delawarensis Ring-billed Gull

(last update: 10-03-2014 )

Keith Mueller
Amar Ayyash
Mars Muusse

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Ring-billed Gull delawarensis juvenile, July 26 2013, Chicago, IL. Picture: Amar Ayyash.

See Amar's blog.

Juvenile Ring-billed Gulls (Larus delawarensis) are quite distinctive within their range, but anyone who's ever spent a little time observing this age group quickly comes to the realization that characterizing a "typical" youngster is no simple task.

Two juvenile types that may be thought of as opposite points along a spectrum. The following examples are limited to individuals thought to be from one to three colonies near the Chicago lakefront (all within an approximate 15 mile radius). Fledglings in this region begin to appear in late June and peak in late July.

Two Types:

Ghost-type (1) - As the name implies, this aspect is notably pale with a strong white ground color. The underparts, head and neck tend to show limited brown washing. The scapular feathers usually show an indistinct pattern. They're often boldly edged and based with white, giving the brown centers a golden appearance. The tertials can show a considerable amount of white, especially closer to the tips and along the edges, and the primaries are more likely to show pale tips; Both of these feather groups can show an intricate pattern of dark subterminal diamonds surrounded by white notches. 

Brown-type (2) - The general appearance of this type is a dark, chocolate-brown aspect. The most distinctive feature of this group is the large scapulars with solidly dark centers. The tertials are mostly plain and resemble the scapulars but are often a few shades darker. The greater coverts are more likely to show an even silver-gray throughout. The primaries are less often tipped with white compared to ghost-types. The underparts, head and neck show varying degrees of dark wash (this feature varies considerably and might be influenced by fading, wear and the onset of the first prealternate molt). Finally, I would suggest that this group is more likely to first acquire gray post-juvenile scapulars and upperwing coverts in late summer.

An important note here is that the aspects of these plumages quickly become altered shortly after the summer months due to the expected consequences of wear, bleaching and the commencement of the prealternate molt. And these two types appear to be on opposite ends of a variable spectrum- a spectrum that should be thought of as a work-in-progress.

Below: brown type example. This brown-type also shows large dark centers on the scapulars. The tertials are plain and are a few shades darker here. The greater coverts are mostly gray. Also note the lack of any notable white edging to the primaries.