Tsvelych_02_2022.indd UDC 598.243.8(262.5) DISTRIBUTION OF SIBLING SPECIES YELLOW-LEGGED GULL, LARUS MICHAHELLIS AND CASPIAN GULL, LARUS CACHINNANS (CHARADRIIFORMES, LARIDAE), ON THE BLACK SEA COAST A. N. Tsvelykh Schmalhausen Institute of Zoology, NAS of Ukraine, vul. B. Khmelnytskogo, 15, Kyiv, 01030 Ukraine E-mail: TSV@izan.kiev.ua A. N. Tsvelykh (https://orcid.org/0000-0001-8970-5477) Distribution of Sibling Species Yellow-legged Gull, Larus michahellis and Caspian Gull, Larus cachinnans (Charadriiformes, Laridae), on the Black Sea Coast. Tsvelykh, A. N. — Distribution of sib- ling species Larus cachinnans (Pallas, 1811) and Larus michahellis (J. F. Naumann 1840) were studied on coast of the Black Sea. Originally, Larus michahellis breeds on seaside cliff s and rocky islets of the Southern part of the Black Sea and of the Crimean Peninsula. Having adapted to breeding on the roofs of buildings, this species is spread to the north along the seaside: to Novorossiysk on the eastern coast, to Constanta on the western one. Additionally, an isolated population of Larus cachinnans breeds on low-lying islands and sand spits mostly in the Northwestern Black Sea. Here, the species spreads on the seaside from Constanta northward to Karkinitian Bay. Further to the east, breeding populations of Caspian Gull are found on the Black Sea coast only at the southeastern edge of the Taman Peninsula to the south to Anapa. Th e coast of the Sea of Azov, adjacent to the northeastern part of the Black Sea, is densely populated by Larus cachin- nans. Only in the southern part of the Sea of Azov, on the coast of the Kerch Peninsula, there is a small population of Larus michahellis. K e y w o r d s: Larus michahellis, Larus cachinnans, sibling species, distribution, expansion, Black sea. Introduction Until recently, it was believed that Larus cachinnans, of the superspecies “herring gull” complex, was widespread in the Mediterranean and the Black Sea region. However, large-scale genetic studies of gulls of that complex have shown that Larus michahellis is spread in the Mediterranean and the adjacent Atlantic regions (Liebers et al., 2004). It was previously considered as a subspecies of Larus cachinnans. Both species are found in the Black Sea region. Th e estimated range of Larus michahellis in the Black Sea is limited to its southwestern coast, and Larus cachinnans is widespread in the northwestern, northern and most of the eastern Black Sea region according to maps based on the genetic studies (Liebers et al., 2004; Liebers-Helbig et al., 2010). In the latest report on the world’s birds (del Hoyo et al., 2014), the range of Larus michahellis also covers most of the southern coast of the Black Sea, and the range of Larus cachinnans is limited to its northwestern and northern coasts. At the same time, no gull populations were shown at the southeastern coast of the Black Sea and the sea coast of the Crimean Peninsula, which is completely untrue. In addition, the recent discovery of a large population of Larus michahellis on the Crimean Peninsula (Tsvelykh, 2016; Sikorsky, 2016; Tsvelykh, 2018) and the currently observed dispersal of this species on the Black Sea coast to the north radically change the confi guration of the ranges of these sibling species on the Black Sea coast. Th e aim of this work was to investigate the current distribution of L. cachinnans and L. michahellis on the Black Sea coast. Zoodiversity, 56(2):165–170, 2022 DOI 10.15407/zoo2022.02.165 Ornithology 166 A. N. Tsvelykh Material and methods Th e author analyzed his own and published data on the distribution of L. michahellis and L. cachinnans in the Black Sea region. Th e results of the analysis of gull specimens collected at the Black Sea coast and stored in the funds of the Zoological Museum of Taras Shevchenko National University of Kyiv and the National Museum of Natural History of the National Academy of Sciences of Ukraine are used. Th e species L. cachinnans and L. michahellis were discriminated by the peculiarities of the coloration of primaries (Garner, Quinn, 1997; Gibbins et al., 2010). Adult L. michahellis is easily distinguished from L. cachinnans by the presence of an extensive black area between