GULLS Thayer's
Western
Temp 3
Temp 4
Temp 5

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smithsonianus - AMERICAN HERRING GULL

Much of gull discussion is based on personal experience and opinion, but few resources are available either in print or on the Internet that tackle the issue of individual variation in gulls. This is what I have started to tackle in these pages, illustrated with many photos. I hope you all find it useful.

First cycle - Juvenile/first basic.

SMITH1- OCT. 31, 2003. Half Moon Bay, SM, California. A. Jaramillo

SMITH1 is a pretty typical bird of this age. Smith1 shows approximately 40% first basic upperparts. Note that some retain full juvenile plumage until much later on in the fall/winter. There also appears to be two extremes, a chocolate brown bird that keeps a black bill until later on in the season, and a paler group that obtains a pink bill base earlier than the dark group. Intermediates are of course present as well, but the extremes are very distinct. As is typical with smithsonianus, the primaries are blackish and the background colour of the tertials is similar to the primaries. Tertials are nicely notched, particularly towards the tip. The classic contrasting paler head of smithsonianus is starting to show up on this bird.

SMITH2 is a paler bird than SMITH1, but only two weeks later on in the year. These paler birds tend to have a whiter head than the dark ones, and more extensive pink at the bill base. The difference may be due individual variation, or perhaps these are birds from different populations, either an earlier nesting (pale) group, and a later nesting (dark) group or geographic variation in darkness independent of breeding times. These are open questions that reqire investigation.

SMITH3 is one of the darker birds, a classic one as a matter of fact. Note that this bird was photographed on the same day as SMITH2, but they are quite different in appearance. SMITH3 is still in full juvenal plumage. These smithsonianus that retain juvenal plumage may remind one of a dark Thayer's Gull, but look at how blackish the tertials are on this bird. Similar aged Thayer's shows tertials that are distinctly paler in background colour than the primaries. The dark centered scapulars, lacking any complex pattern are typical. The other bird in the photo is a small billed first cycle Glaucous-winged Gull.

SMITH4 is very similar to SMITH3, but notice that the bill has a more developed pale base, and most of the juvenal mantle feathers have been moulted out. SMITH4 is a bit more worn, and is beginning to show a paler-headed appearance. All of these individuals (1-4) show the typical dark based greater coverts of first cycle smithsonianus. This individual shows the classic smithonianus bill, which is long, but moderately thick, with a noticeable but not extreme gonydeal angle.

SMITH5 is a crisp juvenile, and a classic smthisonianus. The tertials look a little pale, but that may be the lighting. Compare this bird to SMITH3, which is another full juvenile. Compared to #3, SMITH5 is more patterned, this is particularly obvious on the lower scapulars which have broad pale spots along their edges, and thte tertials which are barred at their tips. Also look at the inner greater coverts, which are well barred to the base.

SMITH6 is an odd one. I don't know for sure that this is a smithsonianus. First of all it was a rather contrasting bird, witht well marked coverts and a pale head. The bill was stout, and structurally this bird looked chunky and shorter winged than a classic smithsonianus. Its upperparts are well advanced, being largely or entirely in first basic plumage. The dark anchor shaped markings on lower scapulars are not typical of smith. In many ways this individual is tending towards a Vega gull, but note that it has a black tail, to the base. It is birds like these which overlap with vegae, and will confuse the identification of that taxon along the Pacific coast. The very blackish primaries, tail and tertials do not suggest hybridization with Glaucous-winged or Glaucous gulls.