Black-tailed Gull

The long-awaited and highly recommended “Gulls of Europe, Asia and North America” by Klaus Malling Olsen and Hans Larsson (Published by Helm, 2003) is a superb and detailed work, helping to advance gull identification significantly. It provides detailed information on molts and primary patterns, supported by clear and accurate drawings and series of extremely useful photographs.

The book, though, had major flaws that went uncorrected in the editorial stages (with contradictory and repetitive statements on distribution, mislabeled photographs and inaccurately colored maps), and has now been recalled to the publishers, providing the authors, it is believed, with a further chance to amend some other basic errors in this otherwise excellent work. This note therefore aims to provide some timely basic information on the status and distribution of 22 gull taxa recorded in South Korea, with some additional notes from DPRK/North Korea, based largely on personal observations, on information received by Birds Korea, and on the Status code given in Lee, Koo & Park's “A Field Guide To the Birds Of Korea” (published by LG in 2000), and from information provided by Tomek (1999) and other researchers about gulls in DPRK.

It is written specifically (and broadly) to help improve the distribution and migration sections given in Malling Olson and Larsson (2003), where such sections relate to South Korea, and as a supplement to our online paper on the Herring Gull Assemblage.

Accounts

The broad Status and distribution of each of the 22 gull taxa recorded in South Korea up to and including February 2004 is given. Each account includes the status given by Lee, Koo and Park (2000), further developed based on personal observations and more recent information, in several cases supplemented by information from DPRK. The following distribution section remains intentionally broad, referring frequently to the east coast (rocky, with small beaches, numerous harbors, and deep sea inshore waters, and the long Guryongpo peninsula), to the south coast (wider bays, with extensive tidal-flats, e.g. at the Nakdong estuary and Suncheon bay, and numerous rocky islands, including the volcanic Jeju island in the far southwest) and the west coast (extensive estuaries and tidal-flats formed by the major rivers, now dammed or otherwise, of e.g. the Han, the Geum, Saemangeum and the Yeongsan rivers that flow into the Yellow Sea).

The accounts should further be considered with the following understanding:

1. In spite of a recent and rapid increase in interest in gulls and gulling, knowledge of gulls is still rather limited in South Korea, and in neighboring North Korea, Eastern China, the Russian Maritimes and Japan (“Far Eastern Asia”), and there has not been a growth of expertise on gulls within the region comparable to that experienced in e.g. Europe and the United States.

2. There have been very few gull breeding studies within the region, or adjacent regions, with banding programs largely limited to obvious species such as Black-tailed, Relict and Saunders’s Gull, and to a much lesser extent Mongolian Gull. There has been no significant research known to Birds Korea conducted in the breeding grounds of several of the major forms occurring, potentially or otherwise, within South Korea (and neighboring countries), including Vega Gull, Kamchatka Gull and on the widespread form taimyrensis. This considerably undermines confidence that can be attached to descriptions of both plumage minutiae and of distribution given in recent gull papers and publications, including Malling Olsen and Larsson (2003).
   Can gullers really be confident that Kamchatka Gull is “A distinct [the largest] taxon, probably requiring fully specific Status”, without knowing at all clearly the biometrics and plumage details of eastern heinei and the full range shown by Kamchatka Gull itself?

   Can we even know that taimyrensis is a hybrid form, until we have at least some evidence directly from the breeding grounds of extensive hybridization - something apparently refuted by Yesou [2002])?

Black-tailed Gull Larus crassirostris

Status given in Lee, Koo & Park (2000): Abundant resident.

Status

A numerous and widespread coastal and marine species found in South Korea throughout the year, with seasonal movements and some mid-winter influx from northern areas. Interestingly, an influx was noted inland in Pyongyang, DPRK, between July and November 2000, suggesting overland migration - while Tomek (1999) notes the species as a migrant and breeding species in DPRK (with flocks "numbering from several tens to several hundred individuals in the breeding season" and of "several thousand birds" in the migration season).

