Materials and Methods

Appendix, pp. 1–11 ДВ Орн. Журнал, 2014. №4. С.3—19 Far East. J. Orn. 4: 3—19 (2014) PUBLISHER’S TRANSLATION INTO ENGLISH Shibaev Yu.V. (2014) Expansion of “Mongolian gull” Larus (Smithsonianus) mongolicus Sushkin, 1925 to the eastern periphery of the Asian Continent // Far East. J.Orn. 4: 3—19. SUMMARY This paper describes the process of colonization of a small island (Furugelm Island) in Peter the Great Bay (Russian side of the Sea of Japan) by a gull species from the Larus argentatus superspecies complex, starting from a single nesting pair in 2004 to a stable population of 72 pairs in 2012. The taxonomic status of the colonist species remains debatable and is not the purpose of this paper. Rather, this is an analysis of the dynamics of regional colonization, characteristics of seasonal migration, and species biology that allow for the conclusion that these observations amount to a sequential colonization by Larus (smithsonianus) mongolicus of the eastern periphery of the Asian continent. The settlers colonized two habitat types from Lake Khanka to the lower reaches of the Amur River: large, freshwater lakes, and coastal islands. The birds that settled on Furugelm Island started as a group of seven differently-aged birds: two mature birds (that bred) and five younger birds of varying maturity. Successful colonization by this species was based on a series of factors, including the protected status of Furugelm Island where the birds fortuitously chose to nest, an abundance of available habitat and food resources, and a relatively low abundance of Slaty-backed gulls, which occupy the same niche. The referred figures and tables are in the original article in Russian, at pages 3—19 This manuscript was prompted by the discovery sites on Furugelm Island in the Far Eastern State of a new nesting species in the Peter the Great Bay Marine Biosphere Reserve and also in spring and (in extreme southwestern Primorskii Krai, Russia); a autumn 2009 during a series of surveys (to search for gull from the Larus argentatus superspecies complex. other concentrations of these gulls) along the entire Following a review of the literature it became clear coastline of Peter the Great Bay. that this was a species colonizing a vast region - the Observations at breeding colonies to detect eastern periphery of the Asian continent. The purpose breeding birds were conducted from 19 June-25 of this text, which documents the genesis of a new August in 2004, and from 14 May-24 June and 07 breeding group of this gull (apparently the first in August-18 September in 2005. In all subsequent years, the Sea of Japan), is to discuss the timing, means, annual monitoring was conducted at the colony, and consequences of the new breeding population including a census of all gulls nesting there. on Furugelm Island in the Far Eastern State Marine The adjacent Tumen wetland—a complex of Biosphere Reserve. land, sea, and shallow bays—was a potential location for feeding habitat suitable for the colonist. In the pre- MATERIALS AND METHODS breeding period in 2005 (from 16 March-19 April), I Field observations were carried out in conducted a series of surveys there, in which all “large, southwestern Primorskii Krai from 2004-2012. Data White-headed gulls” of the L. argentatus complex were collected primarily at colonial waterbird nesting were recorded. Nearly all locations suitable for resting or feeding use by gulls were examined. The length *E-mail: <[email protected]> of a single route was ~ 130 km. Other surveys were (Received 03.07.2014; Accepted 12.11.2014) conducted 24 July-05 August in 2005, and 09 April-10 May and 28 August- 21 September in 2009. Some © 2014 Shibaev Yu.V. © 2014 Amur-Ussuri Center for Avian Biodiversity islands in Peter the Great Bay were surveyed from 06- © 2014 Inst. of Biol. and Soil Sci. FEB RAS, Vladivostok 16 June, 2012. www. birdland.ru Appendix, p. 1 Yu. V. Shibaev RESULTS AND DISCUSSION Yellow Sea in 1910 or even earlier. Historical Analysis Furugelm Island, Peter the Great Bay. Over the Starting in the second half of the 20th Century past few decades, only two gull species have been and into the 21st, scattered reports of a previously- recorded breeding in this area: Black-tailed gull L. unrecorded gull species from the L. argentatus crassirostris and Slaty-backed gull L. schistisagus. superspecies complex appeared across the vast, Nesting by a third species was first recorded in summer temperate region of extreme eastern Asia. Different 2004, on Furugelm Island. There was a single nesting authorities have referred to this species by different pair that year, and by 2012 this number had risen to names, but it is likely that all describe the same ~130 breeding adults (Figs. 3, 4). species. What follows is a brief summary of each After analyzing the literature, I believe regional report (and see Fig. 1). that, more