In the source and the upper reaches of the Angara river there is a very large «cold» wintering shorebirds and waterfowl - up to 32.0 thousand individuals. In the period of autumn migration, there are large gulls here, fairly characteristic of this region: the Mongolian Gull Larus (vegae) mongolicus, the Common Gull L. canus, the East Siberian L. vegae, occasionally the Black-headed L. ridibundus, the Little L. minutus gulls and, very rarely, Heuglin’s Gull L. heuglini. The most common, and at times numerous species during wintering, are Mongolian and Common Gulls, while the rest of their species are always rare (they are not found every year) and are few. The formation of a «cold» wintering on this site of Baikal is due to the existence of coastal thermal refugiums, as well as some features of the biology and migration of different species of the birds. The dynamics of the number of large white-headed gulls in this area of Southern Baikal from the middle of the past century (1972) to the present is traced. The number of birds staying for the winter at the source of the Angara river are determined by weather conditions on the paths of their passage and the mass of the last wave of migration. A very high abundance of this wave is observed during the years of high summer death of clutches, usually associated with strong fluctuations in water level, when floodplains are completely flooded. In such years, the number of repeated (compensation) clutches sharply increases due to the high death of nests and the proportion of late broods of waterfowl increases. They begin to fly late and the timing of bird migration to the southern wintering places is shifted to a very late time. In addition, such birds have a very small reserve of time, which they can use to accumulate the necessary amount of energy resources (fat) necessary for a long flight. Therefore, they fly with short migratory throws, often stopping in favorable places for rest and replenishment of energy resources (Dolnik, 1975). Favorable conditions (weather and feed) in the source and upper reaches of the Angara river contribute to the long delay of birds to replenish energy resources. However, by the time they physiologically become able to make a long migration throw, migration is already impossible: almost all water bodies freeze, permanent snow cover, low air temperatures are established, and mountain passes, due to strong winds, become insurmountable. Birds are forced to stay here for the winter. Consequently, a large thermal refugium at the source of the Angara river become an ecological trap for birds, and the «cold» wintering itself is compelled. During the wintering season, the number of birds remaining here decreases very quickly - from a few hundred to 7-12, and at the last stages of wintering and single individuals. In the last decade, characterized by the strongest warming, successful experiences of the winter period have been established by independent individuals of the Mongolian gull. Details are considered the causes of this phenomenon.

Mel’nikov Yuriy Ivanovich, Candidate of Sciences (Biology), Head of Postgraduate Studies, Baikal Museum ISC SB RAS, 1, Akademicheskaya st., Listvyanka Settl., Irkutsk Region, 664520, Russian Federation, tel.: (3952) 45–31–45, e-mail: yumel48@mail.ru

Mel’nikov Yu.I. White-headed Gulls on the «Cold» Wintering in the Source and Upper Flow of Angara River: Formation of Winter Aggregations and Survival Conditions. The Bulletin of Irkutsk State University. Series Biology. Ecology, 2019, vol. 27, pp. 41-61. https://doi.org/10.26516/2073-3372.2019.27.41 (in Russian)

Atlas Irkutskoi oblasti. [Atlas of Irkutsk Region]. Moscow. Irkutsk, GUGiK Publ., 1962, 182 p. (in Russian)

Baikal. Atlas. [Lake Baikal. Atlas]. Moscow, Roskartografiya Publ., 1993, 160 p. (in Russian)

Bol'shakov K.V. Rekonstruktsiya polnoi kartiny nochnogo proleta ptits i effektivnost' obnaruzheniya ee razlichnymi metodami [Reconstruction of the full picture of the night flight of birds and the effectiveness of its detection by various methods]. Metody obnaruzheniya i ucheta migratsii ptits [Methods for detecting and recording migrations of birds]. Leningrad, Nauka Publ., 1981, pp. 95-122. (in Russian)

Zherebtsov G.A., Kovalenko V.A., Molodykh S.I., Kirichenko K.E. Vliyanie solnechnoi aktivnosti na temperaturu troposfery i poverkhnosti okeana [The influence of solar activity on the temperature of the troposphere and ocean surface]. Bull. Irkutsk St. Univ. Ser. Earth Sci., 2013, vol. 6, no 1, pp. 61-79. (in Russian)

