English and Scientific names:

Great Black-backed Gull (Larus marinus)

Number of individuals: 

One in first-cycle plumage

Locality: LOUISIANA: 

Jefferson Parish

Specific Locality:

East end of Grand Isle between Barataria Pass and spit of raised land to the west of U.S. Coast Guard property near terminus of Daminada Road.

Date(s) when observed:

24 February 2007

Time(s) of day when observed:  

Between 11:30 AM and 12:00 PM, and for a second time between 12:45 PM and 1:15 PM.

Reporting observer and address:

Justin Bosler
Baton Rouge, LA

Other observers accompanying reporter who also identified the bird(s):

Devin Bosler

Other observers who independently identified the bird(s)


Light conditions (position of bird in relation to shade and to direction and amount of light):

Nearly ideal lighting conditions with sun directly overhead shaded by a slight overcast.

Optical equipment: 

Nikon Venturer LX 8x32, good condition

Distance to bird(s): 

As close as 25 meters while hugging the shoreline out of Barataria Pass.

Duration of observation:

Total time of observation amounts to approximately one hour.


Littoral zone, sandy beach, and shelled lot.

Behavior of bird: 

The gull was initially spotted in flight as it came through Barataria Pass. Devin Bosler was able to obtain video of the gull in flight at this point. After continuing 150 meters or so west down the beach, the gull landed and began preening and foraging in the surf with a few Herring Gulls. Less than an hour later, the gull was resting on a shelled lot on the outer perimeter of a congregation of gulls and skimmers.


Massive, barrel-chested gull in first-cycle plumage. Head large and bulky with flat-topped appearance on thick neck. Head feathering primarily white with dark feathers coalescing around the eye. Underparts were white with minimal dark streaking and smudging on neck, breast, belly, and flanks. Mantle and scapulars showing some transitional gray, dark terminal-banded feathers that contrasted with the dark brown chequered upperwing coverts. Secondaries were dark brown and contrasted with the paler greater secondary coverts when in flight. Tertials were very dark brown with a considerable pale margin. Outer primaries were entirely black, while inner primaries were less intensely shaded, giving the appearance of a pale window when in flight. Tail was patterned with messy, dark brown bars and rump was only marginally marked with brown. Bill was massive and bulbous-tipped. Upper mandible and lower mandible black fading to horn-brown on extreme base. Upper mandible was ivory-tipped. Irides were medium to dark brown. Legs were fleshy-pink.


Voice was not heard.

Similar species:

Lesser Black-backed Gull eliminated by overall size, bill size and shape, and primary length, as well as other minor differences in the coloration of the upperwing coverts and scapulars. In flight, pale inner primary window also eliminates LBBG.

Photographs or tape recordings obtained?

Video taken by Devin Bosler. Photographs taken by Justin Bosler.

Previous experience with this species: 

Extensive experience with this species.

Identification aids:


This description is written from: 

Description written from memory and notes taken during observation.

Are you positive of your identification? If not, explain: 


I am 100% positive of the ID.


Justin Bosler

Date and time: 

16 March 2007; 10:26 PM