Distribution

Breeds in several colonies on rocky offshore islands along all three coasts (many small colonies in northwest). Many juveniles disperse July-August onward to coastal areas, after which it becomes numerous in harbors and on rocky islands on the east coast and to a lesser extent the south coast, in addition to western tidal-flats. Many birds from northwestern colonies in Yellow Sea perhaps disperse southward in the mid-winter period, but still ca 300 seen at sea in mid-Dec 2003 close to 38 D N (pers. obs.), with flocks also concentrated at favored sites along the west coast (e.g. at Incheon, Geum River and Baeksu tidal-flat in the southwest, where ca 3940 present on January 4, 1999: pers. obs.). Birds wing-tagged at breeding islands of Rebun and Rishiri (northern Japan) have been found at several localities along the South Korean east coast in at least the mid-winter period (January-March 2003, and again in December 2003) [Go to: Information on Flagging of Black-tailed Gulls in Japan].

The map of both the breeding and wintering distribution in Malling Olsen and Larsson (2003) is therefore inaccurate - breeding sites on the coasts of Korea need to be added to the map, while the Yellow Sea (at least the South Korean part of it) and the East Sea should also be included as an important wintering area for the species.

Common Gull Larus canus, subspecies heinei and kamtschatschensis

Status given in Lee, Koo & Park (2000). Common winter visitor.

Status

Locally numerous winter visitor, almost exclusively coastal in South Korea, though "dozens" regularly over-winter inland in Pyongyang, DPRK (ca 50 km from coast). Kamtschatschensis suspected as being rather more numerous than heinei. However, L. canus is considered extremely variable in size and appearance in South Korea (e.g. Moores & Moores, 2002a), and many birds possibly cannot be safely ascribed to subspecies on present knowledge. Lack of knowledge of forms, possibility of intergrades and lack of banded birds of known origin should perhaps prevent overstatement of distinctiveness of Kamchatka Gull, for the present at least.

Distribution

Found especially on beaches and harbors along the east coast, and to a lesser extent on other coasts, where first birds typically arrive in October. Present in several favored localities (e.g. Guryongpo, Nakdong, Incheon) in significant concentrations - rarely up to several hundred individuals at peak (reached in mid-winter period). Return passage in March; few birds remaining into April and more rarely into May.

Ring-billed Gull Larus delawarensis. Not listed in Lee, Koo & Park

One presumed second winter seen at Suncheon bay on May 3rd 1997 (NM).

Glaucous-winged Gull Larus glaucescens

Status given in Lee, Koo & Park (2000): Rare winter visitor.

Status

A scarce winter visitor, at the southern limit of its regular wintering range.

Distribution

An exclusively coastal gull recorded most frequently between November and March along the east coast (probably 10-50 present most winters), especially from the Guryongpo peninsula northwards. Much less regular along the south coast (e.g. at the Nakdong estuary, where only 3 personal observations between 2002-2003), and very few records on the west coast. Most individuals are First-winters.

The Map in Malling Olsen and Larsson (2003) shows the limit of winter range in East Asia a little inaccurately: the winter limit should perhaps be extended to encompass Chiba Prefecture in Japan and the east coast of South Korea.

Glaucous Gull Larus hyperboreus

Status given in Lee, Koo & Park (2000): Scarce winter visitor

Status

A fairly scarce winter visitor to South Korea, though rather more numerous than L. glaucescens. Most are considered to be of the subspecies pallidissimus, with occasional small individuals possibly belonging to barrovianus.

Distribution

An exclusively coastal and marine gull, which typically arrives in late October, with most departed by March. This species is most numerous along the east coast (very occasionally in small groups of 3-5), with odd individuals appearing regularly at most other key gull sites (such as the Nakdong on the south coast and the Geum estuary on the west coast).

The map in Malling Olsen and Larsson (2003) shows the limit of the regular winter range in East Asia inaccurately. The regular winter limit should best be extended to cover the east coast of South Korea. In addition, it is described by Fiebig (1993) as a rare but regular winter visitor to the east and west coasts of DPRK.

Iceland Gull Larus glaucoides

Status given in Lee, Koo & Park (2000): Vagrant.

Status

There are several “good” recent claims of Iceland Gull in winter, following the first record of one at Goseong, NE coast, in December 1997 (Park & Yi, 1999).

Distribution

Several claims of individuals in winter (December-March) on the east coast of South Korea, with the most recent records involving a winter adult moving into breeding plumage (photographed by Kim Hyun-tae, Kim Ju-Heon and Kwak Ho-Kyeong on the east coast between January 18 and 22, 2003), and a first winter seen well in flight on March 8 (NM). All records are believed to belong to “nominate” glauciodes. (Note, however, that Malling Olsen and Larsson [2003] state that "an unidentified taxon might occur in N Russia" [p.215]. Considering the comparatively high prevalence of birds showing bill proportions or primary projections better fitting glaucoides, as well as perhaps some elements of hyperboreus, might this unidentified taxon possibly be the more likely origin of many of the claims of Far East Asian Iceland Gulls? )

Malling Olsen and Larsson (2003) mistakenly do not include South Korea as a country where the taxon has been recorded as a vagrant.

