Identification of American Herring Gull in a western European context

Identification of American Herring Gull in a western European context12 1314 1512-15 Presumed American Herring Gull / Amerikaanse Zilvermeeuw Larus smithsonianus, juvenile, Cobh, Cork, Ireland,8 January 2001 (Jim Wilson). Underparts streaked, not as uniform as underparts of two first-winter smithsonianus present atsame time. Confusingly similar to some ‘dark’ juvenile argentatus-types, but upper- and undertail-coverts densely barred darkand tail almost entirely dark (see plate 9), strongly indicative of smithsonianus.Juveniles (plate 1-23)There is wide variation in the appearance ofjuvenile smithsonianus, from the most distinctivetype (c 60%) which is very dark and practicallyuniformly textured on the underparts (plate 1), toless striking birds which have more mottled, oreven pale-streaked, underparts and which couldeasily escape detection among a flock of largegulls in Europe (plate 5). In addition to this variationwhich can be seen in Atlantic coast populationsat, for instance, Cape May, New Jersey, inSeptember, there appears to be another ‘type’ ofsmithsonianus which deserves particular attention.Unfortunately, we have virtually no firsthandexperience with what Howell et al (1999)referred to as ‘Pacific coast [American] HerringGulls’ which are presumed to originate fromhigh-latitude populations and apparently performa long-distance migration to winter mostly inCalifornia. Judging from a few published photographs(eg figures 1, 6 and 10 in Howell 2001)and some of the American Herring Gull videoclipsfeatured in The large gulls of North America(Dunn et al 1997), the birds that winter in westNorth America include a much higher proportionof what might be described as ‘problematic’ firstyearsthan we observed on the east coast.Possibly the closest thing to a ‘high-latitude’-typesmithsonianus we have seen on this side of theAtlantic is a bird, still in full juvenile plumage, atCobh, Cork, Ireland in January 2001 (plate 8, 9and 12-15, Diggin 2001). It was one of three7