the white preapical spot and the white "tongue" on the inner vane of the outer (10th) primaries (fi g. 1). In Larus cachinnans, the length of the black area between the edge of the white “tongue” on the inner vane of the outer primaries and the edge of the white preapical spot does not exceed the length of the white spot measured from the tip of the feather, but is almost twice as long in L. michahellis (Tsvelykh, 2016). Th e same is true for the 9th primaries. In addition, the white preapical spot on the 9th primaries, which is always present in the Caspian Gull (fi g. 1, B, D), is absent in the Yellow-Legged Gull part (fi g. 1, A, C), therefore all such birds are undoubtedly L. michahellis. Results and discussion L. michahellis is distributed throughout the southern coast of the Black Sea in Tur- key (Kirwan et al., 2008; Sozen et al., 2015). Obviously, the Yellow-legged Gull has long populated the southeastern Black Sea areas adjacent to the Turkish coast. On the Black Sea coast of Georgia, a large colony of “herring gulls” has long been known at the mouth of the Chorokhi River, near Kobuleti town, which is 20 km north of Batumi City (Boehme et al., 1987). Th e identifi cation of those gulls as L. michahellis is proved by the analysis of mu- seum specimens. Th e collection of the National Museum of Natural History of the National Academy of Sciences of Ukraine contains four gulls specimens caught in the same area, in Churuksu (the former name of Kobuleti) in the summer of 1910. Two adult birds in defi ni- tive plumage that were caught there on August 20, 1910 (fi g. 1, A) and September 9, 1910 plainly belong to the species L. michahellis. Fig. 1. Diff erences in coloration of the outer primaries of Larus michahellis (left column) and Larus cachinnans (right column) from the Black Sea coast. A — Kobuleti, Georgia. August 20, 1910 (collection of the National Museum of Natural History, the National Academy of Sciences of Ukraine), B — Karadag, Crimean Peninsula, Ukraine, July 2, 1946; (collection of the Zoological Museum of Kyiv National University), C — Vilkovo, Danube Delta, Ukraine, April 26, 1948 (collection of the Zoological Museum of Kyiv National University), D — Swan Islands, Karkinitian Bay, Ukraine, February 22, 1972 (collection of the National Museum of Natural History of the National Academy of Sciences of Ukraine). A C B D 167Distribution of Sibling Species Larus michahellis and Larus cachinnans on the Black Sea Coast Apparently, at the beginning of the XXI century, L. michahellis began to spread along the eastern coast of the Black Sea to the north. In 2008, V. I. Malandzia found L. michahellis nesting on the ru- ins of tall buildings off the coast of Abkhazia in northwestern Georgia (Belik, 2013). In 2014 and 2015, breeding of L. michahellis was re- corded further north, on the Black Sea coast of Russia. Th e birds bred on the roof of a building in the sea- side city of Sochi (Til’ba, Filipov, 2016). In 2018, a large colony of L. michahellis was discovered even further north, in the seaside City of Novorossiysk (Belik, 2018). Th e birds bred on the fl at roofs of the buildings. Along the western coast of the Black Sea, L. michahellis is distributed up to the city of Constanta in Romania to the north; all the gulls collected there, according to analysis of mitochondrial DNA, belonged to that species (Liebers et al., 2004). It should be noted that L. michahellis breeding in Constanta was known before. R. Klein and A. Buchheim (1997) found that gulls breeding on roofs of building in Constanta diff ered in plumage and struc- tural characters from those breeding on temporary islets in coastal lagoons 50 km north of town. Roof-top breeders corresponded closely to the phenotype of L. michahellis, whereas lagoon breeders corresponded mostly to L. cachinnans. Roof-top breeders have been known in Romania and Bulgaria for over 100 years (Nankinov at al., 1997; Klein, Buchheim, 1997). Due to the obvious tendency of L. michahellis to spread along the western coast of the Black Sea, breeding in cities, it is necessary to discuss reports indicating the breeding of this spe- cies far north of Constanta, in the City of Odesa in Ukraine. In 2011, a nest