1. English and Scientific names:  Great Black-backed Gull (Larus marinus)


2. Number of individuals, sexes, ages, general plumage (e.g., 2 in alternate plumage):  One in second cycle plumage

3. Locality: LOUISIANA: (parish)  Plaquemines

Specific Locality: East Grand Terre, Grand Terre Islands, ca. 5.0 mi. E of Grand Isle


4. Date(s) when observed: 15 March 2011

5. Time(s) of day when observed: 12:30 PM CDT

6. Reporting observer and address:  Justin Bosler

                                                    2415 Darnall Rd.

                                                    New Iberia, LA 70560

7. Other observers accompanying reporter who also identified the bird(s):  None

8. Other observers who independently identified the bird(s):  None

9. Light conditions (position of bird in relation to shade and to direction and amount of light):  Clear sky with optimal midday sunlight. Sun on back of observer. No glare or backlighting.

10. Optical equipment (type, power, condition): Nikon EDG 8x42 binocular (good condition)

11. Distance to bird(s): 50 meters

12. Duration of observation: about 5 minutes

13. Habitat:  Open beach of barrier island on Gulf of Mexico

14. Behavior of bird / circumstances of observation (flying, feeding, resting; include and stress habits used in identification; relate events surrounding observation):

Gull was resting and preening on beach by itself away from the loafing flock of larids.

15. Description (include only what was actually seen, not what "should" have been seen; include if possible: total length/relative size compared to other familiar species, body bulk, shape, proportions, bill, eye, leg, and plumage characteristics. Stress features that separate it from similar species): Large, white-headed gull with barrel chest and thick neck, large, mostly white and relatively squared (gently sloping) head, beady, dark honey eyes, dark upperparts with a mix of fresh, slaty and worn, mottled scapulars and worn, mottled wing coverts, dark brown tertials with fairly broad white tips and few internal pale markings, proportionately short, blackish primaries, mostly white underparts, massive, bulbous-tipped bill with basal 2/3 flesh and distal 1/3 black with ivory tip and black edging along tomia, flesh legs with pinkish-flesh feet. Tail appeared mostly white basally and blackish distally, but poorly seen.

16. Voice:  None

17. Similar species (include how they were eliminated by your observation):

Lesser Black-backed Gull (L. f. graellsii) eliminated by overall size, massive, bulbous-tipped bill, mostly white and relatively flat (or squared) head, short primary projection, dark, beady eyes placed toward upper center of face, and fleshy legs. Great Black-backed x Herring Gull (L. smithsonianus) hybrid eliminated by massive bill, large, squared head, dark, beady eyes placed toward upper center of face, mostly white below, and fresh, slate gray scapulars and boldly marked greater coverts with dark, subterminal anchors. Slaty-backed Gull (L. schistisagus) eliminated by squared head, massive bill with pronounced gonydeal expansion, overall clean-looking appearance, nearly unmarked whitish head and underparts, dark subterminal markings on greater coverts, and flesh legs. Slaty-backed also has a more squat appearance. Kelp Gull (L. dominicanus) eliminated by large, squared head with beady eyes placed high on face, fresh, slate gray scapulars, mottled (vs. uniform) wing coverts, relatively short primary projection, and flesh legs, etc.

18. Photographs or tape recordings obtained? (by whom? attached?):  Photos obtained by Justin Bosler and attached.

19. Previous experience with this species:  Extensive experience across its normal range on the East Coast as well as multiple individuals in LA.

20. Identification aids: (list books, illustrations, other birders, etc. used in identification):

a. at time of observation:  None

b. after observation:  None

21. This description is written from: _____ notes made during the observation (_____notes attached?);__X__notes made after the observation (date: 15 Mar 2011); ___X__memory.

22. Are you positive of your identification if not, explain:  Yes, 100% positive.

23. Signature of reporter:  Justin Bosler   Date: 31 March 2011   Time:  4:00 PM CDT