Adult American Herring Gulls, seen from a Dutch perspective – 201402

One of the main reasons for my gull watching trip to Chicago, USA, last February was to get familiar with adult American Herring Gull Larus smithsonianus and to learn more about their differences with the European Herring Gulls Larus argentatus argenteus that I observe in the Netherlands.

Adult American Herring Gull. Lake County Fairground, Libertyville, Illinois, USA. 18 February 2014.

In this blog post I will go through some of the features in the adult American Herring Gulls that I observed in the southern Lake Michigan region and compare them with those of adult European Herring Gull.

Disclaimer: this blog post is nothing more than a personal exercise in learning about the differences between American and European Herring Gull by studying the gulls that I saw in America. In no way am I claiming this to be a definitive guide for identifying an American Herring Gull in Europe. Having said that, I hope this post can be useful for other European birders to learn what characteristics to look out for when they come across a candidate adult American Herring Gull in Europe.

As a reference, I use the excellent article Identification of adult American Herring Gull by Peter Adriaens & Bruce Mactavish, as published in Dutch Birding 26-3, 2004. Note that in this article, the characteristics of Herring Gulls as seen in Newfoundland are described. These are most likely to occur in Europe, but their characteristics may vary with Herring Gulls of western USA.

I will use the 3 characters mentioned in the article that when used in combination should help in identifying an American Herring Gull in a European context:

1. Coloration of upper parts
2. Pattern on P10
3. Pattern on P5

I will also take a look at the following supporting characters:

• Grey mirror on underside of P9/P10
• Black spots on upper secondaries
• Mirror on P9
• Pattern on P7 and P8

Coloration of upper parts

The grey tone of adult American Herring Gull is similar to or slightly paler than that of European Herring Gull L. a. argenteus. (Kodak grey-scale value: Newfoundland American Herring Gull (3)2.5-4.5, European Herring Gull 5.0-5.5).

I found it very difficult to see the upper part coloration of the American Herring Gulls that I observed as anything different from what I am used to seeing in the Netherlands. The difference is probably so minimal that it is only noticeable when seeing the 2 species side by side.

Pattern on P10

The pattern on the under side of P10 is a helpful tool to distinguish adult American Herring Gull from adult European Herring Gull.

Most useful is the length and shape of the tongue on the underside of P10.

Note: Although the upper side of P10 shows the same pattern as that of the under side, it is much more difficult to see because P9 obscures the inner web of P10. None of the photos that I took showed the inner web pattern on the upper side of P10.

In Newfoundland American Herring Gull, the tongue on P10 is said to be long (more than half the length of the inner web), broad and steeply angled (about 90 degrees).

As a result, the length of the remaining black medial band is the same length as the length of the mirror.

In addition, American Herring Gull combines the tongue shape with a variable amount of black between the mirror and the tip of the feather, ranging from just a small spot to a complete band.

In contrast, European Herring Gull Larus argentatus argenteus has a short tongue with an oblique angle and a medial band that is longer than the length of the mirror. (Note that the P10 pattern of Eastern Baltic Herring Gull Larus argentatus argentatus can resemble that of American Herring Gull. Also, those European Herring Gulls that do show a long tongue usually combine this with a completely white feather tip.)

For those of you who are unfamiliar with these terms, refer to the following figure:

When checking this characteristic in some of the adult birds that I photographed in the southern Lake Michigan region in the USA in February 2014, most individuals did indeed show a long tongue. However, the tongue was not long enough to result in a medial band that was shorter than the length of the mirror. This could indicate that the birds that I saw originated from a different location than those described in the referenced article.

Also, as ever with gulls, variation is high and I also came across individuals that showed a short tongue with an oblique angle (comparable to the pattern of European Herring Gull).

The following collection of images shows the variation among the gulls that I observed:

Under side of P10 in American Herring Gulls.

One of the advantages of the long tongue is that it is visible in birds in rest and can therefore be used as an early indication for picking out an American Herring Gull in a group of European Herring Gulls.

18 February 2014. Lake County Fairground, Libertyville, Illinois, USA.

18 February 2014. Lake County Fairground, Libertyville, Illinois, USA. Rather odd looking individual with an extremely long tongue, leaving no room for a mirror. Unfortunately I don’t have a photo of an open wing which would have been interesting to see.

Pattern on P5

Perhaps the most well known feature of adult American Herring Gulls among European birders is the pattern on P5: the classic black band across both webs composed of 3 pointed wedges which together form a distinct ‘W’ shape.

This turned out to be a consistent characteristic in the individuals that I photographed and in which P5 was visible: all showed this pattern except for 2 individuals which showed an interrupted black band (but still in a W shape).

While a minority of European Herring Gulls can also show a W-pattern on P5, the common pattern for them is to have just a single black mark on the outer web.

