Heuglin's Gull (L. heuglini / antelius)
Amir Ben Dov (Israel)
Chris Gibbins (Scotland)
Hannu Koskinen (Finland)
Mars Muusse (the Netherlands)
4cy / sub-adult heuglini: June
Characteristics and moult of "Baltic Lesser Black-backed Gull" Larus [fuscus] fuscus
Older immature birds
During the second winter, birds moult a variable number of body feathers and wing-coverts. In 3CY spring, the scapulars are usually similar grey as in adults. The wing-coverts -at least the primary coverts- still show variable degrees of scattered brown feathers, and the centres of the secondaries are darker than in adults. The tail is completely white or has irregularly dark markings, often a “broken tail-band”. Retarded 3CY individuals can be similar to most advanced 2CY birds. The bill is yellow with normally extensive black markings on the tip. The legs are yellow to grayish-pink and the eyes already bright as in adults, but can also be still quite dark.
It is unclear to what extent 4CY bird still show immature characteristics in spring. Tentatively birds which only show limited brown in the coverts and virtually adult-like primaries, should be best considered “subadult“ (or 3/4CY) until we better understand the variability of this age group.
Many “subadult” Siberian Gulls differ from adult in early-autumn by the straw-yellow legs and bill and by dark eyes. The upperpart grey tone on the other hand is mostly identical to that of adults. However, at least two birds in Archangelsk showed paler upperparts.
Calls and behaviour
These points are often taken as criteria for identification in large white-headed gulls, however, the features are not treated into details here, since no significant differences are known to exist between the treated taxa and a more detailed analysis is still pending. Almost all types of calls of most large gulls are very similar, but with appropriate experience they can be distinguished from each other or at least give hints.
It is often possible to distinct Lesser Black-backed Gull calls from those of Herring Gulls; Lesser Black-backed Gulls have deeper, nasal calls, and the long-calls are significantly longer. However, it requires much experience and it is often not possible due to individual variations. Still, there are no consistent differences documented for calls between fuscus and the western Lesser Black-backed Gulls or between fuscus and heuglini. (sound gallery on this site, MM.)
When possible both Baltic Gulls as Siberian Gulls use landfills as a major food resource. (As with fuscus, this may reflect a trend from recent years, at least it contradicts earlier views.) A large proportion of the Baltic Lesser Black-backed Gulls on Finnish landfills is immature or subadult, but also full adult birds occur in large numbers. And in Siberian Gull too, the use of landfills is by no means limited to certain age-classes or seasons.
Both fuscus and heuglini occasionally impress, intimidate and threaten with open wings. They adopt an “albatross-pose”, which has been described to occur commonly in Caspian Gull (Klein & Buchheim 1997, Klein & Gruber, 1997), but the process appears less ritualized. Accordingly, both fuscus and heuglini show this behaviour less frequent and less intense compared to cachinnans.
Hybrids between fuscus and heuglini?
After Filchagov et all (1992, and according to M. Hario, in lit.) no fuscus breed on the Kola Peninsula; in the White Sea it only nests in the Onetzki-Bay and sporadically in the western Kandalaksha-Bay. Heuglini occupies large parts of the White Sea coast and also the interior of the Kola Peninsula. Fuscus has been forced to withdraw to a restricted area along the coast over the last decades, and currently this population is geographically isolated.
Hybrids between argentatus and heuglini?
The opinion that heuglini may hybridize with Herring Gulls was repeated recently by Beaman & Madge (1998). This view, also cited in Glutz von Blotzheim & Bauer (1982) and Cramp & Simmons (1983) goes back to a map, published by Johansen (1960), showing a “mixed breeding area” between Larus argentatus antelius (= heuglini) and L. a. omissus (= argentatus), and a short comment on this by Stegmann (1960). However, it is unclear whether Johansen truly meant hybridization (and if so, on what basis), and actually Stegmann speculated "... that one can hardly doubt about the possibility of numerous crossings between the two forms”. On the other hand, Stegmann wrote already in 1934: “On the western border, where the form antelius [= Heuglini] meets pale-backed argentatus, there are no observations of intermediate birds. Both forms on the borders of their distribution breed close to each other, partially in the same area, without mixing, as like they are different species." Filchagov & Semashko (1987, in Hario 1992) reported sympatric breeding of the forms in the Ondomsk Lake (even on the same islands), with no signs of hybridization observed, and Filchagov (1994) found that “L. f
Many thanks to all who have contributed in one way or another to the development of this work, be it through comments on the draft, discussions about gulls, providing photos and other information, or assistance with field work:
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