American Herring Gull (smithsonianus)

(last update: October 30, 2015)

American Herring Gull 3cy October

The issue of Dutch Birding 26: 1-35, 2004 contained a very comprehensive paper on the identification of smithsonianus, titled: Identification of American Herring Gull in a western European context. It was written by Pat Lonergan & Killian Mullarney. The outstanding text is copied on this webpage, with links now added to various Canadian birds photographed throughout the months. When appropriate, more details from recent field research has been added as well. Full PDF download: HERE.

"we" in the text below refers to the original authors.
Description of juvenile plumage: HERE
Description of 1st winter plumage: HERE
Description of 2nd winter plumage: HERE

If any errors occur in this text, please let me know and mail to marsmuusseatgmaildotcom.

Identification of American Herring Gull in a western European context
- Pat Lonergan & Killian Mullarney -

above: American Herring Gull (smithsonianus) 3rd cycle (4CY), March 10 2012, Rockland Harbor, Maine (Jonathan Mays). below: American Herring Gull (smithsonianus) 2nd cycle (3cy), L52 April 13 2013, Hampton beach, NH. Photo: Jon Woolf. Superficially some resemblance, but lower bird has 2nd generation primaries, while the bird above has 3rd gen primaries, with white mirrror visible on the underside of P10 in the far wing.

Description of 3rd winter plumage

As indicated earlier, the proportion of identifiable birds decreases sharply with increasing age. However, there are characters shown by some (perhaps 40-50%) third-winter smithsonianus that appear to be diagnostic. In practice, telling second-winter from third-winter ’herring gulls’ is not always easy; different parts of the bird, for instance, the tail, body, wing-coverts and bill do not necessarily develop at the same rate, so a bird with an ’advanced’ tail pattern, for its age, might have a ’retarded’ bill pattern. Most third-winters will have a more advanced wing pattern than second-winter birds, and virtually all will have adult-like grey (rather than pale brownish) inner primaries (Martin Elliott pers comm).

American Herring Gull (smithsonianus): left 2nd cycle (2CY) December 14 2012, New Haven Harbor, CT (Keith Mueller); right 3rd cycle (3CY) November 05 2011, Chicago, IL (Amar Ayyash). Second and third cycles may look similar, best clues are the adult-like grey inner primaries in 3rd cycle, while these are grayish brown in 2nd cycle. Also, central primaries P4-P6 look more adult-like in 3rd cycles.

Tertial pattern Many show extensive, sharply defined, solid-black / blackish-brown markings towards the bases of some tertials, usually, the middle and / or outer feathers. Such definite, blackish markings as in the best-marked smithsonianus are seldom, if ever matched by European Herring Gulls; however, many smithsonianus do not have such distinctive markings and those with less well-defined, browner, more vermiculated markings overlap with what is commonly seen in European Herring Gulls.

Sharply demarcated deep black markings in tertials, tail, greater primary coverts or seconadries are a good pointer for smithsonianus. Sub-adult European Herrings may also show markings at these locations, but with diffuse borders and pale brown colour. Of course, many smithsonianus (unknown %) also have faint brown spots, but from a European perspective such birds are hard to ID.
Note black markings in tertials and on tail. Sub-adult European Herrings may also show pale brown markings with diffuse borders at these locations, but in smithsonianus the spots should be truely black and very sharply bordered from the grey feather. left smithsonianus sub-adult, July 25 2012, Vinalhaven, ME (Keith Mueller). right smithsonianus sub-adult, August 04 2012, Maine (Dominic Mitchell).
The secondaries show similar markings: deep black centres, sharply set of from the grey feathers. left smithsonianus sub-adult, August 15 2005, Chesapeake Bay, Virginia (Jim Frazier). right smithsonianus sub-adult, September 03 2013, Stratford, CT (Donna Rae Henault Caporaso).
Again sharply demarcated spots, on the greater primary coverts in these birds. left smithsonianus sub-adult, October 19 2012, Nova Scotia, CA (Peter Brannon). right smithsonianus sub-adult, December 04 2011, Owls Head Harbor, Maine (Jonathan Mays).