Voronin V.I., Khantemirov R.M., Naurzbaev M.M. Sverkhdlinnye sibirskie drevesnokoltsevye khronologii – nadezhnye arkhivy dlya paleoklimaticheskikh rekonstruktsii [UltraLong Siberian Tree-Ring Chronologies – Reliable Archives for Paleoclimatic Reconstructions]. Razvitie zhizni v protsesse abioticheskikh izmenenii na Zemle [Development of Life on Earth during Abiotic Changes: Proc. Sci. Conf., Irkutsk, Russia]. Irkutsk, V. B. Sochava Inst. of Geography SB RAS Publ., 2014, pp. 409-415. (in Russian) 

Gagina T.N. Vodoplavayushchie ptitsy, zimuyushchie v Pribaikalie [Waterfowl wintering in the Baikal region]. Bul. Irkutsk Agric. Inst., 1958, vol. 8, pp. 114-129. (in Russian)

Galazii G.I. Baikal v voprosakh i otvetakh [Baikal in questions and answers]. Irkutsk, EastSib. Book. Publ., 1984, 367 p. (in Russian)

Galazii G.I. Baikal v voprosakh i otvetakh [Baikal in questions and answers]. Irkutsk, Forvard Publ, 2012, 320 p. (in Russian)

Dol'nik V. R. Migratsionnoe sostoyanie ptits [Migratory state of birds.]. Moscow, Nauka Publ., 1975, 398 p. (in Russian)

Dybovskii B., Godlevskii V. Otchet o zanyatiyakh v 1876 g. [Report on occupations in 1876]. Izv. Sib. otd-nija IRGO [Bul. Sib. Br. Imper. Rus. Geogr. Soc.]. Irkutsk, 1877, vol. 8, no 3-4, pp. 1117-1123. (in Russian)

Zherebtsov G.A., Kovalenko V.A., Molodykh S.I., Rubtsova O.A. Zakonomernosti klimaticheskikh izmenenii v XX v. i osnovnye fizicheskie protsessy, otvetstvennye za eti izmeneniya [Patterns of climate change in the XX century. and the basic physical processes responsible for these changes]. Bull. Irkutsk St. Univ. Ser. Earth Sci., 2011, vol. 4, no. 1, pp. 87-108. (in Russian)

Zaks L. Statisticheskoe otsenivanie [Statistical evaluation]. Moscow, Statistika Publ., 1976, 599 p. (in Russian)

 Kochugova E.A. Izmenchivost' zimnikh minimalnykh temperatur vozdukha v Predbaikal'e [Variability of winter minimum air temperatures in Cisbaikalia]. Bull. Irkutsk St. Univ. Ser. Earth Sci., 2015, vol. 13, pp. 98-110. (in Russian)

Krivenko V.G. Vodoplavayushchie ptitsy i ikh okhrana [Waterfowls and their Protection]. Moscow, Agropromizdat Publ., 1991, 271 p. (in Russian) 

Latysheva I.V., Loshchenko K.A., Shakhaeva E.V. Issledovaniya dinamiki Aziatskogo antitsiklona i kholodnykh tsirkulyatsionnykh periodov na territorii Irkutskoi oblasti [Studies of the dynamics of the Asian anticyclone and cold circulation periods in the territory of the Irkutsk region]. Bull. Irkutsk St. Univ. Ser. Earth Sci., 2011, vol. 4, no 2, pp. 161-171. (in Russian)

Mel'nikov Yu.I. Pozdneosennii prolet krupnykh chaek v Verkhnem Priangar'e [Late autumn flight of large gulls in the Upper Angara region]. Bull. Irkutsk St. Agric. Acad., 1997, vol. 4, pp. 34-36. (in Russian)

Mel'nikov Yu.I. Kholodnye zimovki vodoplavayushchikh i okolovodnykh ptits v verkhnem techenii Angary: sovremennyi status, sostoyanie i okhrana [Cold winterings of waterfowl and shore birds in the upper reaches of the Angara: current status, status and protection]. Rus. Ornitol. Zhurn., 2000a, no 109, pp. 16-20. (in Russian)