Putting it all together

As the referenced article states: positively identifying an adult American Herring Gull in a European context is difficult at best and should never be based on a single character.

Especially while observing resting American Herring Gulls in full alternate plumage (meaning completely white heads without any streaking), I personally found it difficult to see any clear differences between them and European Herring Gulls.

However, those individuals that were in basic (winter) plumage showed more streaking in the neck and on the breast than the average European Herring Gulls that I come across.

As far as overall structure, bill coloration and bill pattern is concerned, I also could not detect any differences with what I’m used to seeing and I therefore did not get the feeling that I was looking at a distinctly different species of Herring Gull. This can probably be put down to the huge variation that exists within each species, including between that of males and females.

For me, the distinguishing characters could only be found in the primary pattern: a combination of a long tongue on P10 and the presence of a clear W on P5.

I also noticed that a black mark on the outer web of P4 was much more common in adult American Herring Gull than what I am used to seeing in adult European Herring Gulls.

Would you notice if I would put a European location in the caption of this photo? Lake County Fairground, Libertyville, Illinois. 18 February 2014.

15 February 2014, North Point Marina, Winthrop Harbor, Illinois, USA. A typical adult American Herring Gull of my trip: P10 with a sharply angled, long tongue and much black between the mirror and the tip, and P5 with a distinct W. Note also the small black mark on the outer web of P4.

Supporting features

Apart from the 3 main features for identifying adult American Herring Gull described above, additional but less diagnostic features can also come into play:

• Grey mirror on underside of P9/P10
• Black spots on upper secondaries
• Mirror on P9
• Pattern on P7 and P8

Grey mirror on underside of P9/P10

In a recent article by Peter Adriaens on birdingforntiers.com (A new feature for identifying adult American Herring Gull), a new distinguishing feature is reported: that of a grey mirror on the underside of P9 or P10. It is described as ‘a sort of isolated grey spot or grey hole inside the black(ish) pattern on the underside of P9 or P10’.

Two versions of it exist: a grey mirror which is completely surrounded by the surrounding black, and a grey cut which is open at the edge of the feather.

This feature is rare in European Herring Gull but has been seen in a few hybrids (or backcrosses) of Glaucous Gull x Herring Gull in Iceland.

I have never seen it myself in the European Herring Gulls that I have observed in the Netherlands.

Although this feature only occurs in a minority of American Herring Gulls and may even be present in one wing only, it could be used as a new feature for identifying adult American Herring Gull in a European context as the article states.

I noticed this feature in several American Herring Gulls, as the photos below show.

16 February 2014, BP Whiting refinery, Indiana, USA. Individual with a grey cut on P10 in the right wing only.

16 February 2014, BP Whiting refinery, Indiana, USA. Individual with a grey mirror on P9 in the left wing.

18 February 2014. Lake County Fairground, Libertyville, Illinois, USA. Individual with grey mirrors on P10 in both wings.

18 February 2014. Lake County Fairground, Libertyville, Illinois, USA. Individual with small grey mirror in P10 on left wing only.

Black spots on upper secondaries

Another character which is currently being investigated (by Leon Edelaar en Peter Adriaens) as a supporting feature of adult American Herring Gulls is the presence of very small black spots on the upper secondaries. (See American Herring Gull – in the Netherlands?)

These spots are very likely a remnant of the dark markings on the secondaries that are present in 4th-calendar year Herring Gulls (more on those in a later blog post).

I have not come across any adult American Herring Gulls that show this feature but it is certainly interesting to keep an eye on. I have also never observed this in European Herring Gulls.

Mirror on P9

Noticeable in the American Herring Gulls that I observed was the absence of a mirror on P9. Only in a handful of individuals did I come across this (see Adult American Herring Gulls, Lake Michigan region – 201402) whereas it is a common feature in the European Herring Gulls that I am used to seeing in the Netherlands.

Pattern on P7 and P8

The pattern on P7 and P8 for Newfoundland American Herring Gulls is described in the referenced article as a combination of a very long tongue (>3/4 of the visible part of the inner web) with a broad white tongue tip and a relatively thin black subterminal black band.  The outer web shows a distinct ‘bayonet’ pattern, described as ‘a thin, very pointed black wedge along the outer edge’.

I did not come across this combination of characteristics in most of the individuals that I photographed, indicating perhaps once more that these originate from somewhere else than Newfoundland.

P7 and P8 pattern in adult American Herring Gull.

Summary

I have found this first introduction to American Herring Gulls very intriguing and it has made me eager to find out more about the geographical differences of this species across the USA. Hopefully more visits to the USA will follow that will allow me to continue to study this gull.

References

Identification of adult American Herring Gull by Peter Adriaens & Bruce Mactavish, Dutch Birding 26-3, 2004

Identification of American Herring Gull in a western European context by Pat Lonergan & Killian Mullarney, utch Birding 26-1, 2004