Transfer Larus marinus from Hypothetical List to Main List
Effect on the SACC List: This transfers a species from the Hypothetical List to the Main List.
Background: The Hypothetical List currently reads:
Larus marinus Great Black-backed Gull: One unpublished photograph and one sight record from Aruba (Voous 1977, 1983) and one unpublished photo from French Guiana (fide A. Renaudier); sight record from northwestern Venezuela (Casler 1996); sight record from w. Colombia (Naranjo & Franke 1995). Two published photos from Trinidad (Kenefick 2010).
Kenefick’s 2010 rarity report reads: ‘A “near-adult” Greater Black-backed Gull, Larus marinus was photographed at Orange Valley on 31 January, 2009 (JM). It remained present until at least 21 March. This is the first record for Trinidad and Tobago. On 23 February, 2009, a first winter plumaged bird was found at the same site (MK); well watched and photographed until 9 July, 2009.’
Photographic evidence: Looking at the first photograph (p.83:1 – just email Van Remsen for pdf) we see a black-backed gull that could indicate L. marinus, L. fuscus fuscus, L. dominicanus, L. atlanticus, or L. belcheri. Importantly, the bird has pink tarsus, which rules out all but L. marinus because the others have yellow tarsus. The retention of a black subterminal bill band is from the third year, although the bird lacks a wing moult to attain adult plumage, so “near adult” is a fair description. The second photograph (p.83:2) shows a first year bird (all dark bill and pale head) with a nice direct comparison against Laughing Gulls Leucophaeus atricilla. The shear size of this bird, and thickness of the bill with a notable gonydeal angle immediately point to L. marinus and rule out all other gull species.
Recommendation: There are no doubts about the identification, there seems to be no controversy over the authenticity of the locality data notwithstanding that both were long staying birds. I recommend a YES vote to add this species to the main list as a vagrant to the region.
KENEFICK, M. 2010. Seventh report of the Trinidad and Tobago Rare Birds Committee: rare birds in Trinidad and Tobago 2009. J. Trinidad and Tobago Field Naturalists’ Club 2010: 78-83.
Mark Pearman, October 2011
Comments from Pacheco: “YES. Em vista das informações reunidas e do aval do Trinidad and Tobago Rare Birds Committee.”
Comments from Pérez: “YES. Published information confirms the presence of this species in the region.”
Comments from Jaramillo: “YES – I have seen photos of the 2009 bird, and it looked clearly like marinus based on structure, soft parts, back color and wing pattern.”
Comments from Zimmer: “YES. I agree with the analysis of the identity of the birds in the photographs.”