Thayer's Gull Larus thayeri

Not listed in Lee, Koo & Park (2000).

There are several recent claimed records of adults in mid-winter (December-February), including 2 adults at Uljin on February 27th, 1999, and one on the Han River in Seoul, in February 2000 (Lee Ki-Sup in lit.); as well as one photographed Second-Winter on January 29th 2001 (Park Jin-Young in lit.). More recent claims with supporting photographs include an apparently ’classic’ Juvenile-First winter at Sokcho on December 1st, 2002 (Choi Tae-Hon), a First-Winter at Jumunjin (Park Jin-Young in lit.), an adult on February 23, 2003 (J. King and G. Carey in lit.), and an adult at Gangneung on March 23 (Choi Soon-Kyoo).

This taxon is not yet listed for South Korea by Malling Olsen and Larsson (2003).

American Herring Gull Larus smithsonianus

Not listed in Lee, Koo & Park (2000).

There are several recent claimed records (first from about 2000, with an adult at Uljin in January 2001 and February 2002: Lee Ki-Sup in lit.) especially on the east coast of South Korea, many of which are supported by photographs. In 2003 claims included an adult between January 18-22 (Kim Hyun-tae, Kim Ju-Heon and Kwak Ho-Kyong), and another adult on February 26, 2003 [J. King and G. Carey, in lit.]) both on the east coast. In addition, individuals photographed by Choi Soon-Kyoo and labelled as Vega Gull on January 12th and February 14th, both on the northeast coast, appear to NM to show many features of Juvenile-First Winter and Second Winter smithsonianus. A juvenile presumed-smithsonianus was also seen (but not photographed) at Guryongpo on December 8, 2003 (NM).

This taxon is not yet listed for South Korea by Malling Olsen and Larsson (2003).

Caspian Gull Larus cachinnans subsp: mongolicus

Listed in Lee, Koo and Park as Yellow-legged Gull Larus cachinnans, an uncommon winter visitor.

Status

A widespread and locally common taxon, most especially from November-March, though with small numbers present at several sites through the summer, and breeding reported on several offshore islands in the northwest of the country. This is also most likely the taxon reported as nesting in three provinces of the DPRK (first citation given by Tomek, 1999, dating back to 1964).

Distribution

The first small flocks typically form in August (at e.g. Ganghwa, Seosan and the Geum estuary), and build up through the autumn along beaches and in estuaries (and occasionally out to sea). This, however, is the gull found most abundantly in winter on freshwater habitats - especially large rivers, occurring up to 50 km or more from the coast on e.g. the Han and the Geum rivers. On freshwater sections of the Han River especially, 1 000+ are regularly recorded in February and March. The Mongolian Gull seems to be rather more variable in structure and plumage than suggested by Malling Olsen and Larsson [2003] (Go to: A consideration of "The Herring Gull Assemblage" in South Korea), with possibly several apparently distinctive types noted in South Korea.

In addition, the mapped range is significantly inaccurate. Mongolicus is generally considered a rather scarce winter visitor to e.g. Hong Kong (which is included in the wintering range mapped by Malling Olsen and Larsson [2003]), while it is not mapped in South Korea at all: a country with perhaps the largest known wintering concentrations.

Caspian Gull Larus cachinnans subspecies barabensis: Steppe Gull

Not listed in Lee, Koo & Park (2000).

Although identification criteria remain poorly known, there have been one of two recent claims of probable Steppe Gull in South Korea, including one possible summer adult in October 2002 (photographed by van Den Berg and Robb, considered possible barabensis by NM), and two winter adults (NM, March 2003): all were on the east coast.

Vega Gull Larus vegae including subspecies vegae and birulai

Listed in Lee, Koo & Park as Herring Gull; status given as common winter visitor.

Status

This is a widespread and numerous species in winter. Due in part to possible confusion between summer plumaged adult Vega and Mongolian Gull, the taxon is rarely recorded, if at all, in summer in South Korea.

