 2017, 2018) and 2020. They made it possible to clarify the species composition and stopovers location, to assess the intensity of the migration flow of geese, brants, many duck species and other birds during the spring time, to assess the possibility/degree of impact of the gas pipeline construction on migratory stopovers and key bird breeding areas. Aerial surveys in 2016–2020 made it possible to compile a more complete picture of migratory bird stopovers, supplementing the already known information with data on migrants.

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The main results of spring aerial survey of birds at the Russian part of the Gulf of Finland

RESULTS

In total, 81 509 birds of 53 species from eight orders were recorded during the observation period (Table 3). Of all recorded species, 10 bird species are included in IUCN Red list (2020); 22 – in the Red Data Book of animals of the Leningrad Region (2018), 8 – in the Red Data Book of Russian Federation (2021), and 11 – in the HELCOM Red List of birds (2013) (Table 4).

             

Table 3

   

Birds registered in different years

   
               

Orders

2016

 

2018

2020

 

Total

Number of species

               

Gaviiformes

 

2

2

 

4

1

Podicipedidae

16

 

17

 

33

2

Pelecaniformes

2758

 

10447

12369

 

25574

1

               

Ciconiiformes

7

 

3

50

 

60

2

               

Anseriformes

11170

 

11818

6549

 

29537

28

               

Falconiformes

1

 

4

6

 

11

1

               

Gruiformes

 

2

2

 

4

2

Charadriiformes

6614

 

11089

8583

 

26286

16

               
 

20566

 

33382

27561

 

81509

53

               

Anatidae (Anseriformes) dominated during the observation period (Fig. 3), their total number was 29 537 individuals, i. e. 36 % of the total number of registered birds. The total number of recorded Anatidae species was 28; the most numerous were Bucephala clangula (788 ind. – in 2016, 942 – in 2018, 2631 – in 2020), Clangula hyemalis (more than 1400 annually: 1106 in 2016, 1402 – in 2018, 1405 – in 2020), Melanitta gr. (1030 in 2016, 4190 – in 2018, 166 – in 2020). A large difference in the number of migratory birds such as Anser anser (1156 ind. in 2016, 763 – in 2018, 374 – in 2020), Branta leucopsis (153, 631, 78, respectively), Anser fabalis (270, 104, 0, respectively), Mergus merganser (177, 364, 301, respectively) and Melanitta gr. can be explained by different timing of the counts.

As a rule, Cygnus olor, Cygnus cygnus, Mergus merganser, Somateria mollissima, Anser anser and Aythya fuligula, were flying in small flocks (up to 15–20- individuals, as a rule). Most other birds were observed in flocks of 15–30 individuals at least (Branta leucopsis, Anas penelope, Anas platyrhynchos, Mergus serrator). Bucephala clangula, Сlangula hyemalis – from 60 to 100 and more birds in a flock, Melaniita nigra and M. fusca (more than 100–200 birds as a rule) formed the largest flocks.

Numerous nonbreeding duck flocks concentrate in the Gulf of Finland in early summer (Noskov, Rymkevich, 2016). In 2020, the authors registered the beginning of formation of such flocks for Anas platyrhynchos (237 individuals), Aythya fuligula (102) and Anas penelope (81).

Gulls (Laridae) and Phalacrocorax carbo were the most numerous (Fig. 3). They amounted up to 57.6 % (up to 7 050 and 12 369, in 2020, respectively) of all registered birds. Low number of cormorants during the aerial counts in 2016 is explained, from our point of view, by the late ice melting in the Gulf that season. It is known that the number of this species were constantly high in recent years on breeding sites, and it has increased in many colonies significantly (Gaginskaya, Rychkova, 2011; Bublichenko, Kouzov, 2015; Bublichenko, 2016a, Bublichenko, 2016b).

The most numerous species from the gulls (up to 9519 individuals in 2018, Fig. 3) was Larus argentatus (about 5000–6000 individuals per year), it’s more than 24 % of the total bird number observed. But the significant part of the registered both European herring gulls and great cormorants were already sitting on the nests in May-beginning of June. We fixed all breeding sites and feeding places for these species. In April, 2016, due to the late ice melting, we were able to register both migrants and birds that had just arrived at the nesting sites.

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Table 4

 

The list of rare bird species registered during the observation period 2016–2020

 
                               

Scientific name

Krg

BI

MT

BT

BF

S

KBL

G

M

Ml

R

Kt

Vrg

Nature-conservation

 

status

 
                             

Gavia arctica

+

+

L3; H(CRw); RF2

 
                               

Podiceps auritus

+

L3; EU(EN)

 
                               

Branta leucopsis

+

+

+

+

+

+

LB

 
                               

Branta bernicla

+

+

+

+

+

L4; H(NTw); RF3

 
                               

Anser anser

+

+

+

+

+

+

+

+

+

+

RF2; L3

 
                               

Anser erythropus

+

L1; VU; RF2

 
                               

Cygnus cygnus

+

+

+

+

+

+

+

+

L3

 
                               