of L. cachinnans was found in Odesa on the rooft op of a building (Rusev et al., 2011). Apparently, gulls bred there in 2009 as well (Rusev et al., 2011). Subsequently, it was suggested that these gulls were L. michahellis (Panchenko et al., 2015). Th e authors (Panchenko et al., 2015) referred to the personal communication of N. S. Atamas, who determined the gull species by the provided photographs. However, I failed to fi nd out what criteria were used for the spe- cies identifi cation of gulls, and the photographs, as it turned out, were subsequently lost (N. S. Atamas, personal communi- cation; P. S. Panchenko, personal communication). Dr. I. T. Rusev kindly provided me for analysis with photographs taken by him at the gull nest in Odesa in 2011. Th e quality of the photographs was good enough to distinguish an ex- tensive black gap between the inner edge of the white pre-apical spot and the end of the light "tongue" on the inner vane of the outer pri- maries of the gull’s wing (fi g. 2). Its length was almost twice the length of the white preapical spot, which indicates (see above) that this bird belongs to the species Larus micha- Fig. 2. Th e Gull nesting on the roof of the building in Odesa. June 7, 2011. Photo by I. T. Rusev. Fig. 3. Th e northernmost breeding point of Larus michahellis on the Black sea coast. A Yellow-legged Gull chick in a nest on the roof of the building in Odesa. June 7, 2011. Photo by I. T. Rusev. 168 A. N. Tsvelykh hellis. Also, a number of additional features can be seen in the photograph with suffi cient magnifi cation. Although not individually diagnostic, they make it possible to distinguish most Larus michahellis from Larus cachinnans if combined with other features (Gibbins et al., 2010). Th ose additional traits are: a light pale yellowish iris of the eye, contrasting with the black pupil (in Larus cachinnans, the iris of the eye is usually very dark, not contrasting with the pupil, and the eye looks almost black), a deep red orbital ring (in Larus cachinnans, the color of the orbital rings varies from pale orange to red), rich yellow legs (many Larus cachinnans birds have pale yellowish legs during the breeding period, and only some have bright yellow legs), bright yellow bill coloration, with a strong red gonys spot (in Larus cachinnans, the bill is usually less bright, the gonys spot is reddish and relatively small). Th us it can be concluded that L. michahellis occasionally breeds in Odesa at least since 2009, and the nest (fi g. 3) discovered by Rusev et al. (2011) indicates that Odesa is the most northern breeding area of this species in the Black Sea region. In addition to this case of proven breeding of Larus michahellis in Odesa, there is also a reported observation of a mixed pair of L. michahellis and L. cachinnans in a small colony of L. cachinnans located on a pier in waters of the Odesa seaport. Th ere a male L. michahellis copulating with a female L. cachinnans were observed using powerful optics at a distance of more than 0.6 km, on April 1, 2015 (Panchenko et al., 2015). Th e breeding sites of the Yellow-legged Gull in Odesa are located 300 km away along the coast from the nearest breeding sites in Constanta. However, adults of L. michahellis, singles or in groups, were oft en seen on the sea coast between the Danube Delta and Odesa in summer (Yakovlev, 2015; M. V. Yakovlev, personal communication; P. S. Panchenko, personal communication). It is possible that those birds could form pairs, which then bred in Odesa. L. cachinnans is widespread in area north of Constanta along the western coast of the Black Sea. According to R. Klein and A. Buchheim (1997), gulls breeding on islets in coastal lagoons north of Constanta have the L. michahellis phenotype. All gulls breeding in this locality and studied by mitochondrial DNA analysis belonged to this species (Liebers et al., 2004). Analysis of museum specimens of gulls from the northern part of the Danube Delta (fi g. 1, C) confi rms the habitation of L. cachinnans there. To the north of the Danube Delta, L. cachinnans is distributed to the mouth of the Dnipro River and further to the eastern edge of the Karkinitian Bay along the Black Sea coast (fi g. 1, D), where