American Herring Gull adult April
The issue of Dutch Birding 26: 151-179, 2004 contained a very comprehensive paper on the identification of adult smithsonianus in a European context, titled: Identification of adult American Herring Gull. It was written by Peter Adriaens & Bruce Mactavish. The outstanding text is copied on this webpage, with links now added to various Canadian and European birds placed on the ORG-website. When appropriate, more details from recent field research has been added as well. Full PDF download: HERE.
Identification of adult American Herring Gull
-Peter Adriaens & Bruce Mactavish-
BACK TO PART 1: INTRODUCTION & GENERAL COMMENTS
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BACK TO PART 3: DETAILED PRIMARY DESCRIPTION P8-P4
THIS PAGE IS PART 4: FINAL COMMENTS
Pontic Gull and hybrids
Since there are some similarities between NF smithsonianus and Pontic Gull in primary pattern and bill pattern in winter, we discuss the latter species here also. In addition, hybridization between Pontic Gull and Eastern Baltic Herring Gull has been recorded in Poland (Faber et al 2001), which may create some more identification problems. Pontic Gull and hybrids are normally slightly darker mantled than NF smithsonianus, they often have a yellowish or greenish tinge on the legs, and they have little or no winter head streaking, except for some fine brown hindneck streaks (rarely, there can be fine pencil-streaks around the eye, but these are less distinct than the hindneck streaks). In Pontic, the iris regularly has some dark pigmentation, the legs are often longer and thinner, in many with longer tibia than in any herring gull, the bill is on average slightly thinner, the primary projection is longer, and the forehead may be more sloping.
The primary pattern of adult Pontic Gull usually differs from that of NF smithsonianus in that the white mirrors are larger, and the black bands on P5-6 are slightly broader and more solid on average (less tendency towards a thin ’W', also because the amount of black is typically larger on the outer than on the inner webs). A ’bayonet”-pattern on either P7 or P8 is also less frequent. In all of the 71 birds examined by Mierauskas & Greimas (1992), the white mirror of P9 always extended onto the outer web. The white mirror on P10 was also very large, with only 26% of the birds showing some black between the mirror and the white primary tip. Likewise, all of the eight putative hybrids from Poland that we examined showed a white mirror on both webs of P9. No birds had a ’bayonet’ on either P7 or P8. The black bands on P5-P6 were also more solid and thicker on average; only one bird had a ’W'-pattern on P6, and while all but one had a complete black band on P5, only two birds showed a distinct ’W’ here. The criteria for separating NF Herring Gulls and European Herring Gulls should also be conclusive for ruling out Pontic Gull and its hybrids.
Glaucous x herring gull hybrids
Hybrids Glaucous x European Herring Gull are known from Iceland and the Kola Peninsula,
Russia. Hybrids Glaucous x American Herring Gull occur in north-eastern Canada. Hybridization is also known from Greenland. While adult hybrids usually show characters of both parent species (eg, greyish to blackish-grey wing-tips, very short primary projection, etc), a few birds at the darkest end can be similar to herring gulls, and may have long, broad tongues on the outer primaries (influence from Glaucous Gull). However, such birds will normally combine these long tongues with large white mirrors on P9-P10 (completely covering both webs on P9), generally reduced dark markings on the outer webs of P6-P8, and little or no dark markings on P5 Ingolfsson 1970, 1993, Sibley 2000, Olsen & Larsson 2003).
Notes on geographical variation (table 9-14)
The following is merely an attempt to give some idea of the regional variation in North America. The samples from the different regions outside Newfoundland were small and only occasionally included breeding birds. Therefore, the descriptions have no taxonomic value; we just hope that they will motivate others to examine smithsonianus in more detail. The results are given in table 9-14. In short, it seems that the primary pattern on the East Coast of the USA is quite variable but perhaps somewhat intermediate between that of NF smithsonianus and those populations more to the west. It is difficult to interpret data from outside the breeding season, since they may include some Newfoundland birds Indeed, NF Herring Gulls ringed on breeding colonies near St lohn’s, Newfoundland, have been recorded - mostly in winter - in Virginia, New Jersey, New York and Maine. Olsen & Larsson (2003) mention that 20-30% of adult smithsonianus from Massachusetts to Virginia did not have a white mirror on P9, as opposed to less than 15% of Newfoundland birds (11% in our sample). They also state that black markings on P4 occur in 25% of East Coast birds (but only 7% in Massachusetts) – as opposed to only 2% in NF smithsonianus (3.5% in our sample).