Cygnus bewickii

+

+

+

+

+

+

+

L5; EU(EN); RF5

 
                               

Tadorna tadorna

+

L4

 
                               

Anas strepera

+

+

+

+

L3

 
                               

Anas acuta

+

+

L3

 
                               

Aythya ferina

+

+

+

+

+

EU(VU)

 
                               

Aythya fuligula

+

+

+

+

+

+

+

+

+

+

+

+

+

H(NTb)

 
                               

Aythya marila

+

+

+

+

+

H(VUb)

 
                               

Clangula hyemalis

+

+

+

+

+

+

+

+

+

+

+

H (ENw); EU(VU)

 
                               

Somateria mоllissima

+

+

+

+

+

+

+

+

+

+

+

+

+

L3; EU(VU);

 

H(ENw;VUb)

 
                             

Melanitta nigra

+

+

+

+

+

+

+

H (ENw)

 
                               

Melanitta fusca

+

+

+

+

+

+

H(ENw;VUb)

 
                               

Mergus serrator

+

+

+

+

+

+

+

+

+

+

+

+

+

EU(NT); H (VUb)

 
                               

Mergus merganser

+

+

+

+

+

+

+

+

+

L4

 
                               

Haliaeetus albicilla

+

+

+

+

+

RF5; L3

 
                               

Haematopus

+

+

+

+

+

+

+

RF3; L3

 

ostralegus

 
                             

Larus fuscus

+

+

+

+

+

+

+

+

+

+

L2; EU(NT); H(VUb);

 

RF2

 
                             

Hydroprogne caspia

+

RF3; H(VUb); L(B)

 
                               

Notes. 1) IUCN Red List (2019): EN – Endangered; VU – vulnerable species; NT is a potentially vulnerable species;

  1. Red Data Book of the Russian Federation (2020). Categories of the rarity status of objects of the animal world (RF): 0 – probably disappeared, 1 – endangered, 2 – decreasing in number and/or distribution, 3 – rare, 4 – undefined in status, 5 – restored and restored; 3) Helcom Red List of Baltic Sea species in danger of becoming extinct: Нb – list for breeding species, Нw – list for wintering species; CR – in critical condition; EN – endangered; VU – vulnerable species; NT is a potentially vulnerable species; 4) Red Data Book of Nature of the Leningrad Region. Animals (2018) (L): 0 – probably extinct; 1 – a species in critical condition; 2 – a species with a diminishing range and number; 3 – rare species; 4 – species with an undefined status; 5 – species restoring numbers; B – species included in the lists requiring attention (‘bio-surveillance’); 6) Krg – Kurgalsky reserve & Narva Bay, BI – Berezoviye isl., MT – Maly Tyuters, BT – Bolshoi Tyuters, BF – Bolshoi Fiskar, V – Virgins, S – Seskar, KBL – Koporskaya Bay – Lebyazhy, G – Gogland, M – Mozshny, Ml –Maly, R – Rodsher, Kt – Kotlin, Vrg – Vigrund.

We recorded the largest colonies of Phalacrocorax carbo at six sites: on the Kurgalsky Reef islets and the Reimosar island near the Kurgalsky Peninsula, on small islands near the Seskar Island, on Virgin Islands, on the Bolshoi Fiskar archipelago and to a lesser extent on the Berezoviye Islands (Fig. 1).

The main breeding areas of Larus argentatus were located at eight sites (Fig. 1): on the Kurgalsky Reef and Reimosar islands, on small islands near the Seskar Island, on Maly Tyuters, Rodsher, South and North Virgin Islands, on the Bolshoi Fiskar and Berezoviye archipelagos. We

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Fig. 3. The number of different birds in the years of aerial counts

recorded tern colonies on the sandy spit of the Kurgalsky Reef, on Maly Tyuters, Virgins and Rodsher islands. Chroicocephalus ridibundus and Larus canus colonies were found on the Maly Tyuters Island. Moreover, Larus canus often used rocky stones as a restplaces on the Gogland Island coastal zone.

Phalacrocorax carbo, Alca torda and Uria aalge colonies were recorded on the North Virgin Island. Large Alca torda colony (143 birds in 2020) has also been recorded on Rodsher Island too. Small colonies of Larus fuscus were fixed on Moshnyi, Kokkor (near Moshnyi), Bolshoi Fiskar, Berezoviye islands. At the same time, this species was not registered on the Rondo Island (Berezoviye Islands archipelago) in 2020, however, this species had had a large colony in previous years there (Bublichenko, 2007b). Several pairs of Anser anser and Branta leucopsis were recorded on the Bolshoi Fiskar and Berezovye Islands archipelago (Zvenyevoy and Rondo islands) in 2018– 2020.

The aerial survey method also proved to be quite accurate for determining the number of Cygnus olor breeding pairs. For instance, not only the nests themselves were clearly visible, but birds with broods on the water. Nests (in 2016–2020) and broods (in 2020 only) were found on “Kurgalsky” reserve, Bolshoi Fiskar, Maly, Maly Tyuters, Seskar, Mozshy, Rondo islands.