Mel'nikov Yu.I. Osobennosti ucheta chislennosti vodoplavayushchikh ptits na angarskikh zimovkakh [Features of accounting for the number of waterfowl in the Angara wintering grounds]. Inventarizatsiya, monitoring i okhrana klyuchevykh ornitologicheskikh territorii Rossii: Materialy soveshch. po programme «Klyuchevye ornitologicheskie territorii Rossii» (1998–2000 g.) [Inventory, monitoring and protection of key ornithological territories of Russia: Proc. Meet., Moscow, Russia]. Moscow, SOPR Publ., 2000b, vol., 2, pp. 33-40. (in Russian)

Mel'nikov Yu.I. Populyatsionnyi gomeostaz v reproduktivnyi period (na primere okolovodnykh i vodoplavayushchikh ptits) [Population homeostasis in the reproductive period (for example, shorebirds and waterfowl]. Razvitie sovremennoi ornitologii v Severnoi Evrazii: Tr. XII mezhd. ornitol. konf.) [Development of Modern Ornithology in Northern Eurasia: Proc. Int. Conf., Stavropol, Russia)]. Stavropol, Stavropol St. Univ. Publ., 2006, pp. 316-334. (in Russian)

Mel'nikov Yu.I. Klyuchevaya ornitologicheskaya territoriya mezhdunarodnogo znacheniya: Istok i verkhnee techenie r. Angary [Key ornithological territory of international importance: Source and up stream of Angara river]. Baikal. Zool. Zhurn., 2010a, no. 1(4), pp. 41-46. (in Russian)

Mel'nikov Yu.I. Khishchnichestvo chaikovykh ptits v delte r. Selenga (Yuzhnyi Baikal): novaya troficheskaya strategiya v izmenchivykh usloviyakh sredy [Predatory gull birds in the delta. Selenga (South Baikal): a new trophic strategy in a changing environment]. Bull. Irkutsk St. Agric. Acad., 2010b, vol. 41, pp. 57-69. (in Russian)

Mel'nikov Yu.I. Kompensatsionnoe razmnozhenie okolovodnykh i vodoplavayushchikh ptits: vydelenie povtornykh kladok na osnove materialov polevykh nablyudenii [Compensatory reproduction of shorebirds and waterfowl: allocation of repeated clutches on the basis of field observation materials]. Bull. Irkutsk. St. Univ. Ser. Biol. Ekol., 2011, vol. 4, no. 3, pp. 41-53. (in Russian)

Mel'nikov Yu.I. Izbiratel'naya eliminatsiya samok gogolya Bucephala clangula na «kholodnykh» zimovkakh v verkhnem techenii r. Angary (Vostochnaya Sibir') [Selective elimination of Goldeneye Bucephala clangula females in cold winters in the upper course of the Angara river (Eastern Siberia)]. Bull. Irkutsk St. Univ. Ser. Biol. Ekol., 2012, vol. 5, no. 2, pp. 32-43. (in Russian)

Mel'nikov Yu.I. Izmeneniya v povedenii i ekologii vodoplavayushchikh ptits na «kholodnykh» zimovkakh v verkhnem techenii r. Angara v nachale XXI stoletiya [Changes in the behavior and ecology of waterfowl on the «cold» wintering in the upper reaches of the Angara river at the beginning of the XXI century]. Bull. Irkutsk St. Agric. Acad., 2013a, vol. 57, p. 2, pp. 29-36. (in Russian)

Mel'nikov Yu.I. Vechernii otlet gogolei, zimuyushchikh v istoke r. Angara, na nochevku v Baikal: novyi vzglyad na staruyu problemu [Evening departure Goldeneye, wintering at the source of the Angara river to spend the night in Baikal: a new look at the old problem]. Sovremennye problemy ornitologii Sibiri i Tsentralnoi Azii [Modern problems of ornithology in Siberia and Central Asia]. Ulan-Ude, Buryat St. Univ. Publ., 2013b, pp. 214-219. (in Russian)