they breed in large colonies on low-lying islands off the northwestern shores of the Crimean Penin- sula (fi g. 4). L. michahellis is widespread on the Black Sea coast of the Crimean Peninsula (Tsvelykh, 2016). Th ere are reports of its settlements on the southern coast of Crimea, on the Tarkhankut Peninsula and on the Kerch Peninsula (fi g. 4). In the Crimean Peninsula, L. michahellis usually breeds on coastal cliff s and on coastal rocky islets. On the southern Fig. 4. Settlements of Larus cachinnans (circles) and Larus michahellis (triangles) in the northern part of the Black Sea. Yellow fi gures — the species was determined by means of the analysis of mitochondrial DNA, red ones — by means of the analysis of museum specimens or photos of alive birds. According to Belik, 2018; Klein, Buchheim, 1997; Kuzikov, 2021; Liebers et al., 2004; Mnatsekanov et al., 1992; Sikorsky, 2016; Siokhin et al., 2000; Til’ba, Filipov, 2016; Tsvelykh, 2016, 2018 and data from this study. 169Distribution of Sibling Species Larus michahellis and Larus cachinnans on the Black Sea Coast coast of Crimea, gulls oft en breed on the rooft ops of multi-storey buildings in villages and towns (Beskaravainy, 2008). It is noteworthy that in Crimea, gulls began to breed on the rooft ops of buildings in the mid-1990s only (Beskaravainy, Kostin, 1998). Th e easternmost settlement of L. michahellis on the Black Sea coast of the Crimea is Opuk mount in the south of the Kerch Peninsula (Sikorsky, 2016; Tsvelykh, 2016); it has existed here for at least a hundred years (Tsvelykh, 2018). Further to the east, L. cachinnans is widespread on the Caucasian coast of the Black Sea (fi g. 4). Th ere, large populations of these gulls were found near the southeastern edge of the Taman Peninsula in the vicinity of Anapa city and, to the north of it, on the Kiziltash estuaries (Mnatsekanov et al., 1992). Further south along the Black Sea coast of the Caucasus, gull populations are absent up to Novorossiysk, where L. michahellis breeds on the rooft ops of buildings, having settled along the eastern coast of the Black Sea from the southern side (see above). Th e coast of the Sea of Azov connected by a narrow strait with the northeastern part of the Black Sea, is abundantly populated by L. cachinnans. Along the coast there are nu- merous settlements of that species (fi g. 4), on low-lying islands and on sand spits. On the coast of the Sea of Azov, one small settlement of L. michahellis is known: the birds breed on coastal rocks near Cape Kazantip, in the north of the Kerch Peninsula. Interestingly, a large breeding colony of Larus cachinnans is located less than 10 km south of this settlement, on the low-lying islands of the saltwater Aktash Lake. Th ere, the settlements of the studied sibling species are as close as possible (fi g. 4), which may create for them preconditions for limited hybridization (Tsvelykh, 2016). Th e data obtained make it possible to outline the current ranges of L. cachinnans and L. michahellis on the Black Sea coast. Larus michahellis is spread along the entire southern coast of the Black Sea; along the eastern coast, it is distributed northward to Novorossiysk, and along the western coast to Constanta (fi g. 5). In the northern part of the Black Sea, this species is widespread on the sea coast of the Crimean Peninsula and breeds in isolation in Odesa. Larus cachinnans occurs mainly in the northwestern part of the Black Sea from the Constanta northward to the Karkinitian Bay (fi g. 5). In the northeastern part of the Black Sea, that species is spread only at the southeastern edge of the Taman Peninsula southward to Anapa. Larus cachinnans is widespread along the coast of the Sea of Azov (fi g. 5). I am very grateful to I. T. Rusev for the very valuable photographs provided for this study and to P. S. Panchenko, M. V. Yakovlev and N. S. Atamas for providing me with important information. Fig. 5. Breeding ranges of Larus michahellis (orange) and Larus cachinnans (red) on the Black sea and Sea of Azov coasts. 170 A. N. Tsvelykh References Belik, V. P. 2013. Recent transformation of avifauna of Northwest Caucasus and its causes. 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