The research team encountered with Haliaeetus albicilla annually. The most preferable foraging sites in spring are Kurgalsky Reef, Seskar, Halikarty, Bolshoi Fiskar (Fig. 4), Maly Tyuters, Berezoviye islands. Data obtained confirm the results of our observations in 2019–2020 and the information from other authors (Sagitov, 2012; Kouzov et al., 2014; Pchelintsev, 2016) which were carried out during the route counts and counts from vessels. It is known, that this species has nests on the Kurgalsky Penninsula, Kokkor and several other islands, probably (Kouzov et al., 2014; Pchelintsev, 2016). So, in 2020 we found one nest of Haliaeetus albicilla on the Gogland Island and one pair on the Maly Tyuters Island.

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Fig. 4. White-tailed eagles on the Bolshoi Fiskar Island on 02.06.2020

In 2020, we registered an increase in the Casmerodius albus number (44 individuals per two-day counting), whose numbers in the Gulf of Finland significantly increased in recent years (Kouzov et al., 2019). So, from 1 (Golovan, 2011) to 7 Casmerodius albus (Dombrovsky, 2015; Golovan et al., 2015) were recorded in 2011–2015 in the observation area during the spring migrations in 2011– 2015.

During the aerial surveys, other bird species were also recorded: Podiceps cristatus, Ardea cinerea; Grus grus, Fulica atra, Larus marinus, Haematopus ostralegus etc.

Due to the fact that the spring migration of sea birds, waterfowl and shore birds is very extended in this region (from the end of March to the end of May-beginning of June) (Bublichenko, Kozlov, 1998; Bojarinova, Bublichenko, 2001; Buzun, 2001; Rychkova, 2009; Rymkevich, 2009; Pyatraitis, 2014; Noskov et al., 2016) we did not try to reveal the timing of mass migrations during the observation period, but to determine the most important stopovers in this part of the Gulf of Finland, detect whether migratory birds still stop here and whether they fly by transit here. Besides, we wanted to count how many bird colonies exist on investigated area nowadays.

We registered the largest bird stopovers on shallow waters and coastal areas: Koporskaya Bay, Narva Bay, Kurgalsky Peninsula with the Kurgalsky Reef islets, Seskar, Moshnyi, Maly, Maly Tyuters, islands, the Berezovye Islands and the Bolshoi Fiskar archipelagos, the area of the Lebyazhye-Chernaya Lakhta mainland coast (Fig. 5, 6). Small flocks were also registered near Bolshoy Tyuters, Rodsher, Gogland, Kotlin, South and North Virgins islands. It is important that Maly Tyuters, Rodsher, South and North Virgins and Kurgalsky Peninsula are situated near the gas pipe line. Besides, a lot of resting and feeding sites were located in numerous shallow waters around those and other investigated islands of the Gulf of Finland and on mainland coastal areas; somewhat less often – on single large stones protruding from the water, or on banks. Mass migrations of sea ducks were recorded in Narva Bay, near the Bolshoi Fiskar archipelago and near Seskar and Moshnyi islands shallow waters.

We also paid attention to whether transit bird flocks flying in the gas pipeline “NordStream 2” construction area in the Narva bay and open water area. About 10–15 flocks we registered each day of aerial counts during all years of observations. The most numerous were Anser anser, A. albifrons, Branta leucopsis, Clangula hyemalis, Phalacrocorax carbo, Melanitta sp., Larus argentatus.

More detailed results of our observations about migratory and breeding birds from the main sites in the Russian part of the Gulf of Finland are presented below.

The Kurgalsky peninsula together with the adjacent Kurgalsky Reef and Reymosar islands is a unique habitat for many bird species, including waterfowl and shore birds. The Kurgalsky

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Fig. 5. Ratio of bird numbers in the investigated area during the observation

period 2016–2020

Fig. 6. The most important stopovers and breeding colonies in the Russian part of the Gulf of Finland allocated in accordance with the results of aerial surveys

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peninsula is located on the border with Estonia. The entire surveyed coastal area and small islands surrounding the peninsula are the part of the “Kurgalsky” Nature Reserve, one of Important Bird Areas (IBA) and Ramsar sites in Russia. Its southern coastline is crossed over by the gas pipeline. But the most important reserve areas, most suitable for breeding the majority of rare water birds, are located in the northern and north-western parts of the reserve. The nearest site to the gas pipeline, valuable for breeding birds and migratory stopovers, is the Reimosar Island and adjacent area. However, this plot is located at a considerable distance from the gas pipeline route (more than 10 km).

The entire central part of the peninsula is covered with different types of forests. A significant part of the coast and adjacent islands are covered with coastal meadows, has many sandy beaches and rocky shoals suitable for both migratory stopovers and breeding birds.

