Proposal (667) to South American Classification Committee

Add Chroicocephalus philadelphia (Bonaparte’s Gull) to main list

A single bird in non-breeding plumage was photographed by D. M. Brinkhuizen, B. Haase and J. Nilsson at San Pablo estuary, Santa Province, southwest Ecuador (Nilsson et al. 2014). The bird was observed from 12-14 November 2013.

Detailed description and photograph corroborate its identity.

The following is a summary of the submitted description: White head with distinct black circular ear-patch, light grey mantle and neck, white underparts. Dark brown tertials, blackish primaries and tail band. It was smaller than the common local resident Grey-hooded Gull Chroicocephalus cirrocephalus and slightly smaller than most Franklin’s Gulls (Leucophaeus pipixcan), a common transient. Slender, all dark bill; dark eyes with broken eye-ring; pale pink legs. Most similar to first-year C. cirrocephalus because of distinct dark round auricular patch, but it was smaller, more elegantly shaped, with all black slender bill (which was reddish/orange base in juvenile C. cirrocephalus). Nearly similar in size to L. pipixcan but with a different head pattern (ear patch only) and a lighter mantle. Slender black bill, pink legs and white underwing exclude European Black-headed Gull (Chroicocephalus ridibundus), which is actually very unlikely to show up as vagrant in South America.

First documented record for Ecuador and 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.

Juan Freile, February 2014

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Comments from Jaramillo: “YES. Although I must admit shock, as I had assumed there were previous records in South America. Otherwise I would have alerted the observers of a record in Chile of the even greater magnitude of their find, which would then be the first record for South America as the bird was first found in Feb of 2014, months earlier than the Ecuador record. It was published with photo in the “Chiricoca” online magazine. But here are some photos of the bird to support that the species has occurred in South America: http://www.avesdechile.cl/545.htm”

Comments from Stotz: “YES. This picture is identifiable, and the Chilean photo that Alvaro added provides further support.”

Comments from Zimmer: “YES. The single photo and description provided confirm the identity of the bird from Ecuador, and the additional photos from Chile provided by Alvaro provide further justification for adding the species to the South American list.”

Comments from Stiles: “YES. This photo constitutes much stronger evidence for adding philadelphia to the main list.”