Distribution

Vega Gull is widespread and fairly numerous at all of the main coastal gull sites. Main arrivals take place in late October and through November, with concentrations of several hundreds at key sites, including the Guryongpo peninsula and the main harbor on Jeju island, through until March. Numbers appear to decline in late March, with only small numbers remaining into April and May. It is seldom recorded far inland, being greatly outnumbered by Mongolian Gull on the Han River in Seoul for example.

The map in Malling Olsen and Larsson (2003) appears to suggest mistakenly that Vega Gull is widespread both coastally and inland in Japan and South Korea. In addition, their discussion on “hybrids” appears to be presently clouded by lack of direct evidence of hybridization, cf. Yesou (2002). Many birds with yellow leg tones and reduced head streaking when compared with vegae in Korea (representing very approximately 1 in 30-100 large gulls on the east coast) could therefore well refer to birulai rather than to suspected hybrids between vegae and heuglini.

Slaty-backed Gull Larus schistisagus

Status given in Lee, Koo & Park (2000): Common Winter Visitor

Status

Locally common winter visitor, with very occasional birds oversummering (e.g. in the Geum estuary in 2003).

Distribution

The Slaty-backed Gull is an exclusively coastal and marine gull, favoring rocky islands and coasts with harbors. As such in winter (October-March) it is relatively numerous along the east coast, though seldom in concentrations of more than 10-30 birds per harbor, occurring with increasing scarcity along the south and west coasts. High counts on the east coast include 250 at Mopo harbour and 150 at Samjung (both Kyeongsangbuk Province) in January 2001 (Martin Sutherland in lit.).

It occurs in mid-winter in very small numbers in the Yellow Sea on e.g. Baekryong and Socheong islands, at nearly 38 D N, as well as at Song Do tidal-flat (usually 2-3 present) in Incheon, and e.g. in the southwestern Daeheuksan islands. There is at least one record of a Japanese-ringed Slaty-backed Gull in Korea.

Heuglin's Gull Larus heuglini, Subspecies heuglini and taimyrensis

Status given in Lee, Koo & Park (2000): Uncommon winter visitor.

Status

The Status of both nominate heuglini and especially of taimyrensis, the latter considered variously to be a hybrid population between Vega and nominate Heuglin's Gull (e.g. Malling Olsen and Larsson, 2003) or an eastern subspecies of Heuglin's Gull , remains highly confused. The Status of taimyrensis becomes even more complicated by lack of knowledge surrounding the possible degree of variability in Vega Gull and even the existence or otherwise of birulai. For an assessment of this taxonomic puzzle, please go to: A consideration of "The Herring Gull Assemblage" in South Korea, and also to Yesou's (2002) “Trends in systematics”, published in Dutch Birding 24: 271-198.

Distribution

Birds considered to be taimyrensis occur in South Korea in largest numbers during migration, with the first individuals appearing on both the west and east coasts in late September, followed by a peak in numbers in October into early November. At such times “pure” concentrations of up to 30 individuals (both adults and juveniles) have been recorded. Later in the mid-winter period, the taxon is widespread in small numbers (typically less than 10 per 100 Vegae) on all coasts, preferring rocky harbors (e.g. on Jeju), and often feeding around fishing boats. It appears to be extremely scarce on freshwater. In February and March numbers appear to increase again (though less obviously than during southward migration), with small numbers still present, especially on the east coast, until April or even May.

The timing of peak numbers during migration accords well with their being described as the commonest large gull wintering in Hong Kong by Malling Olsen and Larsson (2003). Puzzlingly, however, their map for taimyrensis excludes both Hong Kong and the south China coast.

Pallas's Gull Larus ichthyaetus

Not listed in Lee, Koo & Park (2000), this species has now been recorded (and photographed) at least three times in South Korea (Go to: Rarity Reports):

1. Second-winter, Han River in Seoul, December 1-4, 2002 (Tim Allison)

2. First-winter into First-summer, Nakdong estuary, Busan, March 17-19, 2003 (NM)

3. First winter, at sea near Eocheong Island, Gunsan City, March 25, 2003 (NM)

4. Adult, Han River in Seoul, February 7, 2004 (Kim Dae-Hwan)

Puzzlingly, Malling Olsen and Larsson (2003) list “Korea” as a country where the species has been recorded as a vagrant, though all references cited predate the first record.

Black-headed Gull Larus ridibindus

Status given in Lee, Koo & Park (2000): Common Winter Visitor

Status

The Black-headed Gull (subspecies sibiricus, with no proven records yet of nominate) is a locally abundant migrant and winter visitor, occurring at a few key sites in concentrations of several thousands.