The waterfowl and shore birds fauna is well studied here; monitoring of the avifauna has been continuing at the present time here (Bublichenko, 2016b, Bublichenko, 2016 ); Kouzov, Kravchuk, 2011, 2020; Pchelintsev, Chaadaeva, 2020, etc.). Over the previous research years, it was noted that

  1. significant part of migrants (e.g. Melanitta nigra, M. fusca, Сlangula hyemalis, geese, arctic waders) fly by transit through the peninsula, making their main stopovers near the Moshnyi, Seskar and Maly islands (Noskov, 1997, 2002; Noskov, Rymkevich, 2014, 2016; Noskov et al., 2016). However, shallow waters around the Kurgalsky Reef are also a habitat for a number of not only breeding but also for migratory species too. Besides, Narva Bay and Ust-Luga Bay (despite the Ust-Luga port operation) aquatic area are very important for migrants.

The total bird number registered near the Kurgalsky Peninsula was about 9 000 individuals for two days of counting per year in 2018–2020 (Fig. 5). In total, 30 species from 5 orders were recorded off the coast of the Kurgalsky Peninsula. Three bird groups dominated here: Pelecaniformes (Phalacrocorax carbo, up to 64 % of the total number of registered birds in different years), Anseriformes (up to 20 species, 16–25 %) and Charadriiformes (up to 8 species, 30–35 %).

Among the Anseriformes (migrants and non-breeding birds) dominated: Branta leucopsis, Anser anser, Anas platyrhynchos, Anas (Mareca) penelope, Сlangula hyemalis, Bucephala clangula, Mergus serrator and Mergus merganser. The largest flocks were: Сlangula hyemalis (370) and Bucephala clangula (more than 600 birds per two days); they were recorded in Narva Bay and around Kurgalsky Reef mainly. Large flocks of Cygnus bewickii and C. cygnus were registered on 24.04.2016. Of all species of the order found, the Cygnus olor nests and broods turned out to be the most visible from aircraft: 13 nests were found in the Reserve area, and 6 were located on the Hangeloda Island on 26.05–2.06. 2020. The most numerous species from Charadriiformes order was Larus argentatus (up to 78 % of all gulls and terns). Large Larus argentatus and tern colonies were registered both on Kurgalsky Reef islets and the Reimosar Island. Of all species recorded, 19 are included into Red lists of different ranks (Table 4).

The Berezovye Islands archipelago is a Protected Area, Important Bird Area and Ramsar site too. This area covers 83, 9 km² and located in the northern part of the Gulf of Finland. Islands are separated from the mainland by the Bjorkezund Strait. During the observation days, very few birds were recorded on the archipelago compared to previous years of research: from 2500 in 2016 up to 1 240 birds in 2020 per two-day counts, with the main share being the numerous species of Larus argentatus (47.7 %) and Phalacrocorax carbo (25 %). So, for example, in the mid-90s of the 20th century, up to 20 000–30 000 swans, up to 70 000 brent geese, up to 1 million ducks of 18 species per season were observed here (Noskov, 1998); in 2000-2005 years 12 duck species, five gull species (1500–2000 pairs), three tern species (300–500 pairs) etc. bred here (Bublichenko, 2006, 2007a, Bublichenko, 2007b).

Nowadays, 15–18 species were only recorded here during each season counts compared to 40 species (excluding waders) recorded 20–30 years ago (Noskov, 1998; Bublichenko, 2006). It should be noted that 5–10 pairs of Larus fuscus only were recorded on the archipelago on observation days, whereas up to 400 pairs had been breeding here earlier (Bublichenko, 2007). Small flocks of Aythya fuligula, Сlangula hyemalis, Bucephala clangula and small stopovers of 3 swan species, Aythya ferina, Anas (Mareca) strepera, and two Merganser species were recorded on this area. However, 14 species of all the birds recorded are included into Red lists of different ranks (Table 4).

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Maly Tyuters, Bolshoi Tyuters, Bolshoi Fiskar, Southern and Northern Virgins and Seskar islands are the part of the «East of the Gulf of Finland» Federal Wildlife Reserve.

The Maly Tyuters Island is the most southwestern of the outer islands of the Gulf of Finland. (59.810 N, 26.9086 E). Northern part is covered with pine forests, a significant part – with sand dunes. Extensive coastline is covered with sandy beaches, rocky shoals and seaside meadows. Though, the published data about migratory birds of that region is scarce (Sagitov, 2012), most of the flocks are known to fly through the islands and water area in transit. During the observations, about 300 birds of 13 species were recorded in 2020, during the aerial survey in 2016–250 individuals of 7 species, in 2018 – 756 birds from 12 species. The largest flocks at water area and coastline were recorded in Anas platyrhynchos, Сlangula hyemalis, Bucephala clangula, Somateria mollissima, Mergus serrator, M. merganser, Larus argentatus; large Melanitta nigra and M. fusca flocks (more than 100-150 birds) were found on shallow waters far from the island (about 2 km to the West) in 2018–2020. Several Branta leucopsis and Anser anser flocks flew across the island by transit in 2016–2018. Several species started breeding here in 2020: Cygnus olor (one brood), Chroicocephalus ridibundus (at least 15–20 pairs) and Larus canus (5–7 pairs), Sterna hirundo (at least 20–25 pairs). Among birds protected in the region 9 species are included into Red lists of different ranks (Table 4).

