Variation in immature American Herring Gulls

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A recent discussion about geographic variation in Herring Gulls (on the ID-Frontiers listserve) prompted me to go back and scan some photos I took in 1998 at Cape May. At the time I was sorting out what seemed to be two populations of Herring Gulls, identifiable in their first winter by plumage and shape. There is, of course, lots of confusing variation in Herring Gulls, but a few very sleek and fresh-plumaged immatures were readily distinguishable from the heavier, darker, and more worn local birds.

The photos below show one classic individual of this “pale” type, one intermediate, and several typical New Jersey birds.

This is the classic "pale" Herring Gull, with smooth pale gray-brown plumage, streaked breast, very pale face, neatly checkered wing coverts that show almost no signs of wear, and still essentially full juvenile plumage in late January. These birds also consistently looked overall more sleek and slender, with gently sloping forehead, long bill, long tapered rear-end, and slim body. Typically the bill was subtly two-toned with a dark pinkish base and blackish tip. They also tend to show a paler rump and more white on the base of the tail feathers. 28 Jan 1998, photo copyright David Sibley.
Same bird as above, 28 Jan 1998.
In contrast, here is a stocky, dark, and worn bird, typical of the first-winter Herring Gulls common in New Jersey. 30 Jan 1998, photo copyright David Sibley.
Another individual showing the dark, worn, and blotchy plumage of the common New Jersey Herring Gulls; although this one has fairly unworn wing coverts. Note the dark face, blotchy black bill, and overall heavier appearance. 23 Feb 1998, photo copyright David Sibley.
A fairly pale but otherwise typical first-winter Herring Gull of the common New Jersey form, with overall dark brown color, messy plumage a mixture of very worn juvenile feathers and new blotchy feathers, with dark face and mostly blackish bill. 4 Feb 1998, photo copyright David Sibley.
A bird showing mixed features. The sleek shape, white head, and neatly patterned and fresh-looking coverts all suggest the "pale" type, but the molt is more advanced with nearly all scapulars and some wing coverts replaced. 4 Feb 1998, photo copyright David Sibley.

One of the things that prompted me to start looking at these birds was seeing a first-winter Herring Gull at Cape May with lots of white at the base of the tail, more like the European subspecies. I called the first one a “European” Herring Gull, because it had an obvious tail band and also showed these other differences – sleek, neatly-checkered, pale-faced, pale rumped – and it was only after seeing two more and some intermediates that I started to think this was a variation of American Herring Gull.

Birds like the one in the first two photos above were scarce at Cape May. I saw up to three in a day, and probably about 10 individuals during the course of the winter of 1997-98. They appeared very late in the fall, with most seen in Jan-Feb. That was among a relatively small number of gulls present in Cape May Harbor. If I took a wild guess I would say that somewhere under 5% of all the first-winter gulls I saw were of this type.

Adults are less variable, and therefore harder to distinguish. I was able to pick out adults that were late to develop breeding colors in the spring, and assuming those were from farther north I looked at head streaking, wingtip pattern, and mantle color to see if I could find any consistent patterns, but with a small sample size and casual study I could not.

Figuring out where these birds come from, if they even have a “home range”, will be a real challenge and will require looking very carefully at a lot of gulls in a lot of places. New DNA studies point to possible subdivisions of North American Herring Gulls, and for someone with the time, energy, and meticulousness, this offers one of the better opportunities for discovery in North American birds.

4 thoughts on “Variation in immature American Herring Gulls”

  1. Hi David,
    Very interesting post. By sheer coincidence, Martin Garner from the UK also is talking about variability in European first winter Herring Gulls over at his website at Birding Frontiers. Thought you might want to check out his discussion as well. Good stuff!
    Thanks for posting.
    Jody Enck

  2. Hi
    I was using your bird guide to prepare for a show on id winter gulls,
    My question is about 1st winter herring gulls. What exactly is a first winter herring gull-
    Is it the first winter the gull experiences after it leaves the nest.
    The guide shows juvenile Aug-Nov then below 1st winter Sep-Apr.
    I’m assuming 1st winter is a one year old bird.
    Thanks for your help
    I enjoyed your guide
    John Heidecker

    1. Hi John, First winter means the first winter after the bird hatched, when it is around six months old. The dates indicated in the guide overlap because some individuals (long-distance migrants from far northern nesting sites) retain juvenal plumage until November or even longer, while other individuals (e.g. from relatively sedentary populations such as New England) molt from juvenal to first-winter plumage in September. Hope that helps.
      Best, David

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