Mel'nikov Yu.I. Pozdneosennii prolet okolovodnykh i vodoplavayushchikh ptits i ego rol' v formirovanii «kholodnykh» zimovok Verkhnego Priangar'ya [Late autumn flight of Shorebirds and Waterfowl and its role in the formation of “cold” winters of the Upper Angara region]. Baikal. Zool. Zhurn., 2014a, no. 1(14), pp. 69-84. (in Russian)

Mel'nikov Yu.I. «Kholodnye» zimovki obyknovennogo gogolya Bucephala clangula (Linnaeus, 1758) (Aves, Anatidae) Verkhnego Priangar'ya: formirovanie i dinamika v sovremennykh klimaticheskikh usloviyakh [«Cold» wintering of the Common Goldeneye Bucephala clangula (Linnaeus, 1758) (Aves, Anatidae) of the Upper Angara region: formation and dynamics in modern climatic conditions]. Razvitie zhizni v protsesse abioticheskikh izmenenii na Zemle [The development of life in the process of abiotic changes on Earth: Proc. Sci. Conf., Irkutsk, Russia]. Irkutsk, V.B. Sochava Inst. of Geography SB RAS Publ., 2014b, pp. 164-169. (in Russian)

Mel'nikov Yu.I. Utochnenie k uchetu vodoplavayushchikh ptits s berega na «kholodnoi» zimovke v istoke r. Angary [Refinement to the accounting of waterfowl from the shore in a «cold» wintering at the source of the Angara river]. Baikal. Zool. Zhurn., 2016a, no. 1(18), pp. 58-60. (in Russian) 

Mel'nikov Yu.I. Sovremennaya fauna ptits kotloviny ozera Baikal i osobennosti ee formirovaniya [The modern bird fauna of the basin of Lake Baikal and the features of its formation]. Bull. Irkutsk St. Univ. Ser. Biol. Ekol., 2016b, vol. 16, pp. 62-83. (in Russian)

Mel'nikov Yu.I. Novye vidy ptits kotloviny ozera Baikal: analiz vidovoi i ekologicheskoi struktury [New bird species in the Baikal basin: analysis of the species and ecological structure]. Bull. Irkutsk St. Univ. Ser. Biol. Ekol., 2018, vol. 24, pp. 25-48. (in Russian). https://doi.org/10.26516/2073-3372.2018.24.25 

Mel'nikov Yu.I., Shcherbakov I.I., Testin A.I. Sovremennoe sostoyanie zimovki okolovodnykh ptits v istoke r. Angary [The current state of wintering of Shorebirds at the source of the Angara river]. Promyslovye zhivotnye i povyshenie effektivnosti proizvodstva okhotnichiego khozyaistva [Commercial animals and improving the efficiency of hunting production]. Irkutsk, Irkutsk Agricult. Inst. Publ., 1988, pp. 65-72. (in Russian)

Mel'nikov Yu.I., Shcherbakov I.I., Testin A.I. Otsenka tochnosti uchetov chislennosti plastinchatoklyuvykh ptits [Estimation of the accuracy of counting the number of plate-beaked birds]. Vsesoyuznoye soveshchanie po probleme kadastra i ucheta zhivotnogo mira [All-Union Meet. on the Issue of Cadastre and Wildlife Management: abstracts of the report, Ufa, Russia]. Ufa, Bashkir. Book. Publ., 1989, part 1, pp. 394-395. (in Rissian)

Mel'nikov Yu.I., Shcherbakov I.I. Sistema kontrolya za sostoyaniem zimovok vodoplavayushchikh ptits verkhnego techeniya r. Angary [Monitoring system for the wintering conditions of waterfowl in the upper reaches of the Angara river]. Vsesoyuznoye soveshchanie po probleme kadastra i ucheta zhivotnogo mira [All-Union Meet. on the Issue of Cadastre and Wildlife Management. Abstracts of the report, Ufa, Russia]. Ufa, Bashkir. Book Publ., 1989, part 2, pp. 360-362. (in Rissian)