The Bolshoi Tyuters Island (59.8605 N, 27.1945 E) is located approximately 15 km from the Maly Tyuters Island. It is a granite rock with an area of 8.3 km2, about 2.5 km across. Its main part is occupied by forests (mainly pine and spruce forests). There are few shallow waters around, the coastal is narrow, covered in places with sand, but for the most part – with stony placers. The spring migration of waterfowl has never been studied here before, and the observation of the autumn migration performed in 1996 (Buzun, 2006) suggests that the majority of migrants go through the water area by transit without stopping to rest or feed on the water. During the observation period the data were different: 304 (2016), 1 022 (2018) and 138 (2020) birds from 9 species were registered there, but the most of flocks (about 60–77 %) consisted of Phalacrocorax carbo, Larus argentatus and other gull species. Not numerous duck flocks and single Cygnus olor stopovers were recorded. Seven species registered here are included in the Red Data Books of different ranks (Table 4), but 3 species from them (geese) registered in 2016–2018 flew the island by transit.

Southern and Northern Virgin islands (59.9485 N, 26.8539 E) are two small islands, with a total area of 4 ha, located 1900 meters from each other. The shape of the islands is almost even circles, coastal ridges of pebbles. Coarse-grained sands and boulders are almost devoid of vegetation. Despite the small area, islands and surrounding shallow waters proved well suited to the rest and feeding of migratory waterfowl. During the aerial counts, up to 1000 birds/season of 10-15 species were recorded here. Larus argentatus were recorded on the South Virgin mainly, and single birds resting on the shore or rocks; but the North Virgin Island is densely populated: Phalacrocorax carbo, Сepphus grylle, Alca torda, Larus argentatus colonies, Anser anser, Cygnus olor, Сlangula hyemalis, Somateria mollissima small stopovers were registered annually. Сepphus grylle colony on the North Virgin Island is the only breeding site in this part of the Gulf of Finland. Bird number has increased several times in comparison with the number of the colony found here for the first time in 2007–2012 (Vysotsky, Verevkin, 2013). Seven out of the species registered here, are included into Red lists of different ranks (Table 4).

The Seskar Island (60.0230 N, 28.3777 E) is located 19 km from the southern mainland coast of the Gulf of Finland and has an area of 4.16 km2. The central part of the island is the highest and is covered with pine forests. There is a rocky shoal with an area of 8 km2 with less than 5 m depth at a distance up to 4–5 km to the west and north-west of the island; there are many small islets attracting birds not only during the seasonal migrations but also during the breeding period. The total number of birds recorded in the shallow water during the observation days was from 1500 individuals in 2016 (due to ice conditions and early surveys) up to 7700 in 2020; they were represented by 23–25 species. The most abundant species were Phalacrocorax carbo (more than 4300 birds in five large colonies were recorded in 2020), six Larus argentatus colonies (more than 500 pairs) and other Laridae and Sternidae species. We registered large stopovers of 10–14 Anseriformes species. Anser anser, Anas platyrhynchos, Сlangula hyemalis, Anas (Mareca) penelope, Bucephala clangula, Cygnus olor and

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C. cygnus, Mergus serrator, M. merganser, Melanitta nigra and M. fusca were the most numerous.

The number of species listed in the Red Data Books of different ranks is quite high: 15 (Table 4).

The Bolshoi Fiskar archipelago (60.4063 N, 27.9381 E) is located in the north-eastern part of the Gulf of Finland and consists of several small rocky islands with almost no vegetation. During the observation period, almost 3000 birds from four orders were recorded annually on the archipelago. We observed migratory flocks of 8 Anseriformes species and found two large cormorant colonies (at least 200 pairs) and European Herring Gull colonies (about 250–300 pairs). Anser anser, Branta leucopsis and Larus fuscus were not numerous, but we recorded them annually. Three white-tailed eagles at the same time was an interesting encounter on the archipelago in 02.06.2020 (Fig. 4). The only record (26.05.2020) of Hydroprogne caspia which is extremely rare in the Russian part of the Gulf of Finland nowadays is of interest. The number of species included into Red Data Books of different ranks is quite high too (16) (Table 4).