likely than not, all of these previously- Lake Khanka. The first “herring gulls” recorded published records refer to the same species: L. nesting on the lake were in the 1970s (Glushchenko mongolicus. However, it was not my goal to identify et al., 2011). From then, the breeding population grew the taxonomic status of this colonizing species, and in from a few dozen pairs to 1,873 pairs in the present this manuscript I defer to the classification proposed day (Fig. 2; Glushchenko et al., 2011). These Khanka in the latest (fourth) edition of The Howard and gulls have been called different names, including L. Moore Complete Checklist of the Birds of the World argentatus mongolicus (Yudin and Firsova, 1988); L. (Dickinson and Remsen, 2013), where the Asian form (cachinnans) mongolicus (Yudin and Firsova, 2002); is regarded as a subspecies of the American herring L. cachinnans (Glushchenko et al., 2011), and L. vega gull: L. (smithsonianus) mongolicus. Hereafter, I use mongolicus (Firsova, 2013). the conditional name «Mongolian gull» to refer to Lake Udyl, Lower Amur River basin. The first this bird. nesting L. (cachinnans) mongolicus were recorded on Lake Udyl in June 2003, when 16 adult breeding birds The Likely Source of Colonization were seen there. The birds were identified following Although this has not been specifically taxonomy in Olsen and Larsson (2004). This species emphasized or discussed, most (if not all) authors of was subsequently confirmed as a nesting species in previous publications concerning this species note 2010, when 20 young birds were observed, and again that this gull is distributed inland. The Mongolian in 2011, when four nests were found (Pronkevich gull’s primary breeding range is in fact continental and Oleinikov, 2010; Pronkevich et al., 2011). (Fig. 1), so observations in eastern Russia represent Presumably, the species began nesting at Lake Udyl an expansion towards the eastern periphery of the around the year 2000. Asian continent. What follows are some facts and Yellow Sea. There are multiple reports of a large, considerations to support this statement. white-headed gull nesting on a number of islands off 1. At the start of the 20th Century, the Herring the western coast of the Korean Peninsula, both in gull L. a. mongolicus was a very rare bird in the Altai- North and South Korea. Initially, these birds were Sayanskii ecoregion (Baranov and Melnik, 2009). identified as Herring gulls L. argentatus, then later These authors report that there was an increase in as “Mongolian gulls” L. mongolicus (Chong et al., the number of these birds over the past 50 years, 1996: Moores, 2003, 2008; Chan et al., 2010; Moores, and that their colonization of the central Siberian 2012). According to Moores (2012), the “Mongolian section of the Altai-Sayanskii ecoregion during that gull” is a common breeding species on some islands time was “particularly intensive.” Numerous nesting in the Yellow Sea. A colony of ~100 Herring gulls colonies settlements have appeared in the Tuvinskaya were observed on Dokdo Island (North Korea) in and Minusinskaya Hollows, and it has become an the breeding season in 1995 (Chong et al., 1996), abundant nesting species on water bodies of western and Moores (2012), in interpreting information from Mongolia (Baranov and Melnik, 2009). This species Austin (1948), even suggested that “Mongolian gulls” clearly had means and opportunity for expansion. were a broadly-distributed summer visitor to the 2. The increase in numbers of L. a. mongolicus in its Appendix, p. 2 Expansion of “Mongol gull” Larus (Smithsonianus) mongolicus to the eastern periphery of the Asian Continent primary breeding range largely coincides with the first an advanced stage of colonization. breeding records of the “Herring gull” at Lake Khanka The proposed expansion from Lake Khanka (Glushchenko et al., 2011). It seems that these birds might be the result of a deficit of nesting territories began expanding their range into the eastern sections there. The appearance of nesting Mongolian gulls at of the Asian continent sometime in the second half of Lake Udyl (in 2003 or a little earlier) and on Furugelm the 20th Century. That is, the process of expansion Island (2004) generally coincide with two potentially- continued past that documented in #1 above. related events at Lake Khanka: 3. The breeding areas newly-established by 1. Overpopulation. There was high nesting these gulls are approximately the same latitude as the density and limited availability of flat, sandy islands. primary range of the mongolicus form. It is likely easier By 2003, there were already ~1,500 breeding pairs for birds colonizing from the west to acclimate to the there (Glushchenko et al. 2011). seasonal rhythms of an area than if they were to come 2. Deteriorating conditions for nesting.

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