The inland Ontario (or Niagara) population was mostly studied in winter, so its origins are not entirely clear. In any case, the smithsonianus occurring in that region in winter have more black in the wing-tips than Newfoundland birds, showing shorter grey tongues to P8-P10, often no white mirror on P9 (in 90% of those examined; Jonsson & Mactavish 2001), usually a complete black band on P5, and some black on P4 in quite a few birds (34%). All birds had an uninterrupted black band between the white mirror and tip of Pl0. In addition, the pointed black wedges or black ’bayonets’ (when present) on P7-P8 can be really long, eg, almost reaching the primary coverts on P8. Likewise, the pointed wedge on the outer web of P6 can be longer than in NF smithsonianus. There is not much white on the tongue-tips of P5-P8. According to Jonsson & Mactavish (200l), the winter Niagara birds appeared smaller, with shorter legs, less sturdy bills, and more rounded heads than Newfoundland birds. Many looked quite petite, similar in fact to several of the Kumlien’s Gulls L glaucoides kumlieni that were present.
West Coast and western Canadian populations are similar to the winter Ontario birds but seem to have even shorter grey tongues on P8-Pl0. In addition, some birds have a lot of black on the outer web of P8; the outer web can be all-black almost up to the primary coverts. White on the tongue-tips of P5-P8 is very restricted, and is regularly absent on at least P8. On P10, there is typically a broad, black subterminal bar between the mirror and the white tip - on average far more distinct and broader than on Newfoundland birds. Olsen & Larsson (2003) recorded 64% of birds at Lake Superior without a mirror on P9, and 75-80% in California/northern Mexico. In addition, they found that 50% of West Coast adults had black markings on P4, and a few even had a little black on P3, When BM was studying breeding smithsonianus in the field in Yukon, he had the impression that their upperparts were slightly darker than in Newfoundland birds, and that their eyes more often had a darker, somewhat olive-yellow iris, frequently with dark specks, resulting in very dark eyes.
As a side note, we would like to highlight that our sample from Alberta contained three birds
(skins) with a large white mirror on P9, covering both webs, which seems surprising for western birds. All three were from the Athabasca region. Birds in our sample from Alaska appeared more variable than birds of other western populations.
We would like to thank the following people for providing us with photographs: Peter Alfrey,
Richard Banks (Smithsonian National Museum of Natural History), Andreas Buchheim, Lieven Caekebeke, Nils van Duivendijk, Krista Fahy (Santa Barbara Museum of Natural History), Kimball Garrett (Natural History Museum of Los Angeles County), Steve Howell, Andrew Kratter (Florida Museum of Natural History), Grzegorz Neubauer, Rudy Offereins, Robin Panza (Carnegie Museum of Natural History), Dennis Paulson (Slater Museum of Natural History), Laurent Raty, Visa Rauste, Geert Spanoghe, Peter Stewart, Paul Sweet (American Museum of Natural History), Steven Vantieghem, Rik Winters, Chris Wood (Burke Museum of Natural History) and Kristof Zyskowski (Peabody Museum of Natural
History). We also wish to thank Gunter De Smet and Phill Holder for providing us with literature.
Gunter De Smet also arranged access to the Royal Belgian Institute of Natural Sciences, We had lengthy but fruitful discussions with a number of people, and would like to mention in particular Ted Hoogendoorn, Bert-Jan Luijendijk, Visa Rauste and Rik Winters. The text benefited from comments by Klaus Malling Olsen. Finally, we thank the Dutch Birding Association for financially supporting the project through the Dutch Birding Fund (cf Dutch Birding 24: 125, 2002).
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East Coast birds