Koporskaya Bay – Chernaya Lakhta – Lebyazhy mainland coast is very important for migratory bird monitoring. The mainland in this area is completely covered with forests, in some places – with extensive swamps. Most of the coast line is covered with reed beds, in some places there are narrow sandy and rocky shoals. Koporskaya Bay has extensive shallows suitable for rest and feeding of birds. “Koporskaya Bay” is one of the 10 Important Bird Area (IBA) of the Gulf of Finland (Kondratyev, 2000), and “Lebyazhy” is also a regional reserve. Despite this fact, the summer fauna according to aerial surveys was represented only by small colonies of different gull and tern species, but during the spring migration, more than 1600–1900 birds of 21–24 species were recorded here annually. Gavia arctica, Ardea cinerea, Grus grus, Haematopus ostralegus, flocks of Podiceps cristatus, Casmerodius albus, Branta leucopsis, Сlangula hyemalis, Anas (Mareca) penelope, Bucephala clangula, Cygnus olor and C. cygnus, Fulica atra encounters are of interest. Besides, ten species of Anseriformes were recorded on the coast and water area. Seventeen species of all registered birds are included into the Red Data Books of different ranks (Table 4).

The Gogland Island (60.0660 N, 27.0000 E) is located 180 km west from Saint-Petersburg and 40 kilometers from Kotka. Its area is about 21 km2, height – up to 176 m. The surface of Gogland is formed by many rock massifs covered with coniferous forests; the coast is indented with many deep bays. The complex of breeding and migratory waterfowl and shorebirds is weakly represented due to a lack of overgrown and heated shallow water areas, with good feeding and protection conditions (Noskov, Gaginskaya, 2006); almost the entire coast is rocky area, which is not suitable for bird breeding either. Migratory flocks of geese, black geese, swans, cranes, loons cross the Gogland Island by transit from west to east at a considerable height in spring (Antipin, Gaginskaya, 2006). During the observation period, bird numbers fluctuated from 92 birds (2020) to 500–900 (2016–2018). In our opinion, such a large difference is due to the timing of the counts: surveys in 2020 were carried out late enough for the mass migration in this region. In 2016–2018 gulls and cormorants had the highest number (about 50 %). The most numerous was Larus canus (about 100-200 individuals annually). Small duck stopovers (Aythya fuligula, Mergus merganser, Bucephala clangula mostly) and Cygnus olor and C. cygnus stopovers were recorded in shallow waters. Of all species recorded here, seven are included into Red lists of different ranks (Table 4), but some of them are numerous usually during the migration in the Russian part of the Gulf of Finland (Aythya fuligula, for example).

Small rocky Rodsher Island (59.9679 N, 26.6797 E) with gently sloping rocky shores is located right on the border of the Leningrad Region (and about 500–700 m from the Russian border). It has the size less than 180 by 80 meters. The number of birds recorded during the observation period was large enough for such a small area – from 200 birds (2016) to 500–650 (2018–2020) of 6–11 species for each two-day aerial counts per season. In 2018–2020 the congregations of Alca torda (143 birds) sitting on stones near their colony were particularly noteworthy. Their number increased several times in comparison with the number of the colony found in 2007–2012 for the first time (Vysotsky, Verevkin, 2013). Stopovers of five duck species, Cygnus olor, Larus argentatus, terns were common here. In total, eight species registered on the island are included in the Red lists of different ranks (Table 4).

The Moshnyi Island (60.0093 N, 27.8486 E) is situated 40 km west of the Gogland Island. The area is 13.4 km2. The island consists of two parts connected by a narrow sandy isthmus. Both parts

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are low, strongly indented and overgrown with coniferous forest. Rugged shores of the island and numerous shallow waters make it attractive for migratory and breeding waterfowl and seabirds.

During the observation days, 1400 (2016)–8000 (2018) birds of 21–26 species were recorded on the coast and in the shallow waters area. The most numerous were cormorants (up to 17, 4 % of the total number of registered birds), Anseriformes birds (46, 3–57, 8 % in different years), gulls and terns (up to 26, 9 %). Сlangula hyemalis, Bucephala clangula, Somateria mollissima, scooters, Aythya fuligula had the largest stopovers here. Anser anser stopped in small flocks, usually no more than 8–12 birds (but their total number varied within 100–110 individuals annually). Larus argentatus colonies (up to 150 pairs) were found, 1–3 Cygnus olor pairs were recorded. The number of species listed in the Red Data Books of different ranks was 15 (Table 4).

The Maly island (60.0221 N, 28.0294 E) is located between Moshchny and Seskar islands, and six km east from the Moshchny island. The island is covered with forest, divided into three parts by narrow isthmuses. Isthmuses can be flooded when the water rises. The north coast is indented by many bays. Narrow coastline is predominantly sandy or sandy-stony. We registered about 1000– 2000 birds during the counts annually. It is interesting that the maximum number of birds was recorded in April, unlike other islands. 8–20 species were recorded in different years. Phalacrocorax carbo and Larus argentatus were the most numerous (up to 19 % and 8, 8 %, respectively). A lot of transit flocks were registered near the island on 13.05.2018: Branta bernicla, Anser anser, Anas (Mareca) penelope, scooters, mergansers. We fixed large stopovers of Bucephala clangula, swans (3 species) in 2020, Mergus merganser and Melanitta nigra – in 2018. The number of species listed in the Red Data Books of different ranks is 12 (Table 4).

