Proposal (668) to South American Classification Committee

 

Add Larus californicus (California Gull) to main list

A single bird in first winter plumage was first located on 14 February 2014 by K. Terán and several other observers at Yaguarcocha Lake, Imbabura Province, northern Ecuador (Nilsson et al. 2014). It remained at the same site until 5 March 2014 and was observed and photographed by several other birders.

Pale brown above, including upperwing; dense whitish mottling above. Underparts dull whitish with brownish mottling; rump paler than remaining upperparts; blackish tail and primaries. In flight: more uniform pale upperparts than Herring Gull (Larus argentatus smithsonianus), tail more uniformly black. Pink bill tipped dark, pinkish legs. Bill is medium sized, with parallel sides, less stout than in L. argentatus. Wing projection is larger than in similar L. argentatus.

There is a single previous record from Ecuador: a detailed but undocumented observation from Santa Elena Peninsula (Ridgely & Greenfield 2001). First documented record for South America.

Ref:

Nilsson, J., J. F. Freile, R. Ahlman, D. M. Brinkhuizen, P. J. Greenfield & A. Solano-Ugalde. 2014. Rare birds in Ecuador: second annual report of the Committee for Ecuadorian Records in Ornithology (CERO). Avances en Ciencias e Ingenierías 6(2): B38-B50.

Ridgely, R. S. & P. J. Greenfield. 2001. Birds of Ecuador. Cornell Univ. Press, Ithaca, NY.

 

 

Juan Freile, February 2014

 

 

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Comments from Jaramillo: “YES – The features that are important are: 1) dark inner primaries 2) dark tail 3) bicolored bill 4) dark and relatively unmarked greater coverts. Identification is most problematic from smithsonianus Herring Gull, and to a lesser extent (no pun intended) from Lesser Black-backed Gull. But the photos identify the bird as a California Gull, particularly due to the wing pattern, vs. smithsonianus, and tail pattern vs. L. fuscus.”

 

Comments from Zimmer: “YES, although only based upon what can be seen in the (not great) photo, and not from the rather scanty and misleading description (“more uniform pale upperparts than Herring Gull”).  I would echo Alvaro’s analysis of the key distinguishing features, and add that the neatly black-tipped, mostly pinkish bill is typical for 1st-cycle California Gulls, and atypical for like-aged smithsonianus Herring Gulls.”

 

Comments from Stiles: “YES. I defer to Alvaro on this, as I am not an expert on gulls (living in landlocked Bogotá).”

 

Comments solicited from Jon Dunn: “I judge the photo from Yaguarcocha Lake, Imbabura Province, northern Ecuador, to be a first cycle California Gull, a conclusion reached by the finding observers.  I agree with their analysis, noting the rather small parallel-sided bill that is bi-colored.  The bill shape of our North American smithsonianus, is more robust overall.  One feature not addressed by the reporting observers, but it is clinching for me is the lack of a pale inner primary panel.  Our Herring Gull, as well as European subspecies of Herring, has a pale inner panel on the primaries.  This is almost completely lacking in first and second cycle California Gulls, and in the one photo I evaluated, the entire upper wing is shown nicely, and it looks to my eye just perfect for California.  Young California Gulls have a very dark ‘hand.’  There may some Old World taxon of Herring Gull (e.g. armenicus) that may have a similar wing pattern.  I haven’t researched all of the ‘Herring’ taxa for wing patterns of immatures, but this seems highly improbable, and as noted the wing pattern fits California very closely.  Another feature, young first cycle California Gulls by mid and late winter look smudgy, while first cycle Herring Gulls through the first winter look neater, somewhat more scaly, etc., at least the ones that appear in western North America, in general representing a later onset for the breeding season.  Young California Gulls are moving around by mid-July, and appear sometimes far from breeding areas on that date.  In other words by late winter they could appear quite worn appearing.  I would add, of course, that some first cycle Herring Gulls, even in early winter, have a bi-colored bills, much like Herring, although again the shape of the bill is different, and the line of separation of pink and dark (more even in Herring) is slightly different.  As noted, bills are tricky, concentrate on that inner wing panel.  Trust a note will be published somewhere, perhaps in Cotinga?”