Distribution

Occurs in small numbers inland on migration and in winter (with 10-15 birds wintering at Joonam reservoirs in the southeast for example), but like all other gull species in South Korea - with the exception of Mongolian Gull - this species is largely coastal. Typically arrives in very small numbers in August/September, with main arrivals along the east coast probably in November (e.g. with 5000+ recorded feeding offshore at Guryongpo on Nov 22nd, 2002: pers. obs.). Numerous along the east coast in the mid-winter, with further significant concentrations at larger estuaries along the south and west coasts, though comparatively scarce in the far northwest in January. Northward movements increasingly apparent from February, with small flocks occurring inland on rivers through March. Most have departed by mid-April, with only small numbers attempting over-summering (most especially in the Geum estuary, where e.g. 17 were still present on June 13, 2003: Pers. obs).

Slender-billed Gull Larus genei

Not listed in Lee, Koo & Park (2000), and not listed yet for South Korea by Malling Olsen and Larsson (2003), this species has been recorded once in South Korea: a winter adult was found and photographed in Gwangyang Bay, south coast, at least between January 9th -11th, 2002 (NM and Kim Su-Kyung, Go to: Slender-billed Gull: 09 January 2002: Gwangyang Bay).

Saunders’s Gull Larus saundersi

Status given in Lee, Koo & Park (2000): Uncommon winter visitor and scarce resident.

Status

Surveys in 1999, 2001 and 2002 located ca 2500- 3000 Saunders’s Gulls in South Korea in mid-winter (pers. data), while small opportunistic colonies have been located at least three times, the first in 1998 (Moores, 1998), which was occupied by about 120-130 adults. Tomek (1999) also cites several records of breeding plumaged adults in DPRK during the breeding season, adding that nesting in the DPRK remains "only a hypothesis".

Distribution

Nesting in salt-marsh in areas undergoing reclamation (Shihwa, 1998; Yeongjeong ca 1999-2001; Song Do ca 2000-2003), Saunders’s Gulls are effectively confined to the mud-sand or muddy substrate inner part of estuaries in South Korea in winter, being most numerous at key west coast sites in November-December, and on the south coast in mid-winter. They are rather scarce in the southwest, where sandflats predominate, and on the largely rocky and sandy east coast. Key sites include (from north to south) Song Do (Incheon, with over 600 at peak in 2002); Namyang Bay; Asan Bay; Cheonsu Bay; the Geum estuary; and Saemangeum on the west coast; and on the south coast, (west to east) Posong Bay, Suncheon Bay and Gwayngyang Bay, Namhae Island and the Nakdong estuary. The largest claimed day count is 2 000 at Suncheon (Park Jin-Young pers. com). Numbers fall away in February and March, with some evidence of northward migration through e.g. the Nakdong estuary and along the east coast.

Relict Gull Larus relictus

Status given in Lee, Koo & Park (2000): Rare winter visitor

Status

The Relict Gull is a scarce to rare winter visitor to South Korea, much more numerous in cold winters than mild ones.

Distribution

The Relict Gull is strongly associated with sandy substrates - either open beaches or more typically the sandy outer parts of estuaries. The species typically arrives in late November or early December (when several appear on beaches along the east coast, at e.g. Chumunjin and Pohang), with peak counts recorded in February, rapidly falling away again in March. There are a very few records from later in spring, with for example a full-summer plumaged adult photographed at Gangneung, April 14th 2002 (Choi Soon-Kyoo), and one first winter in the Geum estuary in late April 2003 (Tim Allison).

Known regular wintering sites for the species in South Korea include Song Do (Incheon), where a peak count of 143 was made on February 3, 2001 (NM and CM, 2002), with 14 there on February 14, 2003, Suncheon Bay (where up to 14 noted: pers. obs.), and the Nakdong estuary. The latter site held 65 in January 1991, while more recent counts have not exceeded 26 (in 2000) [online Asian Red Data Book], with between 5 and 15 most winters (pers. obs).