The Kotlin Island (60.0118 N, 29.7336 E) is located 30 km west of the center of Saint-Petersburg. Its area is 16 km2. Kronstadt is situated in the eastern part of the island. The West Kotlin Nature Reserve of regional conservation significance is located on the western side of the island area. 4-6 species with a total number of 150–386 birds were noted on Kotlin Island annually. However, it is possible that a small number of birds recorded is due to the impossibility of their fixation among the aquatic and near-water vegetation.

The Vigrund Island (59.7799 N, 27.7442 E) is a little rocky island (1 hectare) located in 1.5 km from the coast of the Kurgalsky Peninsula. It is a cluster of the «East of the Gulf of Finland» Wildlife Reserve also. Four-six species (up to 220–240 birds) were registered on the Vigrund island and nearest shallows annually. We registered two breeding colonies here: Larus argentatus (up to 60 nests) and Phalacrocorax carbo (7–10 nests).

On Kotlin and Vigrund islands, no significant species diversity and high numbers of migrants and breeding birds were recorded during the aerial counts. But the total number of species registered during the observation period varied within 12 and 13, respectively. On both islands, gulls and cormorants accounted for up to 70–80 % of the total bird number. However, the number of species included into the Red Data Books of different ranks was five for the Kotlin and seven – for the Vigrund (Table 4).

We would like to emphasize that despite the differences in the accounting methods of other researchers in this area, the data obtained generally coincide both in the number of registered species (we mean only those species that are actually taken into account during aerial surveys) and in the migration sites and large bird colonies locations. So, for example, during the spring observations ten Anatidae species were registered on the Seskar Island (Rychkova, 2010), and during aerial surveys they varied from 10 to 14 in different years. There are no exact data on spring migrants in the materials justifying the creation of the Ingermanlandsky State Nature Reserve (later “Eastern Gulf of Finland” Wildlife Reserve), but the surveyed islands we listed are the most valuable for both migrants and breeding birds (Sagitov, 2012). The research indicates that large stopovers were observed in the shallow waters of Seskar, Maly Tyuters, Virgins, Long Stone islands. Especially numerous were Anas platyrhynchos, A. penelope, A. acuta, A. crecca, Aythya fuligula, Bucephala clangula, Clangula hyemalis, Melanitta nigra, M. fusca, Mergus merganser, M. serrator, geese, swans; gulls – Larus argentatus, L. canus, L. fuscus, Chroicocephalus ridibundus. Large breeding colonies of Phalacrocorax carbo, Larus argentatus and L. fuscus were registered on Seskar and Bolshoj Fiskar islands. Vulnerable avifauna species, listed in Red Books of various ranks, included

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30 species in all Russian islands investigated in 2010–2013 (Sagitov, 2012; Kouzov et al., 2013). The results of our research confirm these data. The data on the timing of waterbird migration, given by V. A. Buzun (2001), also correspond to the information obtained during our aerial surveys. The number of large bird species registered during ship-based surveys near the Russian islands of the Gulf of Finland on May, 20–24, 2013 was 43 (total number of species registered was 61, Kouzov et al., 2013), which also correlates with our data. The importance of Moschny and Seskar islands as well the “Kurgalsky” Nature Reserve as sites of mass stopovers is highlighted in this paper, which also corresponds to the data obtained.

However, from our point of view, it is incorrect to compare the number of species registered by different methods and with different duration of observations. So, there were mass stopovers of Anas acuta (≥ 4000) on the Seskar Island during the period 26.04.2005–7.06.2005 (Rychkova, 2010), but we did not observe this species in 2016–2020. At the same time, the total number of Bucephala clangula in 2005 was 1000 birds per season, but we registered 820 birds during 2 days only in May, 2020.

DISCUSSION AND CONCLUSION

Our results have shown some specific trends of locations of migratory bird stopovers and breeding avifauna diversity in studied area. Thus, based on the data obtained during the aerial surveys which we carried out within 3 years in the Russian part of the Gulf of Finland, it can be stated that there are 14 main sites of migratory bird stopovers in the surveyed area. Fifty three bird species from eight orders stop for resting and feeding here in spring annually. The largest sites of migratory bird stopovers are located near the Kurgalsky Peninsula, the Bolshoi Fiskar archipelago, around Moshnyi, Maly and Seskar islands, in the “Koporskaya Bay-Lebyazshy” mainland coast. The coastline and islands near the Kurgalsky Peninsula, the Berezovye Islands and Bolshoi Fiskar archipelagoes, Moshnyi, Seskar, Maly, Rodsher, North and South Virgins, Maly Tyuters islands and, to a much lesser extent — Bolshoi Tyuters, Gogland, Kotlin, Vigrund – are important for breeding waterfowl and shore birds too. The main locations of the migratory stopovers and the location of waterfowl and shorebirds colonies are shown in Figure 6. All these sites are very important for many rare species protected both in the Baltic region and Russia.

As a rule, birds fly by transit through the surveyed islands in mid – late April mainly, when the ice on the Gulf of Finland is not melted. The timing of the final destruction of the ice cover, which differs in different years, determines the beginning of mass migration. On the days of observation, the highest migratory activity was in mid-May.