Mel'nikov Yu.I., Popov V.V., Zhovtyuk P.I. Pervyi opyt ispolzovaniya SVP «KhIVUS-10» dlya ucheta vodoplavayushchikh ptits na «kholodnoi» zimovke v istoke r. Angary [The first experience of using HIVUS-10 hovercraft to record for waterfowl during cold wintering at the source of the Angara river]. Baikal. Zool. Zhurn., 2012, no. 1(9), pp. 5-10. (in Russian)

Mel'nikov Yu.I., Popov V.V., Zhovtyuk P.I. Rezultaty vesennego ucheta (s ispol'zovaniem SVP «KhIVUS-10») okolovodnykh i vodoplavayushchikh ptits na «kholodnoi» zimovke v istoke r. Angary v 2014 g. [The results of the spring survey (using the HIVUS-10 SVP) of Shorebirds and waterfowl on the «cold» wintering at the source of the Angara river in 2014]. Baikal. Zool. Zhurn., 2015, no. 1(16), pp. 103-106. (in Russian)

Mel'nikov Yu.I., Popov V.V., Zhovtyuk P.I. Chislennost', vidovoi sostav i raspredelenie okolovodnykh i vodoplavayushchikh ptits na «kholodnoi» zimovke v istoke r. Angary vesnoi 2016 g. [The number, species structure and distribution of shorebirds and waterfowl in the «cold» wintering at the source of the Angara river in spring 2016]. Baikal. Zool. Zhurn., 2016, no. 2(19), pp. 81-83. (in Russian)

Mel'nikov Yu.I., Popov V.V., Zhovtyuk P.I. Osobennosti raspredeleniya vodoplavayushchikh ptits na «kholodnoi» zimovke v istoke i verkhnem techenii r. Angary (Yuzhnyi Baikal) v sovremennyi period [Features of the distribution of waterfowl in the «cold» wintering in the source and upstream of the Angara river (Southern Baikal) in the modern period]. Baikal. Zool. Zhurn., 2017, no. 2(21), pp. 67-74. (in Russian)

Mel'nikov Yu.I., Popov V.V., Zhovtyuk P.I. Vodoplavayushchie ptitsy na «kholodnoi» zimovke v istoke i verkhnem techenii r. Angary: uchet s berega, effektivnaya shirina uchetnoi polosy i tochnost' poluchennykh dannykh [Waterfowl on the «cold» wintering in the source and the upper reaches of the Angara river: accounting from the shore, the effective width of the accounting band and the accuracy of the data]. Baikal. Zool. Zhurn., 2019, no. 1(24), pp. 60-73. (in Russian)

Pastukhov V.D. Nablyudenie za angarskoi zimovkoi vodoplavayushchikh ptits [Observation of the angara wintering of waterfowl]. Konf. mol. uchenykh, posvyashch. pamyati G. Yu. Vereshchagina [Sci. Conf. in Mem. G. Yu. Vereshchagin: Irkutsk, Russia]. Irkutsk, Limnol. Inst. SB RAN Publ., 1961, pp. 23-26. (in Russian)

Batmunkh D., Nyambayar B., Bukhaim A., Tuvshinzhargal E., Otgonbayar Ts., Zhugdernamzhil N., Tseveenmyadag N., Tuvshintugs S. Predvaritelnye rezultaty koltsevaniya ptits v Severo-Vostochnoi Mongolii [Preliminary bird ringing results in Northeast Mongolia]. Sovremennye problemy ornitologii Sibiri i Tsentral'noi Azii: materialy VI mezhdun. ornitol. konf. (18 oktyabrya 2018 g., Irkutsk, Rossiya) [Modern problems of ornithology in Siberia and Central Asia: Proc. Int. Conf., Irkutsk, Russia]. Irkutsk, INCHT Publ., 2018, pp. 42-43. (in Russian)

Pronin N.M. Ryby ozera Baikal i ego basseina [Fish of Lake Baikal and its basin]. Ulan-Ude: BSC SB RAS Publ., 2007, 284 p. (in Russian)