The exceptional numbers of birds recorded in the extremely cold winter of 2001, including large numbers of adults at Song Do and First-winters at several southern and southwestern sites, their behavior, and the very high counts of birds previously recorded in the northern part of the Yellow Sea (between September and November at least), strongly suggest that large numbers of Relict Gull are wintering north of South Korea in coastal areas - i.e. in the northern part of the Yellow Sea, where extensive suitable habitat exists (e.g. Moores & Moores, 2002). This hypothesis has recently been confirmed by exceptional winter counts on the Chinese Yellow Sea coast including 1,645 Relict Gull in March 2003 at Tianjin Paleocoastal and Wetlands National Nature Reserve (Liu Yang et al, 2003), and 3,362 along a 6-km stretch of inter-tidal flats in Tianjin municipality, Gulf of Bohai (northern Yellow Sea) on January 3rd, 2004 (Paul Holt in lit.).

The comments on distribution in Malling Olsen and Larsson (2003) are especially confused in relation to Korea, while the map appears to be based on extremely limited information, omitting the majority of its known non-breeding range.

Sabine's Gull Larus sabini

Status given in Lee, Koo & Park (2000): Vagrant

No details known to Birds Korea and apparently no recent records.

Ivory Gull Pagophila eburnea

Status given in Lee, Koo & Park (2000) as vagrant, based on one record, from Ulleung Island, East Sea, in late autumn, reported by Park & Yi (1999).

Ross's Gull Rhodostethia rosea

Status given in Lee, Koo & Park (2000): Vagrant.

One reported near Busan in mid-winter, reported by Lee and Woo (2000).

Black-legged Kittiwake Rissa tridactyla

Status given in Lee, Koo & Park (2000): Uncommon winter visitor.

Status

The Black-legged Kittiwake, subspecies pollicaris, is a locally common winter visitor (most numerous between October and March), especially along the east coast.

Distribution

Highest numbers are apparently recorded in strong onshore winds, and most especially in late autumn (with e.g. 92 south past Guryongpo in one hour, November 23 2002). It is regular in the seas between Korea and Japan, reaching the southwest approaches and Daeheuksan islands; while it also occurs further north in the South Korean part of the Yellow Sea. Although recorded in small numbers between Gunsan and Eocheong Island, the largest counts recorded in the West Sea appear to be rather further north, with e.g. 334 recorded on October 12, 2003 off Socheong island (Mathias Ritschard et al, pers obs) at almost 38 Degrees North, 600 there in late October, and only 8 observed at sea between Socheong and Incheon during November, suggesting that the October birds were perhaps part of a significant passage of birds, perhaps moving overland (over the DPRK), down into more southern parts of the Yellow Sea. This hypothesis is somewhat supported by the report of a single adult apparently seen ca 50km inland in Pyongyang, DPRK, on October 10th, 2002.

Malling Olsen and Larsson (2003) erroneously give the Status of Black-legged Kittiwake in South Korea as a vagrant, with Korea lying just outside of the southern wintering limit line.

References:

• Fiebig, J. (1993). Dreijahrige ornithologische studien in Nordkorea. I. Allgemeiner Teil und Non-Passeriformes. Mitt. Zool. Mus. Berl. 69 Suppl.: Ann. Orn., 19: 43-99.
• Lee, J-N & Y-T Woo. Ross's Gull Rhodostethia rosea: a new record for Korea. 2000 Annual meeting of Ornithological Society of Korea.
• Lee, W., Koo, T. & J-Y Park.(2000). A Field Guide To the Birds of South Korea. Evergreen Foundation.
• Liu Y., Zhang Z-W, Zhang Y. & H-C Su. (2003). Record congregation of Relict Gull Larus relictus during the migration season. OBC Bulletin Number 38, December 2003.
• Moores C. & N. Moores.(2002). Birds of South Korea. Video. Charlie Moores Video Productions.
• Moores N. (1998). Saunders’s Gull colony in South Korea; first nesting record outside of Peoples’ Republic of China. Oriental Bird Club Bulletin 29, November 1998
• Moores, N. & C. Moores (2002), Wetlands: Korea’s most threatened habitat. Oriental Bird Club Bulletin 36, pp. 54-60.
• Olsen, K.M & H. Larsson (2003). Gulls of Europe, Asia and North America. Published by Helm.
• Park, J-Y & J-Y Yi (1999). First records of the Ivory, Iceland and Yellow-legged Gull in Korea. Bull.Kor. Inst. Orni. 7:59-60.
• Tomek, T. (1999). The birds of North Korea. Non-Passeriformes. Acta zool. Cracov. 42 (1): 1-217.
• Yesou, P. (2002) Trends in systematics. Dutch Birding 24: 271-198.