Aerial photography showed the possibility of aerial counts of large nests both in colonies and single nests; our observations revealed that the most cormorants, mute swans and herring gulls started breeding in early May, first Cygnus olor broods were also clearly visible from the aircraft and were registered in beginning of June.

The data obtained revealed a sharp decrease in the number of migratory and breeding birds in the Berezovye Islands archipelago in comparison with previous years of observations (Noskov, 1998; Bublichenko, 2006, 2007a, Bublichenko 2007b). A serious negative impact on the biodiversity both migratory and breeding birds last years, on our opinion, is associated with the activities of two ports

– Primorsk and Vysotsk – located in close proximity to the Reserve. At the same time, the data obtained showed that the gas pipeline construction didn’t affect either the formation of migratory bird stopovers, or the composition and number of breeding birds of the islands of the Gulf of Finland and the “Kurgalsky” nature reserve. The rest of the surveyed sites had approximately the same species composition in all years of research (Sagitov, 2012; Kouzov et al., 2013; Shilin et al., 2014; our unpublished data). However, the number of migratory birds varied depending on the time of observation, weather conditions and the degree of ice melting.

Rare species included into the Red Data Books of various ranks were found on the Kurgalsky penninsula, the Koporskaya Bay, Moshnyi and Seskar islands, the Bolshoi Fiskar archipelago and on the Rondo Island (Berezovye Islands archipelago). It is necessary to emphasize a catastrophic decrease in the number of Larus fuscus in comparison with previous years of research (Noskov et

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al., 1995; Bublchenko, 2007b) as well as throughout the range of this species (Hario et al., 2004; Cherenkov et al., 2007; Varty, Tanner, 2009). The reasons of this problem are not completely clear, and can be associated both with natural population dynamics and with local deterioration of conditions in the breeding colonies areas, as it was mentioned above for the Berezovye Islands archipelago. However, an increase in the abundance of Alca torda and Uria aalge, which are rare in the Russian part of the Gulf of Finland, should also be noted.

Nowadays many changes in avifauna are mostly caused by the human activity. For the successful biodiversity conservation, it is necessary to monitor the most important sites both for breeding and migratory birds, to control and manage the processes of anthropogenic activities (construction, fishery, tourism etc.) in such a vulnerable ecosystem as the Gulf of Finland.

Acknowledgments. The observations were conducted with financial support from “Nord Stream 2 AG”, the project company established for planning, construction and subsequent operation of the Nord Stream 2 Pipeline, and JSC “Rosterminalugol”. Authors are grateful to S.V. Brilyakov for the help in collecting the photo material on May, 2020.

This study was performed in the frames of the state research project of Zoological Institute of RAS № 122031100282-2 (Russian Federation).

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  • статье представлены результаты трех сезонов весенних авиационных учетов птиц в российском секторе Финского залива Балтийского моря, в том числе, в акватории семи особо охраняемых природных территорий (ООПТ) – Государственного природного заповедника «Восток Финского залива», Государственного природного заказника «Березовые острова», Государственного природного комплексного заказника «Кургальский», Государственного природного комплексного заказника «Выборгский», регионального комплексного природного заказника «Котельский», регионального заказника «Лебяжий», регионального заказника «Западный Котлин». Основными целями проводившихся работ были мониторинг известных ранее и выявление новых мест концентрации морских, водоплавающих и околоводных птиц в период весенней миграции; уточнение мест расположения крупных гнездовых колоний в данном регионе, а также оценка возможности изменения их современной локации, численности и видового состава птиц в связи c постоянно растущей антропогенной нагрузкой на экосистему Финского залива. Авиаучеты птиц проводились в апреле–мае–начале июня 2016–2020 годов. Общее время наблюдений составило более 39 часов (около 4,5 часов в день). Учеты проводились дважды за весенний период в 2016 и 2020 годах и четыре раза – весной 2018 года, с интервалом в 5–7 дней для получения более полных данных об изменениях в составе и численности птиц на миграционных стоянках, местах их расположения и фиксации начала размножения. В период наблюдений было зарегистрировано 81 509 птиц 53 видов из 8 отрядов; из них 24 вида включены в Красные книги разного ранга. При обработке первичного материала было проанализировано 18 066 фотографий, сделанных с борта самолета. Полученные данные показали, что во время весенней миграции в обследованном районе насчитывается 15 основных стоянок водоплавающих и околоводных птиц; также было выявлено 9 участков их массового размножения. Авиаучеты 2016–2020 позволили составить более полную картину о современной ситуации на весенних миграционных стоянках и местах размножения птиц на Финском заливе. Следует отметить, что столь детальные авиаучеты птиц на обширных участках акватории проводились впервые в этом регионе.

Ключевые слова: весенняя миграция, весенние миграционные стоянки, водоплавающие птицы, околоводные птицы, колония, размножение.

Поступила в редакцию 10.09.23

Принята к печати 04.10.23

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