Secondary pattern Unlike European Herring Gulls, many smithsonianus of this age and older have well-defined black markings on the secondaries. The extent of this feature varies individually; on some birds, virtually every feather is marked with black while, at the other extreme, the secondaries are entirely adult-like. Many, however, are in-between and show a limited extent of clean black on just a few secondary-feathers but are nevertheless distinctive. In European Herring Gulls of the same age, the secondaries are often irregularly vermiculated brownish; they only rarely show such discrete black markings.

Tail pattern The tail pattern varies from being very extensively black, like many second-winter birds, to being practically all white with just one or two dark smudges or spots. On many, an irregular pattern of rather distinct solid-black spots is somehow eye-catchingly different from patterns usually seen in European birds, and can recall the ’piano-key’ type tail pattern of a well-marked second-winter Ring-billed Gull L delawarensis. While a few third-winter-type European Herring Gulls may show similar markings, most have less clear-cut, and more diffuse or vermiculated rectrix-markings.

Bill colour Similar to European Herring Gulls of the same age (pinkish/pale straw with a broad dark gonydeal band) but quite a few have a pale greenish-tinged bill, a colour not usually seen in argenteus, but which is not unusual in argentatus-types.

Head- and breast-markings The dark head, neck and breast-markings of third-winter types average heavier and more blotchy than in European Herring Gulls, especially argentatus, on which these markings tend to be paler and less extensive. On the most heavily marked birds, the density of dark spotting, especially on the hindneck and breast, is strikingly different from anything usually seen in Europe but a few 'dark’ sub-adult argenteus can be similar.

Primary pattern
a At rest: In line with their ’retarded' or ’immature’ look, many third-winter smithsonianus do not show any obvious white primary tips, while these are usually distinct in third-winter argenteus (at least on P6) and especially argentatus;
b ln flight: There is much overlap in the primary pattern, but a few third-winter smithsonianus, at least in Newfoundland, already show long grey tongues up to and including P10) (on which the tongue may reach down for half the feather length or even more along the inner web), while also showing a complete black band on P5, and sometimes even dark markings on P4 (Peter Adriaens in litt). If a third-winter bird with this type of primary pattern (best seen from below) also retains a lot of brown markings on the wing-coverts / tertials, the combination of all of these characters may be helpful. For instance, third-winter argenteus do not have such long grey tongues on P9-P10 (P10 normally does not have much of a grey tongue at all at this age), nor predominantly brown wing-coverts. Third-winter argentatus may show the long tongues and brown wing-coverts but will, in that case, be less inclined to show a complete black band on P5, and may have darker grey upperparts. While the primary pattern in third-winter birds is a complex character (eg, also because intergrades argenteus x argentatus have to be taken into account), it may be worth looking at and documenting when faced with a suspected third-winter smithsonianus in Europe.

We would like to emphasize that some third-winter smithsonianus can appear very similar to second-winter European Herring Gull. The problem / pitfall may be as follows: an observer may encounter a Herring Gull that attracts his attention because of its dark underparts and hindneck, dark greater coverts and tertials, a lot of dark in the tail, contrastingly pale grey saddle, etc. He may be tempted to believe that he is looking at a second-winter smithsonianus, but when he looks more closely, the tail is certainly not all-dark, and the upper- and undertail-coverts are hardly marked at all. Therefore, he dismisses the bird as an odd (dark) second-winter European Herring Gull - while in fact, it was a perfectly typical third-winter smithsonianus… Correct ageing is a critical first step in the identification process, but in third-winter birds, it may at times only be possible when the bird is seen in flight (when the inner primaries can be seen).

CONTINUE FOURTH WINTER AND OLDER

American Herring Gull (smithsonianus) 4cy, February 24 2008, St. John's, Newfoundland, Canada. Picture: Bruce Mactavish. Many immature markings, combined with deep pale tongues P6-P8 with black running along feather edge of outerweb; when full adult, this will develop into "bayonets".