Mel'nikov Yu.I., Zhovtyuk P.I., Popov V.V., Tupitsyn I.I. Rannevesennii uchet okolovodnykh i vodoplavayushchikh ptits v istoke i verkhnem techenii r. Angary v 2017 g. s ispolzovaniem SVP «KhIVUS-10» [Early spring accounting of shorebirds and waterfowl in the source and upstream of the Angara river in 2017 using the HIVUS-10 SVP]. Baikal. Zool. Zhurn., 2017, no. 1(20), pp. 53-56. (in Russian)

Fefelov I.V., Alekseenko M.N., Ryabtsev V.V., Olovyannikova N.M. Rezul'taty ucheta zimuyushchikh vodoplavayushchikh ptits v raione istoka Angary s berega v 2014-2017 gg. [The results of the accounting of wintering waterfowl in the area of the Angara source from the coast in 2014-2017]. Priroda Baikal'skoi Sibiri. Tr. zapovednikov i nats. parkov Baikalskoi Sibiri [Nature of Baikal Siberia. Proc. Nature Reserves and National Parks of the Baikal Siberia]. Ulan-Ude, BSC SB RAS Publ., 2017, vol. 2, pp. 179-189. (in Russian)

Skryabin N.G. Vodoplavayushchie ptitsy Baikala [Baikal Waterfowl]. Irkutsk, EastSib. Book Publ., 1975. 244 p. (in Russian)

Tarasov P.P. O zimovkakh vodoplavayushchikh ptits na Baikale [About wintering waterfowl on Baikal]. Priroda, 1952, no. 8, pp. 115-116. (in Russian)

Tret'yakov A.V. Ptitsy, zimuyushchie v istokakh r. Angary [Birds wintering in the source of the Angara river]. Ornitofauna Kalininskoi oblasti [Ornitofauna of the Kalinin region]. Kalinin, Kalinin St. Pedag. Inst. Publ., 1940, pp. 61-71. (in Russian)

Fefelov I.V., Ryabtsev V.V., Tupitsyn I.I. Chislennost' zimuyushchikh utok v verkhov'yakh Angary v 2000-kh gg. [The number of wintering ducks in the upper reaches of the Angara river in the 2000-s.]. Kazarka, 2008, vol. 11, no. 1, pp. 92-106. (in Russian)

Mel'nikov Yu.I., Popov V.V., Tupitsyn I.I., Zhovtyuk P.I. Chislennost', vidovoi sostav i raspredelenie okolovodnykh i vodoplavayushchikh ptits na «kholodnoi» zimovke v istoke r. Angary v ekstremal'no teplyi sezon 2014-2015 gg. [The number, species composition and distribution of waterbirds and waterfowl in the «cold» wintering at the source of the Angara river in the extremely warm season of 2014-2015]. Baikal. zool. zhurn., 2016, no. 1(18), pp. 89-98. (in Russian) 

Shimaraev M. N., Kuimova L. N., Sinyukovich V. N. Tendentsii izmeneniya abioticheskikh uslovii v Baikale v sovremennyi period [Trends in abiotic conditions in Baikal in the modern period]. Razvitie zhizni v protsesse abioticheskikh izmenenii na Zemle: materialy I nauchno-praktich. konf. (18-20 marta 2008 g., Listvyanka, Rossiya) [The development of life in the process of abiotic changes on Earth: Proc. Sci. Conf., Listvyanka, Russia]. Novosibirsk, SB RAN Publ., 2008, pp. 311-318. (in Russian) 

Shimaraev M.N., Starygina L.N. Zonalnaya tsirkulyatsiya atmosfery, klimat i gidrologicheskie protsessy na Baikale (1968-2007 gg.) [Zonal atmospheric circulation, climate and hydrological processes on Baikal (1968-2007)]. Geography and Natural Resources, 2010, no. 3, pp. 62-68. (in Russian)

Georgi J.G. Bemerkungen einer Reise im Russischen Reich im Jahre 1772. St.-Petersb.: Kayserl. Academie der Wissenschaften, 1775, bd. 2, 920 s.

Taczanowski L. Faune ornithologique de la Siberie Orientale. Memoires de l’Academie imperale des sciences de Saint-Petersburg, 1893, vol. 39